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Presenting at UKOUG Techfest19 Conference in Brighton, UK September 13, 2019

Posted by Richard Foote in Techfest19.
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I’m very excited to be attending my 3rd UKOUG Conference, this year re-badged as Techfest19. The fact it’s being held in Brighton is a little disconcerting for a Crystal Palace fan, but really looking forward nonetheless to what has always been one of the very best Oracle conferences on the yearly calendar.

I have a number of presentations and Roundtable sessions that I’ll be participating in (follow the links to find the session abstracts):

 

I was very honoured after my 2nd attendance in Birmingham to have been awarded a “Lifetime Achievement Award” by the UKOUG, so I feel the duty bound to make sure my presentations are “top-shelf”.

Really looking forward to catching up with all my UK/European Oracle friends, please say hello if you see me (I’ll be the one wearing the Crystal Palace football jersey) ūüôā

 

 

 

 

Announcement: Australia/NZ “Let’s Talk Database” Events October 2019 !! September 12, 2019

Posted by Richard Foote in 19c, Automatic Indexing, Exadata X8, Let's Talk Database.
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I’ve very excited to announce the next series of Oracle “Let’s Talk Database” events to be run throughout Australia and New Zealand in October 2019.

I’ll be discussing two exciting topics this series, “Oracle Database 19c New Features” and “Oracle Exadata X8“.¬†As always, these sessions run between 9am-1pm, include a networking lunch and are free, but you MUST register to attend.

Dates, locations and registration links are as follows (Note the Sydney location is NOT the Oracle office in North Ryde):

Canberra:     22 October РRegistration Link (Oracle Canberra Office)

Sydney:       23 October РRegistration Link (Stone and Chalk, York St)

Melbourne: 24 October – Registration Link (Oracle Melbourne Office)

Brisbane:     29 October РRegistration Link (Oracle Brisbane Office)

Auckland:    30 October РRegistration Link (Level 13, AMP Centre, 29 Customs Street West)

Wellington: 31 October – Registration Link (Oracle Wellington Office)

 

Session details as follows:

Oracle Database 19c New Features

The latest Oracle Database Release 19c has introduced many exciting new features and enhanced capabilities that will be of much interest to both DBAs and Developers. This session will discuss in some detail a number of these new features with practical examples on how they can assist Oracle professionals maximize the benefits of the Oracle Database, especially in relation to Oracle Cloud and Oracle Engineered Systems deployments. New features discussed include Hybrid Table Partitions, Active Standby DML Redirect, Real Time Statistics, High-Frequency Automatic Optimizer Statistics Collection, SQL Quarantine,  new JSON Enhancements, DISTINCT option for LISTAGG aggregate and the most exciting new feature for some time, Automatic Indexing.

 

Oracle Exadata X8

The Oracle Exadata X8 Database Machine is the latest release in Oracle’s engineered systems platform designed specifically to deliver dramatically better performance, cost effectiveness, and availability for Oracle databases. This session will discuss various expanded and new capabilities introduced with Oracle Exadata X8 such as the new Exadata Extended Storage server, automated CPU, Memory and Network monitoring, advanced intrusion detection and Docker support. The session also examines why the Exadata Platform is so critical for the Autonomous Database Cloud Services and the unique Oracle Database19c capabilities such as Memoptimized Rowstore, Automatic Indexing, Real-Time Statistics and SQL Quarantine that are supported on Exadata.

 

So plenty of exciting Oracle database stuff to discuss. Hope to catch you at one of these events !!

Oracle Database 19c Automatic Indexing: Default Index Column Order Part II (Future Legend) September 11, 2019

Posted by Richard Foote in 19c, 19c New Features, Automatic Indexing, Clustering Factor, Index Column Order.
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In Part I, we explored some options that Oracle might adopt when ordering the columns within an Automatic Index by default, in the absence of other factors where there is only the one SQL statement to be concerned with.

A point worth making is that if all columns of an index are specified within SQL equality predicates, then the ordering of columns within an index is of little consequence. I’ve discussed this point a number of times previously.

Let’s explore if perhaps the resultant Clustering Factor of an index might be a factor in the default Automatic Index column order.

I begin by creating a table that has two columns of interest, CODE1 which is poorly clustered and CODE2 which is very well clustered:

SQL> create table muse (id number, code2 number, code1 number, name varchar2(42));

Table created.

SQL> create sequence muse_seq;

Sequence created.

SQL> create or replace procedure pop_muse as
begin
  for code1_value in 1..10000 loop
     for i in 1..100 loop
        insert into muse values (muse_seq.nextval, ceil(dbms_random.value(0,100)), code1_value, 'Back Holes');
     end loop;
   end loop;
   commit;
end;
/

Procedure created.

SQL> exec pop_muse

PL/SQL procedure successfully completed.

SQL> exec dbms_stats.gather_table_stats(ownname=>null, tabname=>'MUSE');

 

We then run the following query in which to hopefully create an Automatic Index on both CODE1 and CODE2 columns:

 

SQL> select * from muse where code1=406 and code2=83;

15 rows selected.

 

If we wait for the Automatic Index to be created and check out the Automatic Index report:

 

INDEX DETAILS
-------------------------------------------------------------------------------
  1 The following indexes were created:
*: invisible

----------------------------------------------------------------------------
| Owner | Table | Index                | Key         | Type   | Properties |
----------------------------------------------------------------------------
| BOWIE | MUSE  | SYS_AI_c1m8fkukj1368 | CODE2,CODE1 | B-TREE | NONE       |
----------------------------------------------------------------------------

VERIFICATION DETAILS
-------------------------------------------------------------------------------
1 The performance of the following statements improved:
-------------------------------------------------------------------------------

Parsing Schema Name  : BOWIE

SQL ID               : 0pdqsvpggupnz

SQL Text             : select * from muse where code1=406 and code2=83

Improvement Factor   : 4092.8x

 

SQL> select index_name, column_name, column_position from user_ind_columns
     where table_name='MUSE' order by index_name, column_position;

INDEX_NAME             COLUMN_NAME          COLUMN_POSITION
---------------------- -------------------- ---------------
SYS_AI_c1m8fkukj1368   CODE2                              1
SYS_AI_c1m8fkukj1368   CODE1                              2

 

We notice the index is created in CODE2, CODE1 column order.

If we create a manual index with the column order reversed:

 

SQL> create index muse_code1_code2_i on muse(code1, code2);

Index created.

SQL> select index_name, auto, constraint_index, visibility, compression, status, num_rows, leaf_blocks, clustering_factor
     from user_indexes where table_name='MUSE';

INDEX_NAME             AUT CON VISIBILIT COMPRESSION   STATUS     NUM_ROWS LEAF_BLOCKS CLUSTERING_FACTOR
---------------------- --- --- --------- ------------- -------- ---------- ----------- -----------------
SYS_AI_c1m8fkukj1368   YES NO  VISIBLE   DISABLED      VALID       1000000        2506            362900
MUSE_CODE1_CODE2_I     NO  NO  VISIBLE   DISABLED      VALID       1000000        2510            129878

 

We notice that the manual index has the better resultant Clustering Factor. So the Clustering Factor doesn’t appear to be a factor in Automatic Index column order (no pun intended).

If we re-create the initial table in Part I, but this time with the columns defined in the table in reverse order:

 

SQL> create table major_tom3 (id number, code3 number, code2 number, code1 number, name varchar2(42));

Table created.

SQL> insert into major_tom3 select rownum, mod(rownum, 1000)+1, ceil(dbms_random.value(0, 100)), ceil(dbms_random.value(0, 10)),
'David Bowie' from dual connect by level  commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats(ownname=>null, tabname=>'MAJOR_TOM3');

PL/SQL procedure successfully completed.

 

If we again run the following query:

 

SQL> select * from major_tom3 where code3=4 and code2=42 and code1=42

...

 

And wait for the Automatic Index to be created and look at the resultant report:

 

INDEX DETAILS

-------------------------------------------------------------------------------
   1 The following indexes were created:
---------------------------------------------------------------------------------------
| Owner | Table      | Index                | Key               | Type   | Properties |
---------------------------------------------------------------------------------------
| BOWIE | MAJOR_TOM3 | SYS_AI_g6sw030tg5ba9 | CODE3,CODE2,CODE1 | B-TREE | NONE       |
---------------------------------------------------------------------------------------

VERIFICATION DETAILS
-------------------------------------------------------------------------------
   1 The performance of the following statements improved:
-------------------------------------------------------------------------------

Parsing Schema Name  : BOWIE

SQL ID               : 22kts3uwj7kma

SQL Text             : select * from major_tom3 where code3=4 and code2=42 and code1=42

Improvement Factor   : 45854.1x

 

SQL> select i.index_name, i.column_name, i.column_position, t.num_distinct
from user_ind_columns i, user_tab_columns t
where i.table_name = t.table_name and i.column_name = t.column_name and i.table_name='MAJOR_TOM3'
order by i.index_name, i.column_position;

INDEX_NAME           COLUMN_NAME     COLUMN_POSITION NUM_DISTINCT
-------------------- --------------- --------------- ------------
SYS_AI_g6sw030tg5ba9 CODE3                         1         1000
SYS_AI_g6sw030tg5ba9 CODE2                         2          100
SYS_AI_g6sw030tg5ba9 CODE1                         3           10

 

We notice that the resultant Automatic Index has been created in CODE3, CODE2, CODE1 order.

After creating many many Automatic Indexes under all sorts of different scenarios, the DEFAULT behaviour is for Oracle to create Automatic Indexes in Column ID order (the order in which they are defined in the table definition).

Of course as we’ll see in future posts, if there are several conflicting SQL predicates, there are various other factors that govern a more appropriate Automatic Index order, but the fact that Oracle creates Automatic Indexes in Column ID order in the absence of other factors is useful to know.

As I said previously, if all indexed columns are specified in SQL equality predicates, index column order has little consequence. But as we’ll see in the next post, there are scenarios where index column order can be very important and this default index column order may not be the most optimal…

London March 2020: “Oracle Indexing Internals and Best Practices” and “Oracle Performance Diagnostics and Tuning” Seminars !! September 3, 2019

Posted by Richard Foote in Oracle Index Seminar, Oracle Indexes, Oracle Performance Diagnostics and Tuning Seminar.
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seminar photo

It’s with great excitement that I announce I’ll finally be returning to London, UK in March 2020 to run both of my highly acclaimed seminars. The dates and registration links are as follows:

23-24 March 2020: “Oracle Indexing Internals and Best Practices” seminar – Tickets and Registration Link

25-26 March 2020: “Oracle Performance Diagnostics and Tuning” Seminar – Tickets and Registration Link

You can also purchase tickets to both seminars at a special 20% combo discount:

23-26 March 2020:¬† Both “Oracle Indexing Internals and Best Practices” and “Oracle Performance Diagnostics and Tuning” Seminars – Tickets and Registration Link

The cost for each individual seminar is:

  • Early Bird Rate¬†(enrollments prior to 31 January 2020)¬†¬£990.00 (+ VAT)
  • General Rate¬† (enrollments post 31 January 2020)¬†¬£1190 (+VAT)

The cost for the seminar combo is:

  • Early Bird Rate¬†(enrollments prior to 31 January 2020)¬†¬£1550.00 (+ VAT)
  • General Rate¬† (enrollments post 31 January 2020)¬†¬£1900 (+VAT)

 

The venue is the rather nice Hilton London Kensington.

Prices include attendance to the seminar, both soft and hard copy of the extensive seminar materials, lunch and morning/afternoon tea/coffee.

Both seminars are very highly acclaimed, with past attendees universally applauding the quality and educational outcomes of the training.¬† They’re both aimed at Oracle Professionals (DBAs and Developers) who are interested in Performance Tuning and how to maximise the performance of both Oracle Databases and associated applications.

All the details of the Oracle Indexing Internals and Best Practices Seminar.

All the details of the Oracle Performance Diagnostic and Tuning Seminar.

Both seminars have strictly limited places to ensure a quality event for all attendees with venues booked with only small classes in mind. So I recommend booking early (as it’s cheaper) and to avoid possible disappointment. I don’t get to run these kind of events in the UK very often (it would be over 2 years since I last run seminars in London) so do take advantage of attending what will be a unique training opportunity while you can.

If you have any questions, please leave a comment or contact me at richard@richardfooteconsulting.com.

Hope to see you at one or both of these seminars next year !!

Oracle Database 19c Automatic Indexing: Default Index Column Order Part I (Anyway Anyhow Anywhere) September 2, 2019

Posted by Richard Foote in 19c, 19c New Features, Automatic Indexing, Index Column Order, Oracle Indexes.
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pin ups

The next thing I was curious about regarding Automatic Indexing was in which order would Oracle by default order the columns within an index. This can be a crucial decision with respect to the effectiveness of the index (but then again, may not be so crucial as well). Certainly one would expect the index column order be dependent on the SQL predicates running in the database and I’ll discuss all that in future posts, but what is the default behaviour here with regard index column order based (for now) on a single SQL predicate.

I could come up with a number of possible options that Oracle might adopt when determining the default index column order such as:

  • Column Name Order
  • Column ID Order
  • (Reverse) Column Cardinality Order
  • Best Clustering Factor
  • Other (Random even)

So to investigate this, I started with a basic table with 3 columns (CODE1, CODE2, CODE3) that had differing levels of cardinality:

SQL> create table major_tom (id number, code1 number, code2 number, code3 number, name varchar2(42));

Table created.

SQL> insert into major_tom select rownum, mod(rownum, 10)+1, ceil(dbms_random.value(0, 100)), ceil(dbms_random.value(0, 1000)), 'David Bowie' from dual connect by level  commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats(ownname=>null, tabname=>'MAJOR_TOM');

PL/SQL procedure successfully completed.

SQL> select column_name, num_distinct, density from user_tab_columns where table_name='MAJOR_TOM';

COLUMN_NAME          NUM_DISTINCT    DENSITY
-------------------- ------------ ----------
ID                        9914368 1.0086E-07
CODE1                          10  .00000005
CODE2                         100  .00000005
CODE3                        1000       .001
NAME                            1          1

I then ran the following query with a predicate based on the 3 columns CODE1, CODE2 and CODE3:

SQL> select * from major_tom where code3=42 and code2=42 and code1=4;

15 rows selected.

Execution Plan
------------------------------------------------------------------------------------------
| Id  | Operation                    | Name      | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |           |    10 |   280 |  7354   (7)| 00:00:01 |
|   1 |  PX COORDINATOR              |           |       |       |            |          |
|   2 |   PX SEND QC (RANDOM)        | :TQ10000  |    10 |   280 |  7354   (7)| 00:00:01 |
|   3 |    PX BLOCK ITERATOR         |           |    10 |   280 |  7354   (7)| 00:00:01 |
|*  4 |     TABLE ACCESS STORAGE FULL| MAJOR_TOM |    10 |   280 |  7354   (7)| 00:00:01 |
------------------------------------------------------------------------------------------

If we look at the resultant Automatic Index:

INDEX DETAILS

-------------------------------------------------------------------------------
1 . The following indexes were created:
--------------------------------------------------------------------------------------
| Owner | Table     | Index                | Key               | Type   | Properties |
--------------------------------------------------------------------------------------
| BOWIE | MAJOR_TOM | SYS_AI_9mrs058nrg9d5 | CODE1,CODE2,CODE3 | B-TREE | NONE       |
--------------------------------------------------------------------------------------

 

SQL> select i.index_name, i.column_name, i.column_position, t.num_distinct
from user_ind_columns i, user_tab_columns t
where i.table_name = t.table_name and i.column_name = t.column_name and i.table_name='MAJOR_TOM'
order by i.index_name, i.column_position;

INDEX_NAME           COLUMN_NAME     COLUMN_POSITION NUM_DISTINCT
-------------------- --------------- --------------- ------------
SYS_AI_9mrs058nrg9d5 CODE1                         1           10
SYS_AI_9mrs058nrg9d5 CODE2                         2          100
SYS_AI_9mrs058nrg9d5 CODE3                         3         1000

 

We notice that the Automatic Index is in CODE1, CODE2, CODE3 order.

If we create a similar table, but this time have the columns with a different order of cardinality:

SQL> create table major_tom2 (id number, code1 number, code2 number, code3 number, name varchar2(42));

Table created.

SQL> insert into major_tom2 select rownum, mod(rownum, 1000)+1, ceil(dbms_random.value(0, 100)), ceil(dbms_random.value(0, 10)),
'David Bowie' from dual connect by level;

SQL> commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats(ownname=>null, tabname=>'MAJOR_TOM2');

PL/SQL procedure successfully completed.

SQL> select * from major_tom where code3=42 and code2=42 and code1=4;

15 rows selected.

 

We notice that the resultant automatic index is still in the same CODE1, CODE2 and CODE3 order:

INDEX DETAILS

-------------------------------------------------------------------------------
1. The following indexes were created:
---------------------------------------------------------------------------------------
| Owner | Table      | Index                | Key               | Type   | Properties |
---------------------------------------------------------------------------------------
| BOWIE | MAJOR_TOM2 | SYS_AI_7w9t3tt9u171r | CODE1,CODE2,CODE3 | B-TREE | NONE       |
---------------------------------------------------------------------------------------

 

SQL> select i.index_name, i.column_name, i.column_position, t.num_distinct
from user_ind_columns i, user_tab_columns t
where i.table_name = t.table_name and i.column_name = t.column_name and i.table_name='MAJOR_TOM2'
order by i.index_name, i.column_position;

INDEX_NAME           COLUMN_NAME     COLUMN_POSITION NUM_DISTINCT
-------------------- --------------- --------------- ------------
SYS_AI_7w9t3tt9u171r CODE1                         1         1000
SYS_AI_7w9t3tt9u171r CODE2                         2          100
SYS_AI_7w9t3tt9u171r CODE3                         3           10

 

So we can eliminate column cardinality as being a contributing factor in Oracle deciding in which manner to order the indexed columns.

Which is unfortunate as we’ll see in a future post when we decide to implement Oracle Index Compression with Automatic Indexing.

In the next post, we’ll explore further other considerations and confirm how Oracle does indeed decide to order columns within an Automatic Index by default.

Announcement: New “Oracle Indexing Internals and Best Practices” Webinar – 19-23 November 2019 in USA Friendly Time Zone September 2, 2019

Posted by Richard Foote in Indexing Webinar.
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I‚Äôm very excited to announce a new Webinar series for my highly acclaimed ‚ÄúOracle Indexing Internals and Best Practices‚ÄĚ training event, running between 19-23 November 2019¬†!!

Indexes are fundamental to every Oracle database and are crucial for optimal performance. However, there’s an incredible amount of misconception, misunderstanding and pure myth regarding how Oracle indexes function and should be maintained. Many applications and databases are sub-optimal and run inefficiently primarily because an inappropriate indexing strategy has been implemented.

This webinar examines most available Oracle index structures/options and discusses in considerable detail how indexes function, how/when they should be used and how they should be maintained. A key component of the webinar is how indexes are costed and evaluated by the Cost Based Optimizer (CBO) and how appropriate data management practices are vital for an effective indexing strategy.  It also covers many useful tips and strategies to maximise the benefits of indexes on application/database performance and scalability, as well as in maximising Oracle database investments. Much of the material is exclusive to this seminar and is not generally available in Oracle documentation or in Oracle University courses.

For details of all the extensive content covered in the webinars, please visit my Indexing Seminar page.

The webinars will run for 4 hours each day, spanning a full week period (Monday to Friday) in a USA friendly time zone (it will actually be running Tuesday-Saturday in Australian time zones).

So that’s 15+ hours of extensive and practical content that will be of benefit to not only DBAs, but also to Developers, Solution Architects and anyone else interested in designing, developing or maintaining high performance Oracle-based applications.

The webinar series is scheduled as follows:

  • 19 ‚Äď 23 November 2019 (7am – 11am AEDT)

Note: Because of time zone differences, this will actually run between Monday 18 – Friday 22 November in the USA. The USA local running times will be between 3pm-7pm on the Eastern Coast and between 12pm-4pm on the Western Coast.

The cost of the 5 x day series will be $1500.00 Australian Dollars (+GST if applicable and attending from within Australia).

Note: Numbers are strictly limited to ensure the smooth running of these events and enable the opportunity for all attendees to ask questions. Some of my previous webinars have  officially been FULL, so please register early to avoid disappointment as webinars are not scheduled too regularly. 

Booking and Payment Instructions

You can pay for these webinars directly here if NOT attending from Australia:

Webinar Series: 19-23 November 2019 (7am AEDT – 11am AEDT): Buy Now Button

 

Alternatively if you’re attending from Australia or require an invoice, please email me at richard@richardfooteconsulting.comand I will send you an invoice with payment instructions. You can pay either by credit card via PayPal (you do not need a PayPal account for this), via a PayPal account or via direct bank transfer. Note: payment must be received before being registered for the webinar.

Once registered, you will be sent a unique link for each booking with instructions on how to attend the webinar. Prior to the webinar, you will also be sent a soft copy of the webinar materials, with 850+ pages of amazing content, that includes many useful tips and strategies to maximise the benefits of indexes on application/database performance and scalability.

Up to date details and terms and conditions can be found at my Indexing Webinar web page.

If you have any questions, please don’t hesitate to contact me.

Hopefully you can join us for what is always a rewarding training experience ūüôā

Oracle 19c Automatic Indexing: How Many Executions Does It Take? (One Shot) August 29, 2019

Posted by Richard Foote in 19c, 19c New Features, Automatic Indexing, Oracle Indexes.
2 comments

One shot single

One of the first questions I asked when playing with the new Oracle Database 19c Automatic Indexing feature was how many executions of an SQL does it take for a new index to be considered?

To find out, I create the following table:

SQL> create table bowie_one (id number constraint bowie_one_pk primary key, code number, name varchar2(42));

Table created.

SQL> insert into bowie_one select rownum, mod(rownum, 1000000)+1, 'David Bowie' from dual connect by level

SQL> commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats(ownname=>null, tabname=>'BOWIE_ONE');

PL/SQL procedure successfully completed.

I then ran the following query just once and checked to see if the Automatic Indexing task would pick this execution up and consider building a new index:

SQL> select * from bowie_one where code=42;

10 rows selected.

Execution Plan

------------------------------------------------------------------------------------------
| Id  | Operation                    | Name      | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |           |    10 |   230 |  6208   (7)| 00:00:01 |
|   1 |  PX COORDINATOR              |           |       |       |            |          |
|   2 |   PX SEND QC (RANDOM)        | :TQ10000  |    10 |   230 |  6208   (7)| 00:00:01 |
|   3 |    PX BLOCK ITERATOR         |           |    10 |   230 |  6208   (7)| 00:00:01 |
|*  4 |     TABLE ACCESS STORAGE FULL| BOWIE_ONE |    10 |   230 |  6208   (7)| 00:00:01 |
------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):

---------------------------------------------------

4 - storage("CODE"=42)
    filter("CODE"=42)

Statistics
----------------------------------------------------------

   12  recursive calls
    0  db block gets
39000  consistent gets
    0  physical reads
  132  redo size
  867  bytes sent via SQL*Net to client
  588  bytes received via SQL*Net from client
    2  SQL*Net roundtrips to/from client
    0  sorts (memory)
    0  sorts (disk)
   10  rows processed

The following Automatic Indexing report detailed the following:

SQL> select dbms_auto_index.report_last_activity() report from dual;

REPORT
--------------------------------------------------------------------------------
GENERAL INFORMATION
-------------------------------------------------------------------------------
Activity start               : 26-JUN-2019 13:03:30
Activity end                 : 26-JUN-2019 21:13:06
Executions completed         : 24
Executions interrupted       : 0
Executions with fatal error  : 0
-------------------------------------------------------------------------------
SUMMARY (AUTO INDEXES)
-------------------------------------------------------------------------------
Index candidates                             : 1
Indexes created (visible / invisible)        : 1 (1 / 0)
Space used (visible / invisible)             : 184.55 MB (184.55 MB / 0 B)
Indexes dropped                              : 0
SQL statements verified                      : 3
SQL statements improved (improvement factor) : 1 (19500x)
SQL plan baselines created                   : 0
Overall improvement factor                   : 6.9x
-------------------------------------------------------------------------------
SUMMARY (MANUAL INDEXES)
-------------------------------------------------------------------------------

Unused indexes    : 0
Space used        : 0 B
Unusable indexes  : 0

So an index was indeed created. Later in the report:

INDEX DETAILS

-------------------------------------------------------------------------------
The following indexes were created:
-------------------------------------------------------------------------

-------------------------------------------------------------------------
| Owner | Table     | Index                | Key  | Type   | Properties |
-------------------------------------------------------------------------
| BOWIE | BOWIE_ONE | SYS_AI_5tabfu6wtkbdh | CODE | B-TREE | NONE       |
-------------------------------------------------------------------------
-------------------------------------------------------------------------------

VERIFICATION DETAILS

-------------------------------------------------------------------------------The performance of the following statements improved:
-------------------------------------------------------------------------------

Parsing Schema Name  : BOWIE
SQL ID               : 9n89axkwrvw4b
SQL Text             : select * from bowie_one where code=42
Improvement Factor   : 19500x

Execution Statistics:
-----------------------------

                    Original Plan                 Auto Index Plan
                    ----------------------------  ----------------------------
Elapsed Time (s):   198342                        961
CPU Time (s):       187768                        1112
Buffer Gets:        39000                         13
Optimizer Cost:     6208                          14
Disk Reads:         0                             2
Direct Writes:      0                             0
Rows Processed:     10                            10
Executions:         1                             1

So the above details that an index on the CODE column of the BOWIE_ONE table was indeed created after just 1 execution.

For those wondering, yes the Elaspsed and CPU times are actually in Microseconds (1 millionth of a second) and not in seconds as stated…

The final section of the report details:

PLANS SECTION
---------------------------------------------------------------------------------------------
- Original
-----------------------------

Plan Hash Value  : 227986582
------------------------------------------------------------------------------------
| Id | Operation                      | Name      | Rows | Bytes | Cost | Time     |
------------------------------------------------------------------------------------
|  0 | SELECT STATEMENT               |           |      |       | 6208 |          |
|  1 |  PX COORDINATOR                |           |      |       |      |          |
|  2 |    PX SEND QC (RANDOM)         | :TQ10000  |   10 |   230 | 6208 | 00:00:01 |
|  3 |     PX BLOCK ITERATOR          |           |   10 |   230 | 6208 | 00:00:01 |
|  4 |      TABLE ACCESS STORAGE FULL | BOWIE_ONE |   10 |   230 | 6208 | 00:00:01 |
------------------------------------------------------------------------------------

Notes
-----

- dop_op_reason = scan of object BOWIE.BOWIE_ONE
- dop = 2
- px_in_memory_imc = no
- px_in_memory = no
- With Auto Indexes
-----------------------------

Plan Hash Value  : 2734060610
-------------------------------------------------------------------------------------------------------
| Id  | Operation                             | Name                 | Rows | Bytes | Cost | Time     |
-------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                      |                      |  10   |  230 |   14 | 00:00:01 |
|   1 |   TABLE ACCESS BY INDEX ROWID BATCHED | BOWIE_ONE            |  10   |  230 |   14 | 00:00:01 |
| * 2 |    INDEX RANGE SCAN                   | SYS_AI_5tabfu6wtkbdh |  10   |      |    3 | 00:00:01 |
-------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
------------------------------------------

* 2 - access("CODE"=42)

Notes
-----

- Dynamic sampling used for this statement ( level = 11 )

It details that indeed, a new plan using the newly Automatic Index would  be substantially more efficient.

If we look at details of the new Automatic Index:

SQL> select index_name, auto, constraint_index, visibility, compression, status, num_rows, leaf_blocks, clustering_factor  from user_indexes where table_name='BOWIE_ONE';

INDEX_NAME             AUT CON VISIBILIT COMPRESSION   STATUS     NUM_ROWS LEAF_BLOCKS CLUSTERING_FACTOR
---------------------- --- --- --------- ------------- -------- ---------- ----------- -----------------
BOWIE_ONE_PK           NO  YES VISIBLE   DISABLED      VALID      10000000       19642             57523
SYS_AI_5tabfu6wtkbdh   YES NO  VISIBLE   DISABLED      VALID      10000000       22285          10000000

SQL> select index_name, column_name, column_position
from user_ind_columns where table_name='BOWIE_ONE' order by index_name, column_position;

INDEX_NAME             COLUMN_NAME     COLUMN_POSITION
---------------------- --------------- ---------------
BOWIE_ONE_PK           ID                            1
SYS_AI_5tabfu6wtkbdh   CODE                          1

The newly created Automatic Index is both Valid and Visible and so can be used globally within the database.

If I now re-run the original query:

SQL> select * from bowie_one where code=42;

10 rows selected.

Execution Plan
--------------------------------------------------------------------------------------------------------------
| Id  | Operation                             | Name                 | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                      |                      |    10 |   230 |    13   (0)| 00:00:01 |
|   1 |  PX COORDINATOR                       |                      |       |       |            |          |
|   2 |   PX SEND QC (RANDOM)                 | :TQ10001             |    10 |   230 |    13   (0)| 00:00:01 |
|   3 |    TABLE ACCESS BY INDEX ROWID BATCHED| BOWIE_ONE            |    10 |   230 |    13   (0)| 00:00:01 |
|   4 |     BUFFER SORT                       |                      |       |       |            |          |
|   5 |      PX RECEIVE                       |                      |    10 |       |     3   (0)| 00:00:01 |
|   6 |       PX SEND HASH (BLOCK ADDRESS)    | :TQ10000             |    10 |       |     3   (0)| 00:00:01 |
|   7 |        PX SELECTOR                    |                      |       |       |            |          |
|*  8 |           INDEX RANGE SCAN            | SYS_AI_5tabfu6wtkbdh |    10 |       |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

8 - access("CODE"=42)

Statistics
---------------------------------------------------------

 12  recursive calls
  0  db block gets
 13  consistent gets
  0  physical reads
  0  redo size
867  bytes sent via SQL*Net to client
588  bytes received via SQL*Net from client
  2  SQL*Net roundtrips to/from client
  2  sorts (memory)
  0  sorts (disk)
 10  rows processed

The CBO now uses the newly created Automatic Index.

So it only potentially takes just the one execution of an SQL statement for an Automatic Index to be created.

Therefore some caution needs to be exercised in environments where there may be a very large number of ad-hoc queries where specific indexes may not be necessary for once only executed predicate combinations.

That said, the Automatic Indexing process is highly efficient in building only the bare minimum of column indexed combinations to cater for all known SQL predicates.

More on this in a future post.

Speaking at Trivadis Performance Days 2019 August 28, 2019

Posted by Richard Foote in Oracle Indexes, Performance Days 2019.
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performance days

I’ll again be speaking at the wonderful Trivadis Performance Days 2019 conference in Zurich, Switzerland on 26-27 September.

There’s again another fantastic lineup of speakers, including:

  • CHRISTIAN ANTOGNINI
  • IVICA ARSOV
  • MARK ASHDOWN
  • SHASANK CHAVAN
  • EMILIANO FUSAGLIA
  • STEPHAN K√ĖHLER
  • JONATHAN LEWIS
  • FRANCK PACHOT
  • TANEL PODER
  • DANI SCHNIDER

 

I’ll be presenting two papers:

  • Oracle 18c and Oracle 19c New Indexing Features
  • Improving Performance with Indexing and Partitioning

 

For all the details, including the agenda and how to register: https://m.trivadis.com/performance-days-en

I can’t recommend this conference enough, one that focuses and specialises on improving performance in Oracle Database environments.

Oh, and the beer served is excellent as well.

 

performance days beers

 

Speaking at Oracle OpenWorld 2019 August 22, 2019

Posted by Richard Foote in OOW19, Oracle Indexes.
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OOW Speaking

It’s been remarkably 9 years since I’ve been to Oracle OpenWorld, but will finally get the opportunity to present there again this year (with many thanks to the Oracle ACE Director program for making this possible).

Details of my presentation are as follows:

Conference: Oracle OpenWorld

Session Type: Conference Session

Session ID: CON1432

Session Title: Oracle Database 19c: In-Depth Look into the New Automatic Indexing Feature

Room: Moscone South – Room 152A

Date: 09/17/19

Start Time: 11:15:00 AM

End Time: 12:00:00 PM

I promise it to be a fast-paced, content rich, action-packed presentation that will leave you much wiser about the cool capabilities of Oracle Database 19c Automatic Indexing.

The current allocated room is almost full with pre-registrations so if you’re interested in learning how Oracle’s new Automatic Indexing feature works, I recommend registering for the session ASAP (or to keep following my blog).

I’m really looking forward to catching with many of my Oracle friends again, so please do stop by to say hi if you see me loitering around ūüôā

 

For the record, I’ve hardly changed a bit in the intervening last 9 years ūüôā

oow-day-2-006

AUSOUG Connect 2019 Conference Series August 21, 2019

Posted by Richard Foote in AUSOUG, Connect 2019, Oracle Indexes.
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Connect 2019

 

AUSOUG will again be running their excellent CONNECT 2019 conference series this year at the following great venues:

  • Monday 14th October ‚Äď Rendezvous Hotel In Melbourne
  • Wednesday 16th October ‚Äst Mercure Hotel in Perth

As usual, there’s a wonderful lineup of speakers from both Australia and overseas including:

  • Connor McDonald
  • Scott Wesley
  • Guy Harrison
  • Jeffrey Kemp
  • Francisco Munoz Alvarez
  • Gavin Soorma
  • Douglas Hood
  • Charles Kim
  • Craig Shallahamer
  • David Peake
  • Patrick Barel
  • Christopher Jones

to name but a few. You can see the full list of speakers here.

I’ll will also be presenting my fully updated and revised “10 Things You Might Not Know About Oracle Indexes But Really Should” presentation, that covers the more important and recent indexing capabilities that are not so widely known or understood but can be critical for optimal database/application performance.

If you’re an Oracle professional based in Australia, this is definitely the Oracle conference for you. Hopefully, I’ll get to meet many of you at either Melbourne or Perth ūüôā

For more information, including how to register, visit the Connect 2019 site here.

 

ausoug pic

Oracle 19c Automatic Indexing: My First Auto Index (Absolute Beginners) August 19, 2019

Posted by Richard Foote in 19c, 19c New Features, Automatic Indexing, Oracle Indexes.
3 comments

absolute beginners

I am SOOOO struggling with this nightmare block editor but here goes. Please excuse any formatting issues below:

I thought it was time to show the new Oracle 19c Automatic Indexing feature in action and what better way than to go through how I created my first ever Automatic Index.

To start, I create a typically simple little table:

SQL> create table bowie (id number constraint bowie_pk primary key, code number, name varchar2(42));

Table created.

SQL> insert into bowie select rownum, mod(rownum, 1000000)+1, 'David Bowie' from dual connect by level  commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats(ownname=>null, tabname=>'BOWIE');

PL/SQL procedure successfully completed.

SQL> select index_name, auto, constraint_index, visibility, compression, status, num_rows, leaf_blocks, clustering_factor from user_indexes where table_name='BOWIE';

INDEX_NAME                  AUT CON VISIBILIT COMPRESSION   STATUS     NUM_ROWS LEAF_BLOCKS CLUSTERING_FACTOR
------------------------- --- --- --------- ------------- -------- ---------- ----------- -----------------
BOWIE_PK                    NO  YES VISIBLE   DISABLED        VALID      10000000         19429               58133

The key column here is CODE, which is highly selective with just 10 rows on average per CODE value.

If I run the following query a number of times:

SQL> select * from bowie where code=42;

10 rows selected.

Execution Plan

--------------------------------------------------------------------------------------------
| Id  | Operation                      | Name     | Rows    | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT               |          |      10 |   230 |  6208   (7)| 00:00:01 |
|   1 |  PX COORDINATOR                |          |         |       |            |          |
|   2 |   PX SEND QC (RANDOM)          | :TQ10000 |      10 |   230 |  6208   (7)| 00:00:01 |
|   3 |    PX BLOCK ITERATOR           |          |      10 |   230 |  6208   (7)| 00:00:01 |
|*  4 |     TABLE ACCESS STORAGE FULL  | BOWIE    |      10 |   230 |  6208   (7)| 00:00:01 |
---------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

4 - storage("CODE"=42)
filter("CODE"=42)

Statistics
----------------------------------------------------------
    6  recursive calls
    0  db block gets
39026  consistent gets
    0  physical reads
    0  redo size
  867  bytes sent via SQL*Net to client
  588  bytes received via SQL*Net from client
    2  SQL*Net roundtrips to/from client
    0  sorts (memory)
    0  sorts (disk)
   10  rows processed

The query runs slowly as it performs a Full Table Scan of a 10M row table when returning just 10 runs.

Perhaps an index would be a good idea…

With Auto Indexing, we just wait approx. 15 minutes until the Auto Index task completes, or manually run exec dbms_auto_index_internal.task_proc(true);

As discussed in my previous blog post, the Auto Indexing task will look at the workload over the past 15 minutes and determine if a new index might be warranted to improve the performance of an SQL.

We can query the results of the last Auto Index task by running the following:

SQL> select dbms_auto_index.report_last_activity() report from dual;

REPORT
--------------------------------------------------------------------------------
GENERAL INFORMATION
-------------------------------------------------------------------------------
Activity start                  : 20-JUN-2019 08:12:15
Activity end                    : 20-JUN-2019 08:12:55
Executions completed            : 1
Executions interrupted          : 0
Executions with fatal error     : 0
-------------------------------------------------------------------------------
SUMMARY (AUTO INDEXES)
-------------------------------------------------------------------------------
Index candidates                                : 1
Indexes created (visible / invisible)           : 1 (1 / 0)
Space used (visible / invisible)                : 184.55 MB (184.55 MB / 0 B)
Indexes dropped                                 : 0
SQL statements verified                         : 2
SQL statements improved (improvement factor)    : 1 (39044.8x)
SQL plan baselines created                      : 0
Overall improvement factor                      : 6.9x
-------------------------------------------------------------------------------

SUMMARY (MANUAL INDEXES)
-------------------------------------------------------------------------------

Unused indexes    : 0
Space used        : 0 B
Unusable indexes  : 0

At this point in the report, we can see Oracle has verified 2 SQL statements and has created 1 new, visible index using 184.55 MB of space. It has improved 1 SQL statement by a factor of 39044.8x and improved things overall by a factor of 6.9x. (we’ll look at how Oracle determines these values in a later post).

The report continues with the Index Details section:

INDEX DETAILS

-------------------------------------------------------------------------------
The following indexes were created:
---------------------------------------------------------------------
| Owner | Table | Index                | Key  | Type   | Properties |
---------------------------------------------------------------------
| BOWIE | BOWIE | SYS_AI_600vgjmtqsgv3 | CODE | B-TREE | NONE       |
---------------------------------------------------------------------

Oracle has decided to create a new indexed called “SYS_AI_600vgjmtqsgv3” on the CODE column of the BOWIE table. Notice the mixed case naming convention for the new Auto Index, oh what fun and games to be had…

Next the Verification Details section:

VERIFICATION DETAILS

-------------------------------------------------------------------------------
The performance of the following statements improved:
-------------------------------------------------------------------------------

Parsing Schema Name  : BOWIE

SQL ID               : dd5gzx7skf6as
SQL Text             : select * from bowie where code=42
Improvement Factor   : 39044.8x

Execution Statistics:
-----------------------------

                     Original Plan                 Auto Index Plan
                     ----------------------------  ----------------------------

Elapsed Time (s):    3241698                       108
CPU Time (s):        3174021                       108
Buffer Gets:         663764                        13
Optimizer Cost:      6204                          14
Disk Reads:          0                             0
Direct Writes:       0                             0
Rows Processed:      170                           10
Executions:          17                            1

So the SQL we previously ran has an improvement factor of 39044.8x with the new plan that uses the newly created Auto Index. These numbers are a little nonsensical as we’ll see in a later post, but it does sound kinda impressive…

Finally, we get to the Plans Section of the report:

PLANS SECTION
---------------------------------------------------------------------------------------------
- Original
-----------------------------

Plan Hash Value  : 3567883234
-------------------------------------------------------------------------------------
| Id | Operation                      | Name     | Rows   | Bytes | Cost | Time     |
-------------------------------------------------------------------------------------
|  0 | SELECT STATEMENT               |          |        |       | 6204 |          |
|  1 |  PX COORDINATOR                |          |        |       |      |          |
|  2 |    PX SEND QC (RANDOM)         | :TQ10000 |    425 | 20825 | 6204 | 00:00:01 |
|  3 |     PX BLOCK ITERATOR          |          |    425 | 20825 | 6204 | 00:00:01 |
|  4 |      TABLE ACCESS STORAGE FULL | BOWIE    |    425 | 20825 | 6204 | 00:00:01 |
-------------------------------------------------------------------------------------

- With Auto Indexes

-----------------------------
Plan Hash Value  : 493118340

-------------------------------------------------------------------------------------------------------
| Id  | Operation                             | Name                 | Rows | Bytes | Cost | Time     |
-------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                      |                      |   10 |   230 |   14 | 00:00:01 |
|   1 |   TABLE ACCESS BY INDEX ROWID BATCHED | BOWIE                |   10 |   230 |   14 | 00:00:01 |
| * 2 |    INDEX RANGE SCAN                   | SYS_AI_600vgjmtqsgv3 |   10 |       |    3 | 00:00:01 |

Here Oracle compares the original plan with the new plan that uses the new index. The new plan is much more efficient and so the index is created as a Valid, Visible index.

Note: the vast majority of my test cases were run on the Dedicated Autonomous Application Transaction Processing (ATP) environment, where parallelism is common for most plans by default.

Let’s look at details of the newly created Automatic Index:

 

SQL> select index_name, auto, constraint_index, visibility, compression, status, num_rows, leaf_blocks, clustering_factor  from user_indexes where table_name='BOWIE';

INDEX_NAME                AUT CON VISIBILIT COMPRESSION   STATUS     NUM_ROWS LEAF_BLOCKS CLUSTERING_FACTOR
------------------------- --- --- --------- ------------- -------- ---------- ----------- -----------------
BOWIE_PK                  NO  YES VISIBLE   DISABLED      VALID      10000000       19429             58133
SYS_AI_600vgjmtqsgv3      YES NO  VISIBLE   DISABLED      VALID      10000000       22419          10000000

SQL> select index_name, column_name, column_position from user_ind_columns where table_name='BOWIE' order by index_name, column_position;

INDEX_NAME                COLUMN_NAME          COLUMN_POSITION
------------------------- -------------------- ---------------
BOWIE_PK                  ID                                 1
SYS_AI_600vgjmtqsgv3      CODE                               1

 

There is new column column called AUTO in DBA_INDEXES to denote where an index has been automatically created by Oracle.

So the new SYS_AI_600vgjmtqsgv3 Automatic Index on the CODE column is both VISIBLE and VALID¬†in this case,¬† meaning it can be globally used within the database. As we’ll see if future posts, this is not always the case with Automatic Indexes.

If we now re-run the initial SQL query I ran and look at the execution plan:

 

SQL> select * from bowie where code=42;

10 rows selected.

Execution Plan
--------------------------------------------------------------------------------------------------------------
| Id  | Operation                             | Name                 | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                      |                      |    10 |   230 |    13   (0)| 00:00:01 |
|   1 |  PX COORDINATOR                       |                      |       |       |            |          |
|   2 |   PX SEND QC (RANDOM)                 | :TQ10001             |    10 |   230 |    13   (0)| 00:00:01 |
|   3 |    TABLE ACCESS BY INDEX ROWID BATCHED| BOWIE                |    10 |   230 |    13   (0)| 00:00:01 |
|   4 |     BUFFER SORT                       |                      |       |       |            |          |
|   5 |      PX RECEIVE                       |                      |    10 |       |     3   (0)| 00:00:01 |
|   6 |       PX SEND HASH (BLOCK ADDRESS)    | :TQ10000             |    10 |       |     3   (0)| 00:00:01 |
|   7 |        PX SELECTOR                    |                      |       |       |            |          |
|*  8 |           INDEX RANGE SCAN            | SYS_AI_600vgjmtqsgv3      10         |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

8 - access("CODE"=42)

Statistics
----------------------------------------------------------
 12  recursive calls
  0  db block gets
 13  consistent gets
  0  physical reads
  0  redo size
867  bytes sent via SQL*Net to client
588  bytes received via SQL*Net from client
  2  SQL*Net roundtrips to/from client
  2  sorts (memory)
  0  sorts (disk)
 10  rows processed

 

We notice the new Automatic Index has been used by the CBO to substantially improve the performance of the query (just 13 consistent gets).

OK, so that’s the end of the Intro. In the next blog article, we’ll start looking at some of the specifics of how Auto Indexing works behind the covers and why it’s important to understand some of these workings…

2019 Public Appearances (What In The World) August 15, 2019

Posted by Richard Foote in Oracle Indexes.
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I’ll be presenting at a number of Oracle events over the remainder of the year. Details as follows:

Oracle Open World – San Francisco (16-19 September 2019)

  • Session Type: Conference
  • Session Session ID: CON1432
  • Session Title: Oracle Database 19c: In-Depth Look into the New Automatic Indexing Feature
  • Room: Moscone South – Room 152A Date: 09/17/19
  • Start Time: 11:15:00 AM
  • End Time: 12:00:00 PM

Link: https://events.rainfocus.com/widget/oracle/oow19/catalogow19?

Trivadis Performance Days 2019 (26-27 September 2019)

I have the following 2 presentations:

  • Indexing With Partitioning
  • Oracle Database 18c and 19c New Indexing Related Features

Link: https://www.trivadis.com/en/training/performance-days-2019-tvdpdays

AUSOUG Connect 2019 Series (Melbourne 14 October, Perth 16 October)

I have the following presentation:

  • 10 Things You Might Not Know But Really Should About Oracle Indexes

Link: https://www.ausoug.org.au/whats-on/connect2019/

ANZ Let’s Talk Database Series

I have the following 2 presentations:

  • Oracle Database 19c New Features
  • Oracle Exadata X8 New Features

Following are the confirmed dates:

  • Canberra: 22 October 2019
  • Sydney: 23 October 2019
  • Melbourne: 24 October 2019
  • Brisbane: 29 October 2019
  • Auckland: 30 October 2019
  • Wellington: 31 October 2019

Registration links coming soon.

UKOUG Techfest19 Brighton, UK (1-4 December 2019)

I have the following 3 presentations:

  • Oracle Database 19c New Features (Tuesday, 3 December 11:00-11:45am)
  • Oracle Indexing Q&A with Richard Foote (Tuesday, 3 December 2:45-3:30pm)
  • 10 Things You Might Not Know But Really Should About Oracle Indexes (Wednesday, 2:45-3:30pm)

Link: https://ukoug.org/page/techfest19

Hopefully I can catch you at one of these events. Don’t be shy, please say hi ūüôā

Announcement: “Oracle Performance Diagnostics and Tuning” Webinar – 20-23 August 2019. July 30, 2019

Posted by Richard Foote in Oracle Performance Diagnostics and Tuning Webinar.
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seminar photo

I have just scheduled a new “Oracle Performance Diagnostics and Tuning” webinar to run between 20-23 August 2019, specifically for my friends in New Zealand, but is open to anyone.

It will run between 7am-11am AEST each day, which is perfect for those in NZ, but also other parts of the world such as Western USA.

This is a must attend webinar aimed at Oracle professionals (both DBAs and Developers) who are interested in Performance Tuning. It details how to maximise the performance of both Oracle databases and associated applications and how to diagnose and address any performance issues as quickly and effectively as possible.

A unique feature of this training is that you can submit YOUR AWR reports and using the tuning methodology and techniques discussed in the webinar can be applied directly to determining and addressing performance issues with YOUR own databases.

For all webinar content and how to register, please visit: https://richardfooteconsulting.com/performance-tuning-seminar/

As always, places are strictly limited and can be purchased below:

Webinar Series 20-23 August 2019 (start 7am AEST, end 11am AEST): Buy Now Button

If you have any questions at all, please contact me at richard@richardfooteconsulting.com

Oracle 19c Automatic Indexing: Configuration (All I Need) July 29, 2019

Posted by Richard Foote in Automatic Indexing, AUTO_INDEX_COMPRESSION, AUTO_INDEX_DEFAULT_TABLESPACE, AUTO_INDEX_MODE, AUTO_INDEX_REPORT_RETENTION, AUTO_INDEX_RETENTION_FOR_AUTO, AUTO_INDEX_RETENTION_FOR_MANUAL, AUTO_INDEX_SCHEMA, AUTO_INDEX_SPACE_BUDGET, DBA_AUTO_INDEX_CONFIG, DBMS_AUTO_INDEX.CONFIGURE, Oracle Indexes, Oracle19c, SMB$CONFIG.
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In Rainbows

In this post, I’ll discuss how to configure the new Automatic Indexing capability introduced in Oracle Database 19c.

The intent of Oracle here is to make the configuration of Automatic Indexing as simplistic as possible, with as few levers for DBAs to potentially stuff up as possible. The ultimate goal would be to have a switch that just turns the feature on and that all necessary indexes then simply be created/modified/dropped as required. It’s not quite there yet, but it’ll no doubt get closer with each new release.

By default, Automatic Indexing is turned OFF. To turn on these capabilities, you simply run the following using the DBMS_AUTO_INDEX.CONFIGURE procedure:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_MODE‘,’IMPLEMENT‘);

PL/SQL procedure successfully completed.

That’s it. Automatic Indexing is now enabled and as discussed in the previous blog post on the Automatic Indexing Methodology, every 15 minutes, the SYS_AUTO_INDEX_TASK background task will kickoff and automatically create/replace/drop any database indexes as necessary.

Another option, is to enable Automatic Indexing in ‘REPORT ONLY‘ mode:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_MODE’,’REPORT ONLY‘);

PL/SQL procedure successfully completed.

This will only create new indexes as INVISIBLE indexes, which are not considered by default by the CBO. The intent here is that the DBA can investigate the newly created Automatic Indexes and decide whether turning on this feature for real would be a good idea. Need to exercise some caution with this option though, as the limited options regarding how to subsequently administer the created Invisible Automatic Indexing can be problematic. I’ll discuss all this is more detail in a future post.

To turn off Automatic Indexing, simply set the AUTO_INDEX_MODE to ‘OFF’:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_MODE’,’OFF‘);

PL/SQL procedure successfully completed.

Note here the documentation states “the existing auto indexes are disabled” which is incorrect. New Automatic Indexes will no longer be created, but existing Automatic Indexes will still be both Visible and Valid and available to the CBO for continued use.

By default, Automatic Indexing considers all tables in all “user created” schemas. However, this can be controlled with the AUTO_INDEX_SCHEMA option within the DBMS_AUTO_INDEX.CONFIGURE procedure. You can control which schemas to either explicitly include or exclude from Automatic Indexing considerations.

To add the BOWIE schema to an “Inclusion” list of schemas, you run the following:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_SCHEMA‘,’BOWIE’,¬†TRUE);

PL/SQL procedure successfully completed.

 

To add the BOWIE schema to an “Exclusion” list of schemas, you run the following:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_SCHEMA‘,’BOWIE’,¬†FALSE);

PL/SQL procedure successfully completed.

 

To remove the BOWIE schema from whichever list it belongs, you run the following:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_SCHEMA‘, ‘BOWIE’, NULL);

PL/SQL procedure successfully completed.

 

To remove all schemas from the “Inclusion” list, you run the following:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_SCHEMA‘, NULL, TRUE);

PL/SQL procedure successfully completed.

 

You can configure a tablespace to be the tablespace in which all Automatic Indexes are to now be created by running the following:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_DEFAULT_TABLESPACE‘,’INDEX_TS’);

PL/SQL procedure successfully completed

The INDEX_TS tablespace is now the location of all newly created Automatic Indexes.

You can also control how much of the configured Automatic Indexing tablespace is to be reserved for use by Automatic Indexes (default 50%) by running the following:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_SPACE_BUDGET‘, ’42’);

PL/SQL procedure successfully completed.

Now, only 42% of the INDEX_TS tablespace can be used by Automatic Indexes.

 

You can control the number of days (the default is 373 days) in which if an Automatic Index has been deemed NOT to have been used, it will be automatically dropped. The following command:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_RETENTION_FOR_AUTO‘, ’42’);

PL/SQL procedure successfully completed.

will automatically drop any Automatic Index that is deemed not to have been used in the last 42 days.

Note: Oracle uses the new Indexing Tracking feature introduced in Oracle 12.2 to determine if an index has/has not been used, which has limitations that could potentially result in an Automatic Index that has been “lightly” used during the retention period being dropped. This will be discussed in more detail in a future post.

A similar retention configuration can be implemented for manually created indexes. The following command:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_RETENTION_FOR_MANUAL’,’42’);

PL/SQL procedure successfully completed.

will automatically drop any manually created index that is deemed not to have been used in the last 42 days.

Note: the same Indexing Tracking limitations means that manually created indexes lightly used during the last 42 days could also be automatically dropped.

I will discuss various undocumented implications of automatically dropping both Automatic and Manual Indexes in future posts.

 

Very importantly,  the Automatic Indexing logs on which Automatic Indexing Reports are based are only retained by default for just 31 days. To change the time before the Automatic Indexing logs are deleted, you run the following:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_REPORT_RETENTION‘,’342’);

PL/SQL procedure successfully completed.

The Automatic Indexing logs are now retained for 342 days. These Automatic Indexing reports (and hence logs) are critical for understanding what the Automatic Indexing featuring is doing within the database and will be discussed extensively in future posts. I would recommend increasing the retention period from the 31 days default.

 

The final configuration option is not officially documented (yet) and controls whether or not Advanced Compression is used for Automatic Indexes. The default is that Advanced Compression is disabled, but this can be changed as follows:

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_COMPRESSION‘,’ON’);

PL/SQL procedure successfully completed.

All Automatic Indexes are now automatically compressed using Advanced Low Compression.

I believe this was at some stage going to be the default behaviour, but due to licencing considerations and that many sites don’t have the Advanced Compression Option, this was subsequently changed. If you do have Advanced Compression, I would strongly recommend turning this ON, as implementing Advanced Low Compression is a relatively no-brainer beneficial decision.

I will however discuss the various undocumented implications of Advanced Compression in relation to Automatic Indexing in future posts.

The documented DBA_AUTO_INDEX_CONFIG view can be used to view the current setting for all of these configuration options:

SQL> select * from dba_auto_index_config;

PARAMETER_NAME                             PARAMETER_VALUE      LAST_MODIFIED                              MODIFIED_BY
---------------------------------------- -------------------- ---------------------------------------- --------------------
AUTO_INDEX_COMPRESSION                   OFF
AUTO_INDEX_DEFAULT_TABLESPACE
AUTO_INDEX_MODE                          REPORT ONLY           03-JUL-19 05.43.28.000000 AM            BOWIE
AUTO_INDEX_REPORT_RETENTION              31
AUTO_INDEX_RETENTION_FOR_AUTO            42                    20-JUN-19 06.32.06.000000 AM            BOWIE
AUTO_INDEX_RETENTION_FOR_MANUAL                                02-JUL-19 12.12.21.000000 AM            BOWIE
AUTO_INDEX_SCHEMA  schema IN (BOWIE)                           20-JUN-19 06.27.26.000000 AM            BOWIE
AUTO_INDEX_SPACE_BUDGET                  50

 

Additionally, you can view both the documented and undocumented settings regarding Automatic Indexing by looking at the SMB$CONFIG table:

 

SQL> select parameter_name, parameter_value
from sys.SMB$CONFIG;

PARAMETER_NAME                           PARAMETER_VALUE
---------------------------------------- ---------------
SPACE_BUDGET_PERCENT                                  10
PLAN_RETENTION_WEEKS                                  53
SPM_TRACING                                            0
AUTO_CAPTURE_PARSING_SCHEMA_NAME                       0
AUTO_CAPTURE_MODULE                                    0
AUTO_CAPTURE_ACTION                                    0
AUTO_CAPTURE_SQL_TEXT                                  0
AUTO_INDEX_SCHEMA                                      0
AUTO_INDEX_DEFAULT_TABLESPACE                          0
AUTO_INDEX_SPACE_BUDGET                               50
AUTO_INDEX_REPORT_RETENTION                           31
AUTO_INDEX_RETENTION_FOR_AUTO                          0
AUTO_INDEX_RETENTION_FOR_MANUAL                        0
AUTO_INDEX_MODE                                        0
_AUTO_INDEX_TRACE                                      0
_AUTO_INDEX_TASK_INTERVAL                            900
_AUTO_INDEX_TASK_MAX_RUNTIME                        3600
_AUTO_INDEX_IMPROVEMENT_THRESHOLD                     20
_AUTO_INDEX_REGRESSION_THRESHOLD                      10
_AUTO_INDEX_ABSDIFF_THRESHOLD                        100
_AUTO_INDEX_STS_CAPTURE_TASK                           0
_AUTO_INDEX_CONTROL                                    0
_AUTO_INDEX_DERIVE_STATISTICS                          0
_AUTO_INDEX_CONCURRENCY                                1
_AUTO_INDEX_SPA_CONCURRENCY                            1
_AUTO_INDEX_REBUILD_TIME_LIMIT                        30
_AUTO_INDEX_REBUILD_COUNT_LIMIT                        5
_AUTO_INDEX_REVERIFY_TIME                             30
AUTO_INDEX_COMPRESSION                                 0
AUTO_SPM_EVOLVE_TASK                                   0
AUTO_SPM_EVOLVE_TASK_INTERVAL                       3600
AUTO_SPM_EVOLVE_TASK_MAX_RUNTIME                    1800

 

I’ll discuss a number of these undocumented configuration options in future posts.

In my next post however, we’ll look at the Automatic Indexing feature in action with a very simple example to start with…

Oracle 19c Automatic Indexing: Methodology Introduction (After Today) July 24, 2019

Posted by Richard Foote in Automatic Indexing, Oracle Indexes, Oracle19c.
1 comment so far

young americans

For the past month or so I’ve been playing around extensively with the new Oracle 19c “Automatic Indexing” feature, so I thought it was time to start blogging about it.

Considering it’s only in “Version 1” status, my initial impression is very positive in that it works extremely well doing at what it’s initially designed to do. There are certainly “interesting” bits of behavior here and there and some missing functionality, but it’s a whole lot better than DB running sub-optimally due to missing indexes.

This post is purely an introduction in which I’ll just discuss the general methodology behind the Automatic Indexing (AI) capability, initially in a somewhat simplistic manner in order to convey the more important concepts. I’ll expand and discuss many of the actual complexities behind this cool feature in future posts.

The basic concept behind AI is that the DBA via a simple “switch” can turn on the AI¬† feature and have the Oracle Database automatically create/drop/modify any necessary database indexes as required.

The Oracle database continually captures SQL workloads and keeps track of any new column usages within SQL predicates (as well as associated plans and execution statistics) that might warrant the need for a new index. Note that currently, only equality predicates are considered when determining potential candidate Automatic Indexes.

By default, a background task is executed every 15 minutes that by default runs for up to an hour, to determine if the database can identify any new indexes that “might” be warranted. There are a number of reasons why the tasks might actually take considerably more time than the default 1 hour (I’ll expand on reasons why in future posts).

Candidate indexes that have been detected based on the previous 15 mins database workload are initially created as INVISIBLE/UNUSABLE indexes and hard parsed with the captured SQLs to determine if the index could be considered by the CBO.

If the candidate indexes are indeed viable, the indexes are then created as INVISIBLE/USABLE indexes and verified via the SQL Performance Analyzer using SQL Tuning Sets to determine if the performance of the captured SQLs have indeed improved from the existing plans when using the newly created Automatic Indexes.

If performance actually improves for all captured SQLs using a new Automatic Index, the Automatic Index is made VISIBLE and is now available for general database use. If performance is worse for all captured SQLs, the Automatic Index is made UNUSABLE again and hence not available to the CBO. If performance is better for some SQLs but worse for others, well the story gets a little complicated. In “theory”, the Automatic Index is made USABLE but SQL baselines are created for the SQLs that suffer performance degradation to not use the Automatic Index. Any such SQLs are effectively “blacklisted” and are not (easily) considered for future “new” AI deliberations.¬† As I’ll discuss in future posts, things are not actually quite as straightforward as that.

So depending on the scenario, Automatic Indexes can end up being in any of the following states:

  • Invisible and Unusable
  • Invisible and Valid
  • Visible and Unusable
  • Visible and Valid

When Visible and Valid, Automatic Indexes can ultimately be:

  • Used by the CBO
  • Not used by the CBO (even by the SQL that caused its creation)

As part of the identify candidate index process, Oracle will consider if a new index can be logically “merged” with an existing index and effectively replace an existing index by dropping and replacing it with a new Automatic Index.

AI will also monitor if existing (either Automatic or Manual) indexes are not currently being used within the database. If after a configurable period of time an index is deemed not to have been used within that time, the index will be automatically dropped during the AI 15 minute task.

This is the basic AI story. The actual story is a tad more complicated and which I’ll expand upon in many many future posts, so keep your questions until then ūüôā

 

Importantly, AI is ONLY available on the Exadata platform or on Oracle Cloud environments. It is NOT available on standard On-Premises Oracle 19c deployments. Attempts to turn the feature on where not supported will only result in disappointment:

 

SQL> EXEC DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_MODE’,’IMPLEMENT’);
BEGIN DBMS_AUTO_INDEX.CONFIGURE(‘AUTO_INDEX_MODE’,’IMPLEMENT’); END;

*
ERROR at line 1:
ORA-40216: feature not supported
ORA-06512: at “SYS.DBMS_SYS_ERROR”, line 79
ORA-06512: at “SYS.DBMS_AUTO_INDEX_INTERNAL”, line 9180
ORA-06512: at “SYS.DBMS_AUTO_INDEX”, line 283
ORA-06512: at line 1

 

I’ll next discuss the AI configuration options available to the DBA…