safe harbor statement · the oracle optimizer in oracle database 12c 12c optimizer column usage...

Copyright © 2018, Oracle and/or its affiliates. All rights reserved. |

Safe Harbor Statement

The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

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Oracle Database 18cAnd other unrelated topics

Nigel BaylissOptimizer PMhttp://blogs.oracle.com/optimizer

@vldbb

September 2018

http://blogs.oracle.com/optimizer


Program Agenda

Oracle Database 18c/ADWC

Navigating the Adaptive Optimizer

Oracle Database 12c

Fourth topic

Fifth topic

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2

3

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5

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Copyright © 2018, Oracle and/or its affiliates. All rights reserved. | 5

A Subjective Guide

New Optimizer Features and Enhancements

Oracle Database 11g

Oracle Database 12cRelease 1


Oracle Database 18c

[12.2.0.2]


A Subjective Guide

New Optimizer Features and Enhancements

Oracle Database 11g



Oracle Database 18c

A focus on Oracle Autonomous Data Warehouse Cloud(ADWC)

https://cloud.oracle.com/en_US/datawarehouse


Oracle Database 18c

7


Oracle Database 18c

Top-N Approximate Queries

Plan Stability in Standard Edition

ADW…

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2

3

8


Top-N Approximate Query

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• Approximate query processing background

• Approximate results for common top n queries

– How many approximate page views did the top five blog posts get last week?

–What were the top 50 customers in each region that spend most?

• Using much less resource yet yielding high accuracy

–Order of magnitudes smaller memory usage

–Max error < 0.7% * total number of rows


Top-N Approximate Query

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• New approximate functions APPROX_COUNT(), APPROX_SUM(), APPROX_RANK()

SELECT deptno, job, APPROX_SUM(sal), APPROX_COUNT(*)FROM empGROUP BY deptno, jobHAVING APPROX_RANK(partition by deptno ORDER BY APPROX_SUM(sal) desc) <= 2AND APPROX_RANK(partition by deptno ORDER BY APPROX_COUNT(*) desc) <= 3;

https://github.com/oracle/oracle-db-examples/tree/master/optimizer/topn


Oracle Database 18c

Top-N Approximate Queries

Plan Stability in Standard Edition

ADW…

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2

3

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Plan Stability in Standard EditionStored outlines an plan stability in SE

• Stored outlines were deprecated in Oracle Database 11g Release 1

• Stored outlines are still often used in Oracle Standard Edition to control SQL execution plans

• Stored outlines still function in Oracle Database 18c

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Subset of SQL Plan Management in Standard EditionPlan stability for Standard Edition

• Prior to Oracle Database 18c, SPM was an EE-only feature

• Oracle Database 18 Release 1 Standard Edition includes a subset of EE SQL plan management features

– Similar capabilities to stored outlines

• Easy migration from stored outlines to SQL plan baselines– DBMS_SPM.MIGRATE_STORED_OUTLINE()

• Control plans using SPM rather than stored outlines...

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Stored outlines are no longer needed

Example Use-Case with SPM in Standard Edition

FULL INDEX

HintedTest

Query

INDEX

SQL Plan Baseline

SELECT SUM(value)FROM salesWHERE region_id = :1

Better plan has been hinted

Plan is nowfully constrained

https://github.com/oracle/oracle-db-examples/tree/master/optimizer/spm_plan_control/SE

BUG 27500184 - CURSOR WITH DIFFERENT PLAN TO SQL PLAN BASELINE IS INVALIDATED REPEATEDLY IN SE

SELECT /*+ INDEX(..) */ SUM(value)

FROM salesWHERE region_id = :1


Capability is similar to stored outlines

Subset of SQL Plan Management in Standard Edition

Standard Edition Enterprise Edition

Multiple SQL plan baselines per SQL statement

Plan Evolution

Auto Capture

Capture from SQL Tuning Set

Capture from cursor cache

Capture from AWR

Auto purge unused SQL plan baselines

Export/Import (pack/unpack)

Convert stored outlines to SPBs


ADWC

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Extended Online Statistics GatheringADWC Focus

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Online Statistics Gathering: Pre-18c Behavior

• Gather statistics on load for empty tables only

• Non-partitioned table or extended syntax INSERT

• Direct path load only – single table or partition (with extended syntax)

– INSERT /*+ APPEND */

– Create Table As Select (CTAS)

• Histograms are not created

– Use GATHER AUTO after load to create them

• Creates synopses automatically if incremental statistics are enabled

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Extended Online Statistics Gathering

• Gathers statistics on load for non-empty tables

• Direct path load (DPL) only

– INSERT /*+ APPEND */

• Existing histograms are maintained automatically

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https://github.com/oracle/oracle-db-examples/tree/master/optimizer/autonomous/stats_on_load


Statistics-Based Query TransformationADWC Focus

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Statistics-Based Query Transformation

• For aggregate queries such as MIN/MAX/COUNT, the Oracle Database may need to scan all rows to calculate the value (if there are no WHERE-clause predicates)

• Table scans can be time-consuming

• When statistics are gathered, the database retains information on how may rows there are as well as details of column data such minimum and maximum values and the number of distinct values (NDV)

• If the database is sure that statistics are up-to-date, then it is in a position to answer some queries using the information it has already gathered

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ADWC Example

Statistics-Based Query Transformation

select max(num0),min(num1) from fact1;

---------------------------------------------------------------| Id | Operation | Name |---------------------------------------------------------------| 0 | SELECT STATEMENT | || 1 | RESULT CACHE | cpuu29wy174jfbu3a7zcxzkw12 || 2 | VIEW | VW_SQT_65BBF4BE || 3 | SORT AGGREGATE | || 4 | PX COORDINATOR | || 5 | PX SEND QC (RANDOM) | :TQ10000 || 6 | SORT AGGREGATE | || 7 | PX BLOCK ITERATOR | ||* 8 | TABLE ACCESS FULL| FACT1 |---------------------------------------------------------------


Supported

• Tables and views

• Create table as select

• MIN/MAX [Number/Date]

• approx_count_distinct

• COUNT()

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https://github.com/oracle/oracle-db-examples/tree/master/optimizer/autonomous/stats_answering


Restrictions• Queries must not have:

– WHERE clause

– Group By

– Join

– Non-merged view

– Connect By

• Not supported:

– Fixed tables

– GTTs

– WITH (cursor-specific temp table)

– Query TABLE function

– Table partition (via extended table syntax) – not in ADWC yet anyway

– SYS objects

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Restrictions

• Transformation is not used inside transaction

– YES: DML, commit, Q1

– NO: DML, Q1

• Stats branch is serial in PX queries

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Hint Parameters

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Hint Parameters Are No Longer Hidden

• optimizer_ignore_hints

• optimizer_ignore_parallel_hints

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Navigating the Adaptive Optimizer

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Oracle Database 11g11g Optimizer

Column Usage Statistics

Answers the question,"How are columnsused in queries?"

This metadata is persisted to the data dictionary G a t h e r S t a t i s t i c s

F O R A L L C O L U M N SS I Z E A U T O( t h e d e f a u l t )

HistogramsBetter statistics forskewed datasets

Learn frompreviousexecutions (on aquery-by-querybasis)

Information isheld in memoryand lost when query is aged out

Cardinality Feedback

The DataDictionary


Dynamic Sampling In Oracle Database 11g11g Optimizer


Histograms

DynamicSampling

Sample data toaccount for missingor inadequatestatistics/* OPT_DYN_SAMP */


The Adaptive Optimizer

New in Oracle Database 12c Release 1

12c Optimizer

AdaptiveStatistics

Optimizer Adaptive Features

Change SQL execution plans at runtimeLearn from previous executions and choose better SQL execution plans

AdaptivePlans


From Oracle Database 12cRelease 1

The Oracle Optimizer in Oracle Database 12c12c Optimizer


SQL Plan Directives

The lessons learnedfrom previous executions are SHAREDbetween queries

Statistics feedbackincludes joins

DynamicStatistics"DS_SVC"

AdaptivePlans

Adapt at runtime


From Oracle Database 12cRelease 1

Oracle Optimizer Adaptive Features12c Optimizer


SQL Plan Directives


G a t h e r S t a t i s t i c s

Column groupstatistics createdautomatically

G a t h e r S t a t i s t i c sF O R A L L C O L U M N SS I Z E A U T O

Histograms


AdaptivePlans


Viewing Optimizer Metadata

• DBA_SQL_PLAN_DIRECTIVES

• HISTOGRAM column in DBA_TAB_COLUMNS

• DBA_STAT_EXTENSIONS

• SELECT DBMS_STATS.REPORT_COL_USAGE('SH,'EMP')FROM DUAL;–SYS.COL_USAGE$

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Example Parameter SettingsFYI - Not recommended

Oracle Database 12c Release 1 12c Optimizer

SQL Plan Directives


DynamicStatistics"DS_SVC"_optimizer_dsdir_usage_control = 0

_optimizer_ads_use_result_cache = FALSE

Removes... /*+ RESULT_CACHE ... */

"_fix_control"='20243268: OFF'


FYI - Not recommendedX-Instance and PX

Oracle Database 12c Release 1 12c Optimizer


Adaptive DynamicStats for PX and X-Instance Queries

"_fix_control"='12914055:OFF'

12.2…optimizer_adaptive_statistics = FALSE

(_optimizer_ads_for_pq)


Oracle Database 12c Release 2

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Controlling adaptive features


12c Optimizer

AdaptiveStatistics


Change plans at runtime Learn from previous executions

OPTIMIZER_ADAPTIVE_FEATURES

AdaptivePlans


Finer control of adaptive features – new database parameters

From Oracle Database 12c Release 2

12c Optimizer

AdaptiveStatistics



OPTIMIZER_ADAPTIVE_FEATURES Obsolete

OPTIMIZER_ADAPTIVE_PLANS OPTIMIZER_ADAPTIVE_STATISTICS

AdaptivePlans


OPTIMIZER_ADAPTIVE_STATISTICS (FALSE)

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New default behavior

From Oracle Database 12c Release 2

12c Optimizer

AdaptiveStatistics



OPTIMIZER_ADAPTIVE_PLANS (TRUE)

AdaptivePlans



Oracle Optimizer Adaptive Features – Fully Adaptive12c Optimizer


SQL Plan Directives


G a t h e r S t a t i s t i c s

Column groupstatistics createdautomatically

G a t h e r S t a t i s t i c sF O R A L L C O L U M N SS I Z E A U T O

Histograms


AdaptivePlans



Oracle Optimizer Adaptive Features – Fully Adaptive12c Optimizer


SQL Plan Directives


G a t h e r S t a t i s t i c sG a t h e r S t a t i s t i c sF O R A L L C O L U M N SS I Z E A U T O

Histograms


AdaptivePlans

No.../*+ RESULT_CACHE */

DBA_SQL_PLAN_DIRECTIVES

instead



Oracle Optimizer Adaptive Features – New Defaults12c Optimizer


SQL Plan Directives

Statistics feedbacknot including JOINS


Histograms

DynamicStatistics

AdaptivePlans

/* OPT_DYN_SAMP */





SQL Plan Directives



Histograms

DynamicStatistics

AdaptivePlans

PX and X-Instance also use /* OPT_DYN_SAMP */





SQL Plan Directives



Histograms

DynamicStatistics

AdaptivePlans

DBMS_STATS preference:AUTO_STAT_EXTENSIONSDefault is OFF

Defaults:

OPTIMIZER_ADAPTIVE_PLANS=TRUE

OPTIMIZER_ADAPTIVE_STATISTICS=FALSE





SQL Plan Directives



Histograms

DynamicStatistics

OPTIMIZER_ADAPTIVE_PLANS=FALSE


= Always Enabled





SQL Plan Directives



Histograms

DynamicStatistics

OPTIMIZER_ADAPTIVE_PLANS=FALSE


Bug 25058954 : [BUGDB] HIGH FOREGROUND CPU IN 12.2 UNDER SQL PLAN DIRECTIVE

Fixed in 12.2.0.1


Oracle Database 12c Release 1Options and Recommendations

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• Set optimizer_adaptive_features=FALSE–Prioritizes stability and new features are available

–optimizer_dynamic_sampling = 0 is not usually necessary but it's an option

–Upgrading to 12.2 defaults: optimizer_adaptive_plans=TRUE and statistics feedback will kick in (without joins)

• Set optimizer_features_enable='11.2.0.4'–"Quick fix"

–More testing required for upgrade 12.1->12.2

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Adaptive Features = FALSE

Oracle Optimizer Adaptive Features – Release 112c Optimizer



Histograms

DynamicStatistics

OPTIMIZER_ADAPTIVE_FEATURES=FALSE


Oracle Database 12c Release 1 - Recommendation• Install latest Proactive Bundle Patch (>=October 2017)

– e.g. January 2018, Patch 27010930 - Database Proactive Bundle Patch 12.1.0.2.180116

• Recommendations for Adaptive Features in Oracle Database 12c Release 1 (Adaptive Features, Adaptive Statistics and 12c SQL Performance) (Doc ID 2312911.1)

– _fix_control='26664361:7','16732417:1','20243268:1'

• Remove optimizer_adaptive_features parameter from pfile/spfile

• Set the following optimizer parameters (these are the defaults in 12cR2 and 18c):

– optimizer_adaptive_plans=TRUE

– optimizer_adaptive_statistics=FALSE

– Because: BUG 27626925 - OPTIMIZER ADAPTIVE STATS DEFAULT FALSE NOT HONORED WHEN ENABLED IN OCT OR JAN BP

• On the database, execute the following ('OFF' is the default)

– EXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_STAT_EXTENSIONS','OFF')

• Testing will be required if patches are enabled because plans may change

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MT-Related Issues – pre Oracle Database 12c Release 2

BUG 24321547 - MODIFIED UNDERSCORE PARAMETER VALUES NOT VISIBLE IN PDB AFTER RESTART Available in 12.1.0.2 as a one-off, and included in Proactive Bundle Patch 180717 onwards.

BUG 20700587 - PDB DOESN'T TAKE UNDERSCORE PARAMETERS DURING DATABASE START

BUG 20020430 - PROBLEM WITH UMBRELLA PARAMETER CASCADING

BUG 28519141 - ALTER SESSION SET CONTAINER DOES NOT SET PARAMETERS DEPENDING ON PDB PARAMETERS


Using 12.2-style parameters on selected PDBs

Recipe - pre Oracle Database 12c Release 2

Clean

REM will report errors if the parameters are not currently included in the parameter filealter system reset "_fix_control";alter system reset optimizer_adaptive_features;alter system reset optimizer_adaptive_plans;alter system reset optimizer_adaptive_statistics;alter system reset "_optimizer_dsdir_usage_control";alter system reset "_optimizer_use_feedback_for_join";alter system reset "_optimizer_ads_for_pq";CDB

REM set defaults for fix control and dependent hidden parametersalter system set "_fix_control" = '26664361:0','16732417:0','20243268:0' scope=spfile;alter system set "_optimizer_dsdir_usage_control" = 126 scope = spfile;alter system set "_optimizer_use_feedback_for_join" = true scope = spfile;alter system set "_optimizer_ads_for_pq" = true scope = spfile;PDB

REM set recommended values for fix control and parameters, plus dependent hidden parametersalter system set "_fix_control" = '26664361:7','16732417:1','20243268:1' scope=spfile;alter system set optimizer_adaptive_plans = true scope = spfile;alter system set optimizer_adaptive_statistics = false scope = spfile;alter system set "_optimizer_dsdir_usage_control" = 0 scope = spfile;alter system set "_optimizer_use_feedback_for_join" = false scope = spfile;alter system set "_optimizer_ads_for_pq" = false scope = spfile;


Default Adaptive Features

Oracle Optimizer Adaptive Features – Release 1 + BP12c Optimizer


SQL Plan Directives

Statistics feedbackno join card f/b

DynamicStatistics

AdaptivePlans


Histograms

Defaults:

OPTIMIZER_ADAPTIVE_PLANS=TRUE



Oracle Database 12c and 18c - Recommendation

• Use the defaults–OPTIMIZER_ADAPTIVE_PLANS=TRUE

–OPTIMIZER_ADAPTIVE_STATISTICS=FALSE

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Adaptive Statistics

• Queries are longer-running

• Queries are complex

• Schema is complex

• Data distribution is complex

• Ad-hoc query environments–SQL plan directives allow the optimizer to learn from

queries and share this information with others

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System Statistics

• The default settings are appropriate for most systems

• Oracle recommends you don't gather them–EXADATA option can be useful in pure

DW workloads on engineered systems

• If you do not intend to gather system statistics, delete them and restart your initial database

• Always test any changes you make

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https://blogs.oracle.com/optimizer/should-you-gather-system-statistics



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Oracle Database 18c

Cost-based OR Expansion Transformation

Incremental Statistics

SQL Plan Management

Statistics Advisor

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2

3

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• Example – Convert query containing disjunctions (ORs) to UNION-ALLs

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SELECT * FROM prods T1, shops T2 WHERE (T1.vendid1 = 10 OR T2.vendid2 = 20) AND T1.delivery_batch = T2.delivery_batch;

SELECT * FROM prods T1, shops T2 WHERE T1.vendid1 = 10AND T1.delivery_batch = T2.delivery_batch UNION ALLSELECT * FROM prods T1, shops T2 WHERE T2.vendid2 = 20 AND T1.delivery_batch = T2.delivery_batchAND LNNVL(T1.vendid1=10);

Note: The LNNVL() function avoids duplicates

Opportunity to find newaccess paths


Cost-Based OR Expansion Transformation

• Limitations of pre 12.2 OR expansion– Cannot leverage other query transformations on top of OR expansion

– Cannot parallelize CONCATENATION branches

• New in 12.2:– Uses UNION ALL instead of CONCATENATION

–Opportunity for other transformations to be applied on top of UNION ALL branches

– Can execute UNION ALL branches in parallel

–OR expansion using Disjunctive Normal Form (DNF) and UNION ALL

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Comparing 11g OR Expansion with 12c Cost-Based OR Expansion

---------------------------------------------------| Id | Operation | Name |---------------------------------------------------| 0 | SELECT STATEMENT | || 1 | SORT AGGREGATE | || 2 | CONCATENATION | ||* 3 | HASH JOIN | || 4 | TABLE ACCESS FULL | T_4K || 5 | MERGE JOIN CARTESIAN | ||* 6 | INDEX FAST FULL SCAN | T_4K_CONCAT4 || 7 | BUFFER SORT | || 8 | INDEX FAST FULL SCAN| T_10K_HUNDRED ||* 9 | HASH JOIN | || 10 | NESTED LOOPS | ||* 11 | TABLE ACCESS FULL | T_4K ||* 12 | INDEX RANGE SCAN | T_10K_HUNDRED ||* 13 | INDEX FAST FULL SCAN | T_4K_CONCAT4 |---------------------------------------------------

---------------------------------------------------------| Id | Operation | Name |---------------------------------------------------------| 0 | SELECT STATEMENT | || 1 | SORT AGGREGATE | ||* 2 | HASH JOIN | || 3 | VIEW | VW_JF_SET$9CE2290B || 4 | UNION-ALL | ||* 5 | HASH JOIN | ||* 7 | INDEX FAST FULL SCAN | T_4K_CONCAT4 ||* 9 | TABLE ACCESS FULL | T_4K ||* 10 | HASH JOIN | ||* 11 | TABLE ACCESS FULL | T_4K || 12 | INDEX FAST FULL SCAN | T_4K_CONCAT3 || 13 | INDEX FAST FULL SCAN | T_10K_HUNDRED |---------------------------------------------------------

SELECT COUNT(*)FROM t_4k T1, t_4k T2, t_10k T3WHERE T1.ten = T2.ten AND

T1.hundred = T3.hundred AND(T1.unique1 = 10 OR T2.unique2 = 20);

Pre-12.2 12.2

Note that T_10K_HUNDRED is scanned only once in the 12.2 case.


4

Oracle Database 18c



SQL Plan Management

Statistics Advisor

1

2

3

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Incremental Maintenance for Partitioned Tables

Global table statisticsmust be maintained…

• Total #rows• Min/Max• Number of distinct values


Incremental Maintenance for Partitioned Tables


Incremental Maintenance Overview for Partitioned Tables • Incremental maintenance (introduced in 11.1) significantly expedites statistics

gathering on partitioned tables– Only partitions with stale statistics have statistics re-gathered

– Global statistics derived from partition level statistics

• Typical usage– Tables range partitioned on dates and only the last few partitions have data changes

• exec dbms_stats.set_table_prefs (user,'apptab','INCREMENTAL','TRUE')

• exec dbms_stats.set_global_prefs('INCREMENTAL_STALENESS', 'USE_STALE_PERCENT')

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Synopses

• Each partition maintains synopses in incremental mode

• Synopses are detailed information about Number of Distinct Values (NDV)

• Global level NDV is derived by aggregating synopses

• Synopses stored on disk in SYSAUX tablespace

• However: synopses can be large when …

– Large number of partitions

–Many columns in the table

– NDV in each partition is high

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Controlling the Synopsis Generation Algorithm in 12.2

• Previous algorithm is still supported!

• DBMS_STATS preference provided to control which algorithm to use

– Preference name: APPROXIMATE_NDV_ALGORITHM

– Preference value:

• “REPEAT OR HYPERLOGLOG” (default):– If synopses of old format exists, continue using the pre-12.2 algorithm

– If no synopses yet or synopses are in new format, use the new 12.2 algorithm

• “ADAPTIVE SAMPLING”– Force to use pre-12.2 adaptive sampling algorithm

– Any synopses in new 12.2 format are deleted and the stats are regathered

– Preserves behavior prior to 12.2

• “HYPERLOGLOG”– Force use of new algorithm

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DBMS_STATS.SET_TABLE_PREFS…


Preference: HYPERLOGLOGReplacing old format with new

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SALESSYSAUX Tablespace

P1

P2

P1 has a synopsisin pre-12.2 format

Re-gatherStatistics P1

New synopsisfor P1 in compact12.2 format

PartitionedTable


Preference: REPEAT OR HYPERLOGLOGCoexisting Old and New Formats

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SALESSYSAUX Tablespace

P1

P2

P1 has a synopsisin pre-12.2 format

Synopsis forP2 in compact12.2 format

GatherStatistics

PartitionedTable

https://github.com/oracle/oracle-db-examples/tree/master/optimizer/new_synopses


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Oracle Database 18c



SQL Plan Management

Statistics Advisor

1

2

3

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SQL Plan Management AWR Capture

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• Manually capture SQL plans from AWR:

– dbms_spm.load_plans_from_awr(begin_snap => 5, end_snap => 8);


SQL Plan Baseline Auto Capture

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• In 12.1, automatic capture applies to all repeatable queries

– Includes many non-critical queries, wasting storage space in SYSAUX

• In 12.2, capture only what you need

– Specific applications and schemas

– Filter the SQL statements you need• SQL Text

• Parsing Schema

• Module

• Action

ExecutionPlan

Execute

SQL PlanBaselines

12.2


SQL Plan Management Auto Capture

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• Set filters for automatic capture:

– dbms_spm.configure('AUTO_CAPTURE_PARSING_SCHEMA_NAME',

'SCOTT', TRUE);

– Current filter settings stored in DBA_SQL_MANAGEMENT_CONFIG


4

Oracle Database 18c



SQL Plan Management

Statistics Advisor

1

2

3

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Inferior Statistics Cause Problems

• Inferior statistics cause query performance problems

• For example:

– Stale, out of date statistics

–Missing statistics

– Poor quality – ignoring recommended approaches

– Inconsistencies between tables and indexes

– Inconsistencies between primary-key/foreign-key relationships

• Problems can be difficult to diagnose– Resulting in time-consuming analysis and MOS Service Requests

76


Why Might You Have Inferior Statistics?• Oracle continuously enhances statistics gathering features but

enhancements can be overlooked post-upgrade

– For example: Auto Sample Size

• DBAs may use legacy scripts to gather statistics manually

– Reluctance to change “proven” procedures

• Statistics gathering can be overlooked because of inexperience

• Statistics might not be maintained during batch processing– Developer inexperience or perceived lack of time in batch window

• Not all DBAs read best practice white papers

• “Inherited” systems where nobody understands the scripts

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The Optimizer Statistics Advisor

• Rules that have not been followed will generate findings

• Findings can lead to specific recommendations

• Recommendations can be implemented using actions

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Rules Findings Recommendations Actions


A Specific Example

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Use default parameters in DBMS_STATS.GATHER...STATS

ESTIMATE_PERCENT=>0.01 is used in maintenance scripts

Use default ESTIMATE_PERCENT (AUTO_SAMPLE_SIZE)

GATHER_DATABASE_STATS(obj_filter_list)


Optimizer Statistics Advisor Task

• Advisor task gathers and stores data

– Low performance overhead

– DBA can choose which rules are applicable using filters

– Filters can also constrain the scope of the task (tables, schemas and so on)

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DataDictionary


Optimizer Statistics Advisor Reports and Action Script

• Reports are generated from retained task data

• Generate the HTML or text-based report

• Generate the action SQL script

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TaskData

HTML

SQL


Flow Summary

• Create task:– dbms_stats.create_advisor_task('q1_advisor_run');

• Optionally, configure a filter:– dbms_stats.configure_advisor_filter ('q1_advisor_run' ...);

• Manually execute the advisor:– dbms_stats.execute_advisor_task('q1_advisor_run');

• Generate the report:– dbms_stats.report_advisor_task('q1_advisor_run', ftype=>'html' ...);

– Use AUTO_STATS_ADVISOR_TASK as task name for automatic task

• Generate the action script:– dbms_stats.script_advisor_task('q1_advisor_run');

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Safe Harbor Statement

The preceding is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

83

safe harbor statement · the oracle optimizer in oracle database 12c 12c optimizer column usage...

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