Tuning SQL for Optimal Performance - Sybase

Agenda
• What affects application
performance
• SQL Optimization and the
Application Lifecycle
• How to achieve and maintain
maximum performance
• Interview with Michael
Brundige, Sr. Sybase DBA
of Brinks

Gartner Study
• According to industry experts,
60% to 90% of database
application performance
problems are caused by SQL
SQL
Related
60%
“Poorly written OLTP application SQL continues to be the
largest contributor to poor database performance.”
Other
40%
– Gartner Group

A Corporate Performance Strategy
• Hardware Upgrades 0 — 25%
• Operating System Settings 0 — 50%
• Database Server Parameter Settings 0 — 100%
• Database Design 0 — 1000%
• Indexes on Database Tables 0 — 1000%
• SQL Statements 0 — 100,000%
Based on LECCOTECH customer feedback

Sample of Customer Results
Fremont Compensation – resource consumption
Original statement: 2.5 hours SQL Expert optimized result: 1.5 minutes
Original statement: 4 hours SQL Expert optimized result: 1.3 minutes
Original statement: 8 hours SQL Expert optimized result: 2 hours
Metasolv, Plano, TX – productivity
Original statement: 15 minutes SQL Expert optimized result: 3 seconds
Kentucky Community Technical Colleges – skill set
Original statement: 1.2 hours SQL Expert optimized result: 15 seconds
(complex statement with 8 table joins)

Sybase SQL Expert: A Performance Assurance Strategy
Enhancements or
New Requirements
Maintain
Optimal
Performance
The Application Life-Cycle
Development
Production
QA & Stress
Best
Performing
Code
Maximum
Performance
Before Rollout

3-Golden Rules for Writing SQL
• Make it work
• Make it work right
• Make it work fast

The Complex Nature of SQL
• Difficult to write SQL for performance
• Many ways to write a SQL
• Small differences in coding SQL can have great performance
implications
• Need constant tuning due to data and system environment
changes
• Most important factor to system scalability

How to Tune SQL
• Understand how the database processes SQL statements
• Know database structure
• Know data in the database
• Different SQL syntax can change performance

How Does ASE Process SQL?
Data
SQL
Server Receives SQL
Parse, Normalize &
Pre-Process
ASE Optimizer
Determines the Query Plan
Bind
Execute

How the ASE Optimizer Works*
SQL
Internally
Rewrites &
Generates
Multiple
Query plans
Plan 1 cost=1000
Plan 2 cost=3000
Plan 3 cost=500
Plan 1
Plan 2
Plan 3
Cost Estimation

How the ASE Optimizer Works*
SQL
Internally
Rewrites &
Generates
Multiple
Query plans
Plan 1 cost=1000
Plan 2 cost=3000
Plan 3 cost=500
Plan 1
Plan 2
Plan 3
Can it try every possible
way to rewrite your SQL?
Cost Estimation

How the ASE Optimizer Works*
SQL
Internally
Rewrites &
Generates
Multiple
Query plans
Plan 1 cost=1000
Plan 2 cost=3000
Plan 3 cost=500
Plan 1
Plan 2
Plan 3
Can it try every possible
way to rewrite your SQL?
Cost Estimation
How Accurate is the
Cost Estimation
Execution

The Perfect Optimizer?
“For any real-life optimizer, no matter how sophisticated, there will
always be a query, a database state and a system state where the
optimizer makes the wrong decision.”
Mihnea Andrei (Sybase France) &
Patrick Valduriez (Laboratoire d’Informatique de Paris)
User-Optimizer Communication, Abstract Plans Tech paper

2 Different SQL’s – Same Query Plan
Elapsed Time: 0.080 s Elapsed Time: 0.080 s

2 Different SQL’s – 2 Different Plans
Elapsed Time: 0.080 s Elapsed Time: 0.110 s

Find the Best Way to Process Your SQL

Find the Best Way to Process Your SQL

Manual Approach – SQL Tuning
• Obtain show_plan and analyze output. Look for problem
operations such as full table scans
iSQL
SET SHOWPLAN ON
GO
SELECT *
FROM EMPLOYEE
WHERE EM P_ID > 73712
GO
SET SHOWPLAN OFF
GO
QUERY PLAN FOR STATEMENT 1 (at line 1).
STEP 1
The type of query is SELECT.
FROM TABLE
EMPLOYEE
Nested iteration.
Table Scan.
Forward scan.
Positioning at start of table.
Using I/O Size 2 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.
Total estimated I/O cost for statement 1 (at line 1): 20600.

Manual Approach – SQL Tuning
• Try different ways to write the SQL statement
• Techniques to write SQL:
– IN, EXISTS, or JOIN
– Full table scan, or index scan
– JOIN access path
– NOT IN, or MINUS
– Outer Join, or UNION ALL
– IN or OR
– Forces?
– Temp tables?
– ….

Article – Fifty Ways to Quote Your Query
BY C. J. Date, July 1998
Database Programming & Design
1. SELECT DISTINCT S.SNAME
FROM S, SP
WHERE S.S# = SP.S#
AND SP.P# = 'P2'
“if there are so many ways to
formulate such a simple query,
how many ways are there going
to be for a complicated one?”
2. SELECT DISTINCT S.SNAME
FROM S
WHERE S.S# IN
( SELECT SP.S#
FROM SP
WHERE SP.P# = 'P2' )
3. SELECT DISTINCT S.SNAME
FROM S
WHERE S.S# =ANY
( SELECT SP.S#
FROM SP
WHERE SP.P# = 'P2' )
4. SELECT DISTINCT S.SNAME
FROM S
WHERE S.S# MATCH
( SELECT SP.S#
FROM SP
WHERE SP.P# = 'P2' )
5. SELECT DISTINCT S.SNAME
FROM S
WHERE S.S# MATCH
UNIQUE
( SELECT SP.S#
FROM SP
WHERE SP.P# = 'P2' )
6. SELECT DISTINCT S.SNAME
FROM S
WHERE S.S# MATCH
PARTIAL
( SELECT SP.S#
FROM SP
WHERE SP.P# = 'P2' )

Manual Approach – SQL Tuning
• Time the alternatives in ISQL
iSQL
SET STATISTICS IO ON
GO
SET STATISTICS TIME ON
GO
SELECT *
FROM EMPLOYEE
WHERE EMP_ID > 73712
GO
SET STATISTICS IO OFF
GO
SET STATISTICS TIME OFF
GO
Server Message: Number 3631, Severity 10
Line 1:
Total actual I/O cost for this command: 0.
Total writes for this command: 0
Server Message: Number 3631, Severity 10
Line 1:
Total actual I/O cost for this command: 0.
Total writes for this command: 0
Execution Time 0.
SQL Server cpu time: 0 ms. SQL Server elapsed time: 3614 ms.
Parse and Compile Time 0.
SQL Server cpu time: 0 ms.
Table: EMPLOYEE scan count 1, logical reads: (regular=1030 apf=0 total=1030),
physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Server Message: Number 3631, Severity 10
Line 1:
Total actual I/O cost for this command: 2060.
Total writes for this command: 0
Execution Time 16.
SQL Server cpu time: 1600 ms. SQL Server elapsed time: 7730 ms.
(18371 rows affected)
Parse and Compile Time 0.
SQL Server cpu time: 0 ms.
Execution Time 0.
SQL Server cpu time: 0 ms. SQL Server elapsed time: 0 ms.
Parse and Compile Time 0.
SQL Server cpu time: 0 ms.

SQL Expert
• Streamlines the SQL optimization process
• Proactively identifies problematic SQL without running applications
• AI-based SQL transformation generates every possible alternative
and unique query plan
• Benchmarks SQL to identify the most efficient alternative for a db
environment
• Provide the “OPTIMUM” SQL alternative

SQL Optimization Methodology
Capture/Extract
Analyze
Maximize
Performance
Optimize

SQL Optimization Methodology
Capture/Extract
Analyze
Maximize
Performance
• Dynamic SQL:
Captures SQL through
the Sybase Monitor
Server
— SQL Monitor
Optimize
• Embedded SQL:
Extracts SQL from ASE
database objects (sp’s,
views, etc), files,
source code
(PowerBuilder, etc)
— SQL Scanner

SQL Monitor – Capture currently running SQL

SQL Scanner – Extract embedded SQL from db objects & source code

SQL Optimization Methodology
Capture/Extract
Analyze
• Analyze in batch the query plan for multiple SQL
• Identify potentially problematic operations: Full
tables scans-large tables, many table scans,
worktables,…
—SQL Scanner
Maximize
Performance
Optimize

SQL Scanner – Analyze and identify problematic query plans

Problematic SQL identified, without running it!

SQL Optimization Methodology
• AI based recursive SQL
transformation
• Provides unique query
plans
• Guarantees semantically
equivalence
• •Capture/Extract Rewrites SELECT,
SELECT…INTO,
INSERT, DELETE and
UPDATE
• Benchmarks test SQL
—Syntactical SQL Optimizer
Analyze
Maximize
Performance
Optimize

What is Recursive SQL Transformation
Using 2 transformation rules
SELECT * FROM A
WHERE EXISTS (SELECT ‘x’ FROM B
WHERE EXISTS (SELECT ‘x’ FROM C
WHERE B.C2=C.C2)
WHERE A.C1=B.C1)
IN to
EXISTS
SELECT * FROM A
WHERE A.C1 IN (SELECT B.C1 FROM B
WHERE EXISTS (SELECT ‘x’ FROM C
WHERE B.C2=C.C2 ))
EXISTS
to IN
SELECT * FROM A
WHERE A.C1 IN (SELECT B.C1 FROM B
WHERE B.C2 IN
(SELECT C.C2 FROM C))
EXISTS
to IN
IN to
EXISTS
SELECT * FROM A
WHERE A.C1 IN (SELECT B.C1 FROM B
WHERE EXISTS (SELECT ‘x’ FROM C
WHERE B.C2=C.C2 ))
SELECT * FROM A
WHERE EXISTS (SELECT ‘x’ FROM B
WHERE B.C2 IN (SELECT C.C2 FROM C)
AND A.C1=B.C1)
SELECT * FROM A
WHERE A.C1 IN (SELECT B.C1 FROM B
WHERE B.C2 IN (SELECT C.C2 FROM C))
SELECT * FROM A
WHERE EXISTS (SELECT ‘x’ FROM B
WHERE B.C2 IN (SELECT C.C2 FROM C)
AND A.C1=B.C1)
SELECT * FROM A
WHERE A.C1 IN (SELECT B.C1 FROM B
WHERE EXISTS (SELECT ‘x’ FROM C
WHERE B.C2=C.C2))
SELECT * FROM A
WHERE EXISTS (SELECT ‘x’ FROM B
WHERE EXISTS (SELECT ‘x’ FROM C
WHERE B.C2=C.C2)
AND A.C1=B.C1)

SQL Optimization – In 2 minutes, SQL Expert generated 279 alternatives

Benchmark testing the SQL alternatives against the database –
Locate the most–efficient SQL for the ASE environment

Original SQL
Elapsed Time: 0.763 s
Fastest SQL Alternative
Elapsed time: 0.060 s

Polling Question
Yes or No
Have you used ASE’s
Abstract Plans?

Abstract Plan
SQL
Optimizer
ASE
Based on the
database statistics
to generate a query
plan
Based on the saved
abstract plan to
generate a query
plan
Execution

Sybase SQL Expert Facts
• Sybase SQL Expert (SSE) is sold as an option to ASE
• Windows-based product, Client-based product, no server-side
installation
• Databases supported:
– From version 11.0 to ASE 12.5.0.3
– To capture SQL from the Sybase Monitor Server, ASE 11.5 or above required
– To use Abstract Plans, ASE 12.0 or above required
• Open Client/CT-Lib version 11 or above
• Sybase Monitor Server is only needed to capture currently running
SQL; you can use SQL Expert without the Sybase Monitor Server
• Non-intrusive
– Scanning and optimization process occurs in the PC; no over-head to the
database

Key SQL Expert Benefits
• Automates current manual tuning efforts
• Solves the problem consuming 60–90% of IT resources
• Delivers immediate and quantifiable application
performance gains
• Heightens staff expertise
• Increases staff productivity
• Establishes benchmarks and performance standards
Use Sybase SQL Expert to ensure only
the best performing statements are used.

Interview with Michael
Brundige, Sr. Sybase
DBA of Brinks