1. MAKE YOUR QUERIES FASTER
Optimization Optimization
MAKE YOUR QUERIES FASTER
MATT MARTIN
SQL Saturday Atlanta
June 2017

2. About Enjoy Big Data projects and query tuning 9 years experience
MATT MARTIN | CHIEF TECHNOLOGY OFFICER | SQLETL
Website:
9 years experience
SQL Server, SSIS, EDIS, and Big Data
Enjoy Big Data projects and query tuning

3. Agenda Mega Chainsaws Corp. Cool Stuff this course will teach you
Company Sales Database Overview
Tables involved in Sales Query
Identify bottlenecks
Restructure query to run faster
Q & A
Cool Stuff this course will teach you
How to generate random data of any size/type
How to size all tables in a database
How to read an execution plan and identify opportunities for performance gains

4. 1. Mega Chainsaws Corp Time to Generate some data USE MEGA_CHAINSAWSGO
exec USP_LOAD_DUMMY_DATA_TO_DB

5. 1. Mega Chainsaws Corp Tip 1: Know your data size USE MEGA_CHAINSAWS
Table Name
Data Description
CUST_ID
Customer information (names)
DPT
Departments
INVC_DTL
Invoice line detail
INVC_HDR
Invoice header
INVC_STAT_CD
Invoice status
PO_DTL
Purchase order detail
PO_HDR
Purchase order header
PO_STAT_CD
PO status code
PO_SUB_STAT_CD
PO sub status code
SKU
Product sku/description/retail
SKU_STAT_CD
SKU status (active/clearance/inactive)
SLS_REP_ID
Sales Rep name
SLS_REP_STAT_CD
Employee Status Code (Active/Term)
Tip 1: Know your data size
USE MEGA_CHAINSAWS GO
exec usp_get_tbl_sizes

6. 2. Examine Slow Query Over a dozen table joins
Clustered Indexes on larger tables do not align (PO_DTL and INVC_DTL)
LIKE statement in the WHERE clause multiple times, combined with OR

7. 2. Bottlenecks to look for
SELECTS in the WHERE clause
Range Joins
Like Operators
Non-covering indexes
Clustered Indexes not aligning and forcing a hash join on large tables
AND IHDR.INVC_DT = (SELECT MAX(INVC_DT) FROM INVC_HDR WHERE INVC_ID = IHDR.INVC_ID)
AND IHDR.INVC_DT BETWEEN POH.ORD_DT AND DATEADD(DAY,90, POH.ORD_DT)
OR lower(C.CUST_NM) LIKE '%alvarez%'

8. 3. Current Execution Plan
Biggest Performance Killers
Hash Matches
Full Table Scans (no index)

9. 3. Optimize this Query Break your query into smaller chunks
Leverage SELECT INTO statements (They are fast)
Use temp tables to pre-process data

10. Walk through new Stored Proc
3. Optimize this Query
Walk through new Stored Proc

11. 4. Take-aways
Do not fall in the trap of optimization to death. Is it really worth an extra 3-4 hours of work to shave off another 5 seconds on a query?
Know your data size. Small tables are not worth your time to optimize queries against. Odds are it will run a full table scan anyways due to diminished returns on optimization
Check your clustered indexes for header/detail relational tables. If you can leverage an Identity seed as the clustered index for the header and detail, almost always do it. Why?
- The optimizer has to compare 1 column to merge the two tables against and its an integer so it will be fast

12. Optimization Optimization
MATT MARTIN
CTO | SQLETL
Website: