Understanding Indexes in KB_SQL March 2001 Just-in-Time Indexes March 2001 Understanding Indexes in KB_SQL March 2001

Learning Objectives What options do I have to improve query performance? The answer is…indexes. Review indexing strategies Introduce just-in-time indexes Discuss advantages and caveats

Improve Performance Why does my query run so slow?

Query Results

Show Plan/Stats: Query Run query with Show Plan and Show Stats

Show Plan: Results Note: No index being used

Show Stats: Results Note: Selecting 9 of 25000 rows searched

Show All Plans: Query Run query with SHOW_ALL_PLANS to see if index is available

Show All Plans: Results Note: No indexes available

Index Exists

Define Index to KB_SQL Add BY_NAME index in KB_SQL

New Show Plan Note: BY_NAME index is used, cost is reduced

New Show Stats Note: Selecting 9 of 9 rows searched

New Show All Plans Note: BY_NAME index available

How do we improve performance if we don’t have sufficient indexes? What are the options? Create supplemental table(s) Build index Create just-in-time index When will it be populated? How often should it be updated? Advantages and caveats?

Create Supplemental Tables Create new table Join to “base” table

Build the Index Benefits Caveats Queries only look at key data which results in faster searches Caveats Time Resources Additional globals to maintain

What if there is no index?

What if there is no index? (cont)

What if there is no index? (cont)

Just-in-Time Indexes When will the index be populated? How often should the index be updated?

Just-in-Time Indexes: Advantages and Caveats Advantages over traditional indexes Add only the indexes that the user demands Reduce wasted effort to build indexes that won’t be used Caveats Does not provide up-to-the-minute data accuracy 2 or more queries to realize benefit

Build the Just-in-Time Index

Define the Index to KB_SQL

New Show All Plans Note: Two indexes available; BY_SUPPLIER is accepted based on constraint

New Show Plan Note: BY_SUPPLIER index is used

New Show Stats Note: Selecting 4 of 4 rows searched

Summary Discussed options available to help improve query performance The answer is…indexes. Reviewed indexing strategies Introduced just-in-time indexes Discussed advantages and caveats