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sql: add virtual table pushdown infrastructure, and add to several spots #47316

Merged
merged 3 commits into from
Apr 25, 2020
Merged

sql: add virtual table pushdown infrastructure, and add to several spots #47316

merged 3 commits into from
Apr 25, 2020
+1,334 −823

Commits on Apr 25, 2020

  1. sql: support virtual tables in LookupTableByID

    @jordanlewis
    jordanlewis committed Apr 25, 2020
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  2. sql: add virtual table pushdown; some examples 

    This commit adds virtual table "indexes", a concept that allows virtual
tables to specify columns that can be accelerated given an equality
constraint using custom code.

For example, the information_schema.tables table contains one entry per
table in the database. Before this commit, retrieving the row for a
table 'foo' would require fetching the descriptors for all tables and
filtering for the one that had name 'foo'. Now, if there's a constraint
on the table name, an "index" is used that converts the name into a
descriptor with a single lookup.

This commit also adds virtual indexes to a few commonly-used virtual
tables. There is much, much more that could be done - the ones that are
added here are just examples.

Release note (performance improvement): filtered scans over virtual
tables have improved performance in common cases.
    @jordanlewis
    jordanlewis committed Apr 25, 2020
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  3. sql: SHOW CREATE takes advantage of virtual index 

    This commit updates the implementation of SHOW CREATE so that it doesn't
have to filter every single table in the database. It does 2 things:

1. Stop outputting zone configs in crdb_internal.create_statements
2. Start outputting partitioning status in the above instead
3. Get zone configs from the SQL query in SHOW CREATE with a subquery
   from the zone configs table and join together in SQL

This strategy makes it possible to give
crdb_internal.create_statements a virtual index.

Now SHOW CREATE is really fast!

Release note (performance improvement): SHOW CREATE is much more
efficient
    @jordanlewis
    jordanlewis committed Apr 25, 2020
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