Make sure we're using indexes during rollbacks 13.7.0.1#2084
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Fixes #2083 The `queryMinRefId` query uses ```sql SELECT id FROM <table> WHERE <field> >= $1 ORDER BY id ASC LIMIT 1. ``` The planner sometimes picks a bad plan: ```sql Index Scan using tx_pkey on tx Filter: (block_id >= $1) ``` the filter is not Index Cond, so this ends up in a sequential scan. The index refers to the primary key and is only used for sorting. Instead we use a simpler query without ORDER BY: SELECT id FROM <table> WHERE <field> >= $1 LIMIT 10000 This forces the planner to use the field's index. The results are fetched and the minimum is found in Haskell. Near the tip this returns only a handful of rows. If there are more than 10000 matching rows (large rollback), we fall back to the original ORDER BY id ASC LIMIT 1 query.
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Superseeded by #2080 |
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Fixes #2083 (comment)
The
queryMinRefIdquery usesThe planner sometimes picks a bad plan:
the filter is not Index Cond, so this ends up in a sequential scan. The index refers to the primary key and is only used for sorting. Instead we want to use
With this change we use
which forces a good plan:
making sure we're using the Index Cond