Fix performance regression in previous_version
function
#366
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#365 changed the definition of
previous_version
and introduced a performance regression.Update the function with extra
WHERE
clauses so that the recursive CTE can take better advantage of the table PK index.On a large (~1M record)
pgroll.migrations
table the query analysis for the recursive CTE is:Before:
After:
ie the recursive portion of the table is able to take advantage of the table's PK (defined on
(schema, name)
).