Do not consider non-deterministic expressions as invariants in pre-filters #7853
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asfernandes
reviewed
Nov 20, 2023
src/jrd/SysFunction.cpp
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| const MetaName funcName(name); | ||
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| return (funcName != "GEN_UUID" && |
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I think this should be defined in table at SysFunction::functions.
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Only 5.x is checked now. |
dyemanov
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this pull request
Nov 16, 2024
…lters (#7853) * Do not consider non-deterministic expressions as invariants in pre-filters * Follow Adriano's suggestion * Allow deterministic uncorrelated subqueries to be considered as invariants
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Frontported to v6. |
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QA note: removed upper bound for version after this feature was front-ported to 6.x. Checked on 6.0.0.532. |
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Related to my prior commit for #1708. Even if the boolean does not access table fields it may still be non-deterministic, in this case it should not be treated as invariant and evaluated just once.
Example:
select count(*) from employee where rand() > 0.5The condition is not correlated with any data but still produces a different result per every invocation. Prior to v5, it returned (approximately) half rows of the result set. In v5, it returns either zero rows or a half of them, depending on what was the result of
RAND()during its first invocation.Tested with constant expressions,
RAND()and SQL functions defined as deterministic and non-deterministic. This patch does not detect determinism too deeply (e.g. whether a field references stream from the current scope or the outer one), only to the level currently needed for the optimizer.