postgres

History

Richard Guo 247dea89f7 Introduce an RTE for the grouping step If there are subqueries in the grouping expressions, each of these subqueries in the targetlist and HAVING clause is expanded into distinct SubPlan nodes. As a result, only one of these SubPlan nodes would be converted to reference to the grouping key column output by the Agg node; others would have to get evaluated afresh. This is not efficient, and with grouping sets this can cause wrong results issues in cases where they should go to NULL because they are from the wrong grouping set. Furthermore, during re-evaluation, these SubPlan nodes might use nulled column values from grouping sets, which is not correct. This issue is not limited to subqueries. For other types of expressions that are part of grouping items, if they are transformed into another form during preprocessing, they may fail to match lower target items. This can also lead to wrong results with grouping sets. To fix this issue, we introduce a new kind of RTE representing the output of the grouping step, with columns that are the Vars or expressions being grouped on. In the parser, we replace the grouping expressions in the targetlist and HAVING clause with Vars referencing this new RTE, so that the output of the parser directly expresses the semantic requirement that the grouping expressions be gotten from the grouping output rather than computed some other way. In the planner, we first preprocess all the columns of this new RTE and then replace any Vars in the targetlist and HAVING clause that reference this new RTE with the underlying grouping expressions, so that we will have only one instance of a SubPlan node for each subquery contained in the grouping expressions. Bump catversion because this changes the querytree produced by the parser. Thanks to Tom Lane for the idea to invent a new kind of RTE. Per reports from Geoff Winkless, Tobias Wendorff, Richard Guo from various threads. Author: Richard Guo Reviewed-by: Ashutosh Bapat, Sutou Kouhei Discussion: https://postgr.es/m/CAMbWs4_dp7e7oTwaiZeBX8+P1rXw4ThkZxh1QG81rhu9Z47VsQ@mail.gmail.com		1 year ago
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appendinfo.h	Update copyright for 2024	2 years ago
clauses.h	Update copyright for 2024	2 years ago
cost.h	Treat number of disabled nodes in a path as a separate cost metric.	1 year ago
geqo.h	Update copyright for 2024	2 years ago
geqo_copy.h	Update copyright for 2024	2 years ago
geqo_gene.h	Update copyright for 2024	2 years ago
geqo_misc.h	Update copyright for 2024	2 years ago
geqo_mutation.h	Update copyright for 2024	2 years ago
geqo_pool.h	Update copyright for 2024	2 years ago
geqo_random.h	Update copyright for 2024	2 years ago
geqo_recombination.h	Update copyright for 2024	2 years ago
geqo_selection.h	Update copyright for 2024	2 years ago
inherit.h	Update copyright for 2024	2 years ago
joininfo.h	Update copyright for 2024	2 years ago
optimizer.h	Introduce an RTE for the grouping step	1 year ago
orclauses.h	Update copyright for 2024	2 years ago
paramassign.h	Add RETURNING support to MERGE.	2 years ago
pathnode.h	Treat number of disabled nodes in a path as a separate cost metric.	1 year ago
paths.h	Fix partitionwise join with partially-redundant join clauses	1 year ago
placeholder.h	Update copyright for 2024	2 years ago
plancat.h	Update copyright for 2024	2 years ago
planmain.h	Revert: Remove useless self-joins	1 year ago
planner.h	Re-allow planner to use Merge Append to efficiently implement UNION.	1 year ago
prep.h	Re-allow planner to use Merge Append to efficiently implement UNION.	1 year ago
restrictinfo.h	Update copyright for 2024	2 years ago
subselect.h	Update copyright for 2024	2 years ago
tlist.h	Update copyright for 2024	2 years ago