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8f889b1083
This SQL-standard feature allows a sub-SELECT yielding multiple columns (but only one row) to be used to compute the new values of several columns to be updated. While the same results can be had with an independent sub-SELECT per column, such a workaround can require a great deal of duplicated computation. The standard actually says that the source for a multi-column assignment could be any row-valued expression. The implementation used here is tightly tied to our existing sub-SELECT support and can't handle other cases; the Bison grammar would have some issues with them too. However, I don't feel too bad about this since other cases can be converted into sub-SELECTs. For instance, "SET (a,b,c) = row_valued_function(x)" could be written "SET (a,b,c) = (SELECT * FROM row_valued_function(x))".
51 lines
1.7 KiB
C
51 lines
1.7 KiB
C
/*-------------------------------------------------------------------------
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*
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* tlist.h
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* prototypes for tlist.c.
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*
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*
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* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/optimizer/tlist.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef TLIST_H
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#define TLIST_H
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#include "optimizer/var.h"
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extern TargetEntry *tlist_member(Node *node, List *targetlist);
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extern TargetEntry *tlist_member_ignore_relabel(Node *node, List *targetlist);
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extern TargetEntry *tlist_member_match_var(Var *var, List *targetlist);
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extern List *flatten_tlist(List *tlist, PVCAggregateBehavior aggbehavior,
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PVCPlaceHolderBehavior phbehavior);
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extern List *add_to_flat_tlist(List *tlist, List *exprs);
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extern List *get_tlist_exprs(List *tlist, bool includeJunk);
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extern int count_nonjunk_tlist_entries(List *tlist);
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extern bool tlist_same_exprs(List *tlist1, List *tlist2);
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extern bool tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK);
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extern bool tlist_same_collations(List *tlist, List *colCollations, bool junkOK);
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extern TargetEntry *get_sortgroupref_tle(Index sortref,
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List *targetList);
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extern TargetEntry *get_sortgroupclause_tle(SortGroupClause *sgClause,
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List *targetList);
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extern Node *get_sortgroupclause_expr(SortGroupClause *sgClause,
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List *targetList);
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extern List *get_sortgrouplist_exprs(List *sgClauses,
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List *targetList);
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extern Oid *extract_grouping_ops(List *groupClause);
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extern AttrNumber *extract_grouping_cols(List *groupClause, List *tlist);
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extern bool grouping_is_sortable(List *groupClause);
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extern bool grouping_is_hashable(List *groupClause);
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#endif /* TLIST_H */
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