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Add notion of a "transform function" that can simplify function calls.

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Initially, we use this only to eliminate calls to the varchar()
function in cases where the length is not being reduced and, therefore,
the function call is equivalent to a RelabelType operation.  The most
significant effect of this is that we can avoid a table rewrite when
changing a varchar(X) column to a varchar(Y) column, where Y > X.

Noah Misch, reviewed by me and Alexey Klyukin
This commit is contained in:
Robert Haas
2011-06-21 22:15:24 -04:00
parent 771a9f69f7
commit 8f9fe6edce
11 changed files with 2401 additions and 2280 deletions
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2
src/include/parser/parse_clause.h
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@@ -44,4 +44,6 @@ extern List *transformDistinctOnClause(ParseState *pstate, List *distinctlist,
extern Index assignSortGroupRef(TargetEntry *tle, List *tlist);
extern bool targetIsInSortList(TargetEntry *tle, Oid sortop, List *sortList);
extern Node *relabel_to_typmod(Node *expr, int32 typmod);
#endif /* PARSE_CLAUSE_H */