Revise collation derivation method and expression-tree representation.

All expression nodes now have an explicit output-collation field, unless
they are known to only return a noncollatable data type (such as boolean
or record).  Also, nodes that can invoke collation-aware functions store
a separate field that is the collation value to pass to the function.
This avoids confusion that arises when a function has collatable inputs
and noncollatable output type, or vice versa.

Also, replace the parser's on-the-fly collation assignment method with
a post-pass over the completed expression tree.  This allows us to use
a more complex (and hopefully more nearly spec-compliant) assignment
rule without paying for it in extra storage in every expression node.

Fix assorted bugs in the planner's handling of collations by making
collation one of the defining properties of an EquivalenceClass and
by converting CollateExprs into discardable RelabelType nodes during
expression preprocessing.

1 files changed, 6 insertions, 11 deletions

diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index a2d6c598104..a187287e283 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -78,7 +78,6 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		retset;
 	int			nvargs;
 	FuncDetailCode fdresult;
-	Oid			funccollid;
 
 	/*
 	 * Most of the rest of the parser just assumes that functions do not have
@@ -344,12 +343,6 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	/* perform the necessary typecasting of arguments */
 	make_fn_arguments(pstate, fargs, actual_arg_types, declared_arg_types);
 
-	/* XXX: If we knew which functions required collation information,
-	 * we could selectively set the last argument to true here. */
-	funccollid = select_common_collation(pstate, fargs, false);
-	if (!OidIsValid(funccollid))
-		funccollid = get_typcollation(rettype);
-
 	/*
 	 * If it's a variadic function call, transform the last nvargs arguments
 	 * into an array --- unless it's an "any" variadic.
@@ -374,6 +367,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 errmsg("could not find array type for data type %s",
 							format_type_be(newa->element_typeid)),
 				  parser_errposition(pstate, exprLocation((Node *) vargs))));
+		/* array_collid will be set by parse_collate.c */
 		newa->multidims = false;
 		newa->location = exprLocation((Node *) vargs);
 
@@ -389,8 +383,8 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		funcexpr->funcresulttype = rettype;
 		funcexpr->funcretset = retset;
 		funcexpr->funcformat = COERCE_EXPLICIT_CALL;
+		/* funccollid and inputcollid will be set by parse_collate.c */
 		funcexpr->args = fargs;
-		funcexpr->collid = funccollid;
 		funcexpr->location = location;
 
 		retval = (Node *) funcexpr;
@@ -402,9 +396,9 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 
 		aggref->aggfnoid = funcid;
 		aggref->aggtype = rettype;
+		/* aggcollid and inputcollid will be set by parse_collate.c */
 		/* args, aggorder, aggdistinct will be set by transformAggregateCall */
 		aggref->aggstar = agg_star;
-		aggref->collid = funccollid;
 		/* agglevelsup will be set by transformAggregateCall */
 		aggref->location = location;
 
@@ -458,11 +452,11 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 
 		wfunc->winfnoid = funcid;
 		wfunc->wintype = rettype;
+		/* wincollid and inputcollid will be set by parse_collate.c */
 		wfunc->args = fargs;
 		/* winref will be set by transformWindowFuncCall */
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
-		wfunc->collid = funccollid;
 		wfunc->location = location;
 
 		/*
@@ -1390,7 +1384,8 @@ ParseComplexProjection(ParseState *pstate, char *funcname, Node *first_arg,
 			fselect->fieldnum = i + 1;
 			fselect->resulttype = att->atttypid;
 			fselect->resulttypmod = att->atttypmod;
-			fselect->resultcollation = att->attcollation;
+			/* resultcollid may get overridden by parse_collate.c */
+			fselect->resultcollid = att->attcollation;
 			return (Node *) fselect;
 		}
 	}