Per-column collation support

This adds collation support for columns and domains, a COLLATE clause
to override it per expression, and B-tree index support.

Peter Eisentraut
reviewed by Pavel Stehule, Itagaki Takahiro, Robert Haas, Noah Misch

src/backend/executor/nodeFunctionscan.c

@@ -24,6 +24,7 @@
 
 #include "executor/nodeFunctionscan.h"
 #include "funcapi.h"
+#include "nodes/nodeFuncs.h"
 #include "utils/builtins.h"
 
 
@@ -185,12 +186,16 @@ ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
 						   funcrettype,
 						   -1,
 						   0);
+		TupleDescInitEntryCollation(tupdesc,
+									(AttrNumber) 1,
+									exprCollation(node->funcexpr));
 	}
 	else if (functypclass == TYPEFUNC_RECORD)
 	{
 		tupdesc = BuildDescFromLists(node->funccolnames,
 									 node->funccoltypes,
-									 node->funccoltypmods);
+									 node->funccoltypmods,
+									 node->funccolcollations);
 	}
 	else
 	{