1 files changed, 131 insertions, 1 deletions

diff --git a/src/backend/parser/parse_coerce.c b/src/backend/parser/parse_coerce.c
index 5b0dc1420d0..2fd808d26b2 100644
--- a/src/backend/parser/parse_coerce.c
+++ b/src/backend/parser/parse_coerce.c
@@ -16,6 +16,7 @@
 
 #include "catalog/pg_cast.h"
 #include "catalog/pg_class.h"
+#include "catalog/pg_collation.h"
 #include "catalog/pg_inherits_fn.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
@@ -216,6 +217,7 @@ coerce_type(ParseState *pstate, Node *node,
 
 		newcon->consttype = baseTypeId;
 		newcon->consttypmod = inputTypeMod;
+		newcon->constcollid = get_typcollation(newcon->consttype);
 		newcon->constlen = typeLen(targetType);
 		newcon->constbyval = typeByVal(targetType);
 		newcon->constisnull = con->constisnull;
@@ -277,6 +279,14 @@ coerce_type(ParseState *pstate, Node *node,
 		if (result)
 			return result;
 	}
+	if (IsA(node, CollateClause))
+	{
+		CollateClause *cc = (CollateClause *) node;
+
+		cc->arg = (Expr *) coerce_type(pstate, (Node *) cc->arg, inputTypeId, targetTypeId, targetTypeMod,
+									   ccontext, cformat, location);
+		return (Node *) cc;
+	}
 	pathtype = find_coercion_pathway(targetTypeId, inputTypeId, ccontext,
 									 &funcId);
 	if (pathtype != COERCION_PATH_NONE)
@@ -718,6 +728,7 @@ build_coercion_expression(Node *node,
 		FuncExpr   *fexpr;
 		List	   *args;
 		Const	   *cons;
+		Oid			collation;
 
 		Assert(OidIsValid(funcId));
 
@@ -749,7 +760,9 @@ build_coercion_expression(Node *node,
 			args = lappend(args, cons);
 		}
 
-		fexpr = makeFuncExpr(funcId, targetTypeId, args, cformat);
+		collation = coercion_expression_result_collation(targetTypeId, node);
+
+		fexpr = makeFuncExpr(funcId, targetTypeId, args, collation, cformat);
 		fexpr->location = location;
 		return (Node *) fexpr;
 	}
@@ -2081,3 +2094,120 @@ typeIsOfTypedTable(Oid reltypeId, Oid reloftypeId)
 
 	return result;
 }
+
+
+/*
+ * select_common_collation() -- determine one collation to apply for
+ * an expression node, for evaluating the expression itself or to
+ * label the result of the expression node.
+ *
+ * none_ok means that it is permitted to return "no" collation.  It is
+ * then not possible to sort the result value of whatever expression
+ * is applying this.  none_ok = true reflects the rules of SQL
+ * standard clause "Result of data type combinations", none_ok = false
+ * reflects the rules of clause "Collation determination" (in some
+ * cases invoked via "Grouping operations").
+ */
+Oid
+select_common_collation(ParseState *pstate, List *exprs, bool none_ok)
+{
+	ListCell   *lc;
+
+	/*
+	 * Check if there are any explicit collation derivations.  If so,
+	 * they must all be the same.
+	 */
+	foreach(lc, exprs)
+	{
+		Node	   *pexpr = (Node *) lfirst(lc);
+		Oid			pcoll = exprCollation(pexpr);
+		bool		pexplicit = IsA(pexpr, CollateClause);
+
+		if (pcoll && pexplicit)
+		{
+			ListCell	*lc2;
+			for_each_cell(lc2, lnext(lc))
+			{
+				Node	   *nexpr = (Node *) lfirst(lc2);
+				Oid			ncoll = exprCollation(nexpr);
+				bool		nexplicit = IsA(nexpr, CollateClause);
+
+				if (!ncoll || !nexplicit)
+					continue;
+
+				if (ncoll != pcoll)
+					ereport(ERROR,
+							(errcode(ERRCODE_COLLATION_MISMATCH),
+							 errmsg("collation mismatch between explicit collations \"%s\" and \"%s\"",
+									get_collation_name(pcoll),
+									get_collation_name(ncoll)),
+							 parser_errposition(pstate, exprLocation(nexpr))));
+			}
+
+			return pcoll;
+		}
+	}
+
+	/*
+	 * Check if there are any implicit collation derivations.
+	 */
+	foreach(lc, exprs)
+	{
+		Node	   *pexpr = (Node *) lfirst(lc);
+		Oid			pcoll = exprCollation(pexpr);
+
+		if (pcoll && pcoll != DEFAULT_COLLATION_OID)
+		{
+			ListCell	*lc2;
+			for_each_cell(lc2, lnext(lc))
+			{
+				Node	   *nexpr = (Node *) lfirst(lc2);
+				Oid			ncoll = exprCollation(nexpr);
+
+				if (!ncoll || ncoll == DEFAULT_COLLATION_OID)
+					continue;
+
+				if (ncoll != pcoll)
+				{
+					if (none_ok)
+						return InvalidOid;
+					ereport(ERROR,
+							(errcode(ERRCODE_COLLATION_MISMATCH),
+							 errmsg("collation mismatch between implicit collations \"%s\" and \"%s\"",
+									get_collation_name(pcoll),
+									get_collation_name(ncoll)),
+							 errhint("You can override the collation by applying the COLLATE clause to one or both expressions."),
+							 parser_errposition(pstate, exprLocation(nexpr))));
+				}
+			}
+
+			return pcoll;
+		}
+	}
+
+	foreach(lc, exprs)
+	{
+		Node	   *pexpr = (Node *) lfirst(lc);
+		Oid			pcoll = exprCollation(pexpr);
+
+		if (pcoll == DEFAULT_COLLATION_OID)
+		{
+			ListCell	*lc2;
+			for_each_cell(lc2, lnext(lc))
+			{
+				Node	   *nexpr = (Node *) lfirst(lc2);
+				Oid			ncoll = exprCollation(nexpr);
+
+				if (ncoll != pcoll)
+					break;
+			}
+
+			return pcoll;
+		}
+	}
+
+	/*
+	 * Else use default
+	 */
+	return InvalidOid;
+}