Preserve exposed type of subquery outputs when substituting NULLs.

I thought I could get away with hardcoded int4 here, but the buildfarm
says differently.

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index ec0bf3e19f6ded15d5024da2a57d4d77705899a3..fdaa9648f25185e79803843fcd29447112e50d07 100644 (file)
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -20,7 +20,6 @@
 #include "access/sysattr.h"
 #include "catalog/pg_class.h"
 #include "catalog/pg_operator.h"
-#include "catalog/pg_type.h"
 #include "foreign/fdwapi.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
@@ -2117,6 +2116,7 @@ remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel)
    foreach(lc, subquery->targetList)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(lc);
+       Node       *texpr = (Node *) tle->expr;
 
        /*
         * If it has a sortgroupref number, it's used in some sort/group
@@ -2140,28 +2140,24 @@ remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel)
         * If it contains a set-returning function, we can't remove it since
         * that could change the number of rows returned by the subquery.
         */
-       if (expression_returns_set((Node *) tle->expr))
+       if (expression_returns_set(texpr))
            continue;
 
        /*
         * If it contains volatile functions, we daren't remove it for fear
         * that the user is expecting their side-effects to happen.
         */
-       if (contain_volatile_functions((Node *) tle->expr))
+       if (contain_volatile_functions(texpr))
            continue;
 
        /*
         * OK, we don't need it.  Replace the expression with a NULL constant.
-        * We can just make the constant be of INT4 type, since nothing's
-        * going to look at it anyway.
+        * Preserve the exposed type of the expression, in case something
+        * looks at the rowtype of the subquery's result.
         */
-       tle->expr = (Expr *) makeConst(INT4OID,
-                                      -1,
-                                      InvalidOid,
-                                      sizeof(int32),
-                                      (Datum) 0,
-                                      true,    /* isnull */
-                                      true /* byval */ );
+       tle->expr = (Expr *) makeNullConst(exprType(texpr),
+                                          exprTypmod(texpr),
+                                          exprCollation(texpr));
    }
 }