Constant expressions that appear in ORDER BY, GROUP BY, DISTINCT ON

lists should be reverse-compiled into targetlist index numbers, because
that's the only interpretation the parser allows for a constant in these
clauses.  (Ergo, the only way they could have gotten into the list in
the first place is to have come from the targetlist; so this should always
work.)  Per problem report from Peter E.

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index b9aab50f62848bea02ef48119f69279bc49e53c3..474ebdfec745102abc6ef83aa32b347749c633cc 100644 (file)
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -3,7 +3,7 @@
  *             back to source text
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.75 2001/03/22 06:16:18 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.76 2001/04/15 03:14:18 tgl Exp $
  *
  *   This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -120,6 +120,9 @@ static void get_basic_select_query(Query *query, deparse_context *context);
 static void get_setop_query(Node *setOp, Query *query,
                deparse_context *context, bool toplevel);
 static bool simple_distinct(List *distinctClause, List *targetList);
+static void get_rule_sortgroupclause(SortClause *srt, List *tlist,
+                                    bool force_colno,
+                                    deparse_context *context);
 static void get_names_for_var(Var *var, deparse_context *context,
                  char **refname, char **attname);
 static bool get_alias_for_case(CaseExpr *caseexpr, deparse_context *context,
@@ -925,7 +928,7 @@ static void
 get_select_query_def(Query *query, deparse_context *context)
 {
    StringInfo  buf = context->buf;
-   bool        shortform_orderby;
+   bool        force_colno;
    char       *sep;
    List       *l;
 
@@ -938,12 +941,12 @@ get_select_query_def(Query *query, deparse_context *context)
    {
        get_setop_query(query->setOperations, query, context, true);
        /* ORDER BY clauses must be simple in this case */
-       shortform_orderby = true;
+       force_colno = true;
    }
    else
    {
        get_basic_select_query(query, context);
-       shortform_orderby = false;
+       force_colno = false;
    }
 
    /* Add the ORDER BY clause if given */
@@ -954,16 +957,11 @@ get_select_query_def(Query *query, deparse_context *context)
        foreach(l, query->sortClause)
        {
            SortClause *srt = (SortClause *) lfirst(l);
-           TargetEntry *sorttle;
            char       *opname;
 
-           sorttle = get_sortgroupclause_tle(srt,
-                                             query->targetList);
            appendStringInfo(buf, sep);
-           if (shortform_orderby)
-               appendStringInfo(buf, "%d", sorttle->resdom->resno);
-           else
-               get_rule_expr(sorttle->expr, context);
+           get_rule_sortgroupclause(srt, query->targetList,
+                                    force_colno, context);
            opname = get_opname(srt->sortop);
            if (strcmp(opname, "<") != 0)
            {
@@ -1017,12 +1015,10 @@ get_basic_select_query(Query *query, deparse_context *context)
            foreach(l, query->distinctClause)
            {
                SortClause *srt = (SortClause *) lfirst(l);
-               Node       *sortexpr;
 
-               sortexpr = get_sortgroupclause_expr(srt,
-                                                   query->targetList);
                appendStringInfo(buf, sep);
-               get_rule_expr(sortexpr, context);
+               get_rule_sortgroupclause(srt, query->targetList,
+                                        false, context);
                sep = ", ";
            }
            appendStringInfo(buf, ")");
@@ -1082,12 +1078,10 @@ get_basic_select_query(Query *query, deparse_context *context)
        foreach(l, query->groupClause)
        {
            GroupClause *grp = (GroupClause *) lfirst(l);
-           Node       *groupexpr;
 
-           groupexpr = get_sortgroupclause_expr(grp,
-                                                query->targetList);
            appendStringInfo(buf, sep);
-           get_rule_expr(groupexpr, context);
+           get_rule_sortgroupclause(grp, query->targetList,
+                                    false, context);
            sep = ", ";
        }
    }
@@ -1182,6 +1176,32 @@ simple_distinct(List *distinctClause, List *targetList)
    return true;
 }
 
+/*
+ * Display a sort/group clause.
+ */
+static void
+get_rule_sortgroupclause(SortClause *srt, List *tlist, bool force_colno,
+                        deparse_context *context)
+{
+   StringInfo  buf = context->buf;
+   TargetEntry *tle;
+   Node       *expr;
+
+   tle = get_sortgroupclause_tle(srt, tlist);
+   expr = tle->expr;
+   /*
+    * Use column-number form if requested by caller or if expression is a
+    * constant --- a constant is ambiguous (and will be misinterpreted
+    * by findTargetlistEntry()) if we dump it explicitly.
+    */
+   if (force_colno || (expr && IsA(expr, Const)))
+   {
+       Assert(!tle->resdom->resjunk);
+       appendStringInfo(buf, "%d", tle->resdom->resno);
+   }
+   else
+       get_rule_expr(expr, context);
+}
 
 /* ----------
  * get_insert_query_def            - Parse back an INSERT parsetree