Re: BUG #18589: pg_get_viewdef returns wrong query - Mailing list pgsql-bugs

I wrote:
> Yeah, I was uncertain whether to bother with that detail.  It's true
> that there's no bug in GROUP BY because the parser prefers SQL99
> semantics in that case, but maybe we shouldn't have this code assuming
> that?  And it wasn't easy to do with the special_exprkind approach.
> But it is pretty easy with the two-bools approach, so I fixed that in
> the attached v2.

I was just about to commit v2 when I realized that it's wrong, because
what we need to be checking against is the output column name(s) that
get_target_list() will print, and that's not necessarily tle->resname.
You can in fact make v2 misbehave with ALTER VIEW RENAME COLUMN, as
shown by the added test cases in attached v3.

That complicates matters greatly because it means that we also need
access to the current get_query_def call's resultDesc.  To avoid
cluttering things impossibly, I decided that resultDesc ought to be
passed down in the deparse_context not as a separate parameter, and
while doing that it seemed better to do the same with colNamesVisible.
(There is one place that has to save-n-restore colNamesVisible to
make that work, but overall it's less code and clutter.)

It's slightly annoying that there are now three places that know
how get_target_list chooses output column names.  I thought about
refactoring to get that down to one place, but couldn't really
find anything that didn't net out as more code and ugliness.

Also, while looking at this I realized that get_select_query_def's
habit of saving-and-restoring windowClause and windowTList is
completely pointless: it has only one caller and that one has
just set up a fresh deparse_context, which won't be used anymore
afterwards.  If there were a code path in which that did something,
the lack of save-and-restore logic in get_update_query_def and
friends would likely be a bug.  So I just dropped it.  I believe
that it's not really necessary to save-n-restore inGroupBy or
varInOrderBy either (rather than just reset them to false).
But those cases aren't quite as clear-cut, and resetting to false
isn't much cheaper than restoring a saved value, so I left those
bits as-is.

            regards, tom lane

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 00eda1b34c..b31be31321 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -50,7 +50,6 @@
 #include "optimizer/optimizer.h"
 #include "parser/parse_agg.h"
 #include "parser/parse_func.h"
-#include "parser/parse_node.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parser.h"
@@ -114,14 +113,16 @@ typedef struct
 {
     StringInfo    buf;            /* output buffer to append to */
     List       *namespaces;        /* List of deparse_namespace nodes */
+    TupleDesc    resultDesc;        /* if top level of a view, the view's tupdesc */
+    List       *targetList;        /* Current query level's SELECT targetlist */
     List       *windowClause;    /* Current query level's WINDOW clause */
-    List       *windowTList;    /* targetlist for resolving WINDOW clause */
     int            prettyFlags;    /* enabling of pretty-print functions */
     int            wrapColumn;        /* max line length, or -1 for no limit */
     int            indentLevel;    /* current indent level for pretty-print */
     bool        varprefix;        /* true to print prefixes on Vars */
-    ParseExprKind special_exprkind; /* set only for exprkinds needing special
-                                     * handling */
+    bool        colNamesVisible;    /* do we care about output column names? */
+    bool        inGroupBy;        /* deparsing GROUP BY clause? */
+    bool        varInOrderBy;    /* deparsing simple Var in ORDER BY? */
     Bitmapset  *appendparents;    /* if not null, map child Vars of these relids
                                  * back to the parent rel */
 } deparse_context;
@@ -398,27 +399,19 @@ static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
                           int prettyFlags, int wrapColumn, int startIndent);
 static void get_values_def(List *values_lists, deparse_context *context);
 static void get_with_clause(Query *query, deparse_context *context);
-static void get_select_query_def(Query *query, deparse_context *context,
-                                 TupleDesc resultDesc, bool colNamesVisible);
-static void get_insert_query_def(Query *query, deparse_context *context,
-                                 bool colNamesVisible);
-static void get_update_query_def(Query *query, deparse_context *context,
-                                 bool colNamesVisible);
+static void get_select_query_def(Query *query, deparse_context *context);
+static void get_insert_query_def(Query *query, deparse_context *context);
+static void get_update_query_def(Query *query, deparse_context *context);
 static void get_update_query_targetlist_def(Query *query, List *targetList,
                                             deparse_context *context,
                                             RangeTblEntry *rte);
-static void get_delete_query_def(Query *query, deparse_context *context,
-                                 bool colNamesVisible);
-static void get_merge_query_def(Query *query, deparse_context *context,
-                                bool colNamesVisible);
+static void get_delete_query_def(Query *query, deparse_context *context);
+static void get_merge_query_def(Query *query, deparse_context *context);
 static void get_utility_query_def(Query *query, deparse_context *context);
-static void get_basic_select_query(Query *query, deparse_context *context,
-                                   TupleDesc resultDesc, bool colNamesVisible);
-static void get_target_list(List *targetList, deparse_context *context,
-                            TupleDesc resultDesc, bool colNamesVisible);
+static void get_basic_select_query(Query *query, deparse_context *context);
+static void get_target_list(List *targetList, deparse_context *context);
 static void get_setop_query(Node *setOp, Query *query,
-                            deparse_context *context,
-                            TupleDesc resultDesc, bool colNamesVisible);
+                            deparse_context *context);
 static Node *get_rule_sortgroupclause(Index ref, List *tlist,
                                       bool force_colno,
                                       deparse_context *context);
@@ -515,7 +508,7 @@ static char *generate_qualified_relation_name(Oid relid);
 static char *generate_function_name(Oid funcid, int nargs,
                                     List *argnames, Oid *argtypes,
                                     bool has_variadic, bool *use_variadic_p,
-                                    ParseExprKind special_exprkind);
+                                    bool inGroupBy);
 static char *generate_operator_name(Oid operid, Oid arg1, Oid arg2);
 static void add_cast_to(StringInfo buf, Oid typid);
 static char *generate_qualified_type_name(Oid typid);
@@ -1094,13 +1087,16 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
         /* Set up context with one-deep namespace stack */
         context.buf = &buf;
         context.namespaces = list_make1(&dpns);
+        context.resultDesc = NULL;
+        context.targetList = NIL;
         context.windowClause = NIL;
-        context.windowTList = NIL;
         context.varprefix = true;
         context.prettyFlags = GET_PRETTY_FLAGS(pretty);
         context.wrapColumn = WRAP_COLUMN_DEFAULT;
         context.indentLevel = PRETTYINDENT_STD;
-        context.special_exprkind = EXPR_KIND_NONE;
+        context.colNamesVisible = true;
+        context.inGroupBy = false;
+        context.varInOrderBy = false;
         context.appendparents = NULL;

         get_rule_expr(qual, &context, false);
@@ -1111,7 +1107,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
     appendStringInfo(&buf, "EXECUTE FUNCTION %s(",
                      generate_function_name(trigrec->tgfoid, 0,
                                             NIL, NULL,
-                                            false, NULL, EXPR_KIND_NONE));
+                                            false, NULL, false));

     if (trigrec->tgnargs > 0)
     {
@@ -2992,7 +2988,7 @@ pg_get_functiondef(PG_FUNCTION_ARGS)
         appendStringInfo(&buf, " SUPPORT %s",
                          generate_function_name(proc->prosupport, 1,
                                                 NIL, argtypes,
-                                                false, NULL, EXPR_KIND_NONE));
+                                                false, NULL, false));
     }

     if (oldlen != buf.len)
@@ -3632,13 +3628,16 @@ deparse_expression_pretty(Node *expr, List *dpcontext,
     initStringInfo(&buf);
     context.buf = &buf;
     context.namespaces = dpcontext;
+    context.resultDesc = NULL;
+    context.targetList = NIL;
     context.windowClause = NIL;
-    context.windowTList = NIL;
     context.varprefix = forceprefix;
     context.prettyFlags = prettyFlags;
     context.wrapColumn = WRAP_COLUMN_DEFAULT;
     context.indentLevel = startIndent;
-    context.special_exprkind = EXPR_KIND_NONE;
+    context.colNamesVisible = true;
+    context.inGroupBy = false;
+    context.varInOrderBy = false;
     context.appendparents = NULL;

     get_rule_expr(expr, &context, showimplicit);
@@ -5283,13 +5282,16 @@ make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,

         context.buf = buf;
         context.namespaces = list_make1(&dpns);
+        context.resultDesc = NULL;
+        context.targetList = NIL;
         context.windowClause = NIL;
-        context.windowTList = NIL;
         context.varprefix = (list_length(query->rtable) != 1);
         context.prettyFlags = prettyFlags;
         context.wrapColumn = WRAP_COLUMN_DEFAULT;
         context.indentLevel = PRETTYINDENT_STD;
-        context.special_exprkind = EXPR_KIND_NONE;
+        context.colNamesVisible = true;
+        context.inGroupBy = false;
+        context.varInOrderBy = false;
         context.appendparents = NULL;

         set_deparse_for_query(&dpns, query, NIL);
@@ -5451,14 +5453,17 @@ get_query_def(Query *query, StringInfo buf, List *parentnamespace,

     context.buf = buf;
     context.namespaces = lcons(&dpns, list_copy(parentnamespace));
+    context.resultDesc = NULL;
+    context.targetList = NIL;
     context.windowClause = NIL;
-    context.windowTList = NIL;
     context.varprefix = (parentnamespace != NIL ||
                          list_length(query->rtable) != 1);
     context.prettyFlags = prettyFlags;
     context.wrapColumn = wrapColumn;
     context.indentLevel = startIndent;
-    context.special_exprkind = EXPR_KIND_NONE;
+    context.colNamesVisible = colNamesVisible;
+    context.inGroupBy = false;
+    context.varInOrderBy = false;
     context.appendparents = NULL;

     set_deparse_for_query(&dpns, query, parentnamespace);
@@ -5466,23 +5471,25 @@ get_query_def(Query *query, StringInfo buf, List *parentnamespace,
     switch (query->commandType)
     {
         case CMD_SELECT:
-            get_select_query_def(query, &context, resultDesc, colNamesVisible);
+            /* We set context.resultDesc only if it's a SELECT */
+            context.resultDesc = resultDesc;
+            get_select_query_def(query, &context);
             break;

         case CMD_UPDATE:
-            get_update_query_def(query, &context, colNamesVisible);
+            get_update_query_def(query, &context);
             break;

         case CMD_INSERT:
-            get_insert_query_def(query, &context, colNamesVisible);
+            get_insert_query_def(query, &context);
             break;

         case CMD_DELETE:
-            get_delete_query_def(query, &context, colNamesVisible);
+            get_delete_query_def(query, &context);
             break;

         case CMD_MERGE:
-            get_merge_query_def(query, &context, colNamesVisible);
+            get_merge_query_def(query, &context);
             break;

         case CMD_NOTHING:
@@ -5687,23 +5694,18 @@ get_with_clause(Query *query, deparse_context *context)
  * ----------
  */
 static void
-get_select_query_def(Query *query, deparse_context *context,
-                     TupleDesc resultDesc, bool colNamesVisible)
+get_select_query_def(Query *query, deparse_context *context)
 {
     StringInfo    buf = context->buf;
-    List       *save_windowclause;
-    List       *save_windowtlist;
     bool        force_colno;
     ListCell   *l;

     /* Insert the WITH clause if given */
     get_with_clause(query, context);

-    /* Set up context for possible window functions */
-    save_windowclause = context->windowClause;
+    /* Subroutines may need to consult the SELECT targetlist and windowClause */
+    context->targetList = query->targetList;
     context->windowClause = query->windowClause;
-    save_windowtlist = context->windowTList;
-    context->windowTList = query->targetList;

     /*
      * If the Query node has a setOperations tree, then it's the top level of
@@ -5712,14 +5714,13 @@ get_select_query_def(Query *query, deparse_context *context,
      */
     if (query->setOperations)
     {
-        get_setop_query(query->setOperations, query, context, resultDesc,
-                        colNamesVisible);
+        get_setop_query(query->setOperations, query, context);
         /* ORDER BY clauses must be simple in this case */
         force_colno = true;
     }
     else
     {
-        get_basic_select_query(query, context, resultDesc, colNamesVisible);
+        get_basic_select_query(query, context);
         force_colno = false;
     }

@@ -5808,9 +5809,6 @@ get_select_query_def(Query *query, deparse_context *context,
                 appendStringInfoString(buf, " SKIP LOCKED");
         }
     }
-
-    context->windowClause = save_windowclause;
-    context->windowTList = save_windowtlist;
 }

 /*
@@ -5888,8 +5886,7 @@ get_simple_values_rte(Query *query, TupleDesc resultDesc)
 }

 static void
-get_basic_select_query(Query *query, deparse_context *context,
-                       TupleDesc resultDesc, bool colNamesVisible)
+get_basic_select_query(Query *query, deparse_context *context)
 {
     StringInfo    buf = context->buf;
     RangeTblEntry *values_rte;
@@ -5907,7 +5904,7 @@ get_basic_select_query(Query *query, deparse_context *context,
      * VALUES part.  This reverses what transformValuesClause() did at parse
      * time.
      */
-    values_rte = get_simple_values_rte(query, resultDesc);
+    values_rte = get_simple_values_rte(query, context->resultDesc);
     if (values_rte)
     {
         get_values_def(values_rte->values_lists, context);
@@ -5945,7 +5942,7 @@ get_basic_select_query(Query *query, deparse_context *context,
     }

     /* Then we tell what to select (the targetlist) */
-    get_target_list(query->targetList, context, resultDesc, colNamesVisible);
+    get_target_list(query->targetList, context);

     /* Add the FROM clause if needed */
     get_from_clause(query, " FROM ", context);
@@ -5961,15 +5958,15 @@ get_basic_select_query(Query *query, deparse_context *context,
     /* Add the GROUP BY clause if given */
     if (query->groupClause != NULL || query->groupingSets != NULL)
     {
-        ParseExprKind save_exprkind;
+        bool        save_ingroupby;

         appendContextKeyword(context, " GROUP BY ",
                              -PRETTYINDENT_STD, PRETTYINDENT_STD, 1);
         if (query->groupDistinct)
             appendStringInfoString(buf, "DISTINCT ");

-        save_exprkind = context->special_exprkind;
-        context->special_exprkind = EXPR_KIND_GROUP_BY;
+        save_ingroupby = context->inGroupBy;
+        context->inGroupBy = true;

         if (query->groupingSets == NIL)
         {
@@ -5997,7 +5994,7 @@ get_basic_select_query(Query *query, deparse_context *context,
             }
         }

-        context->special_exprkind = save_exprkind;
+        context->inGroupBy = save_ingroupby;
     }

     /* Add the HAVING clause if given */
@@ -6017,13 +6014,10 @@ get_basic_select_query(Query *query, deparse_context *context,
  * get_target_list            - Parse back a SELECT target list
  *
  * This is also used for RETURNING lists in INSERT/UPDATE/DELETE/MERGE.
- *
- * resultDesc and colNamesVisible are as for get_query_def()
  * ----------
  */
 static void
-get_target_list(List *targetList, deparse_context *context,
-                TupleDesc resultDesc, bool colNamesVisible)
+get_target_list(List *targetList, deparse_context *context)
 {
     StringInfo    buf = context->buf;
     StringInfoData targetbuf;
@@ -6080,7 +6074,7 @@ get_target_list(List *targetList, deparse_context *context,
              * assigned column name explicitly.  Otherwise, show it only if
              * it's not FigureColname's fallback.
              */
-            attname = colNamesVisible ? NULL : "?column?";
+            attname = context->colNamesVisible ? NULL : "?column?";
         }

         /*
@@ -6089,8 +6083,9 @@ get_target_list(List *targetList, deparse_context *context,
          * effects of any column RENAME that's been done on the view).
          * Otherwise, just use what we can find in the TLE.
          */
-        if (resultDesc && colno <= resultDesc->natts)
-            colname = NameStr(TupleDescAttr(resultDesc, colno - 1)->attname);
+        if (context->resultDesc && colno <= context->resultDesc->natts)
+            colname = NameStr(TupleDescAttr(context->resultDesc,
+                                            colno - 1)->attname);
         else
             colname = tle->resname;

@@ -6158,8 +6153,7 @@ get_target_list(List *targetList, deparse_context *context,
 }

 static void
-get_setop_query(Node *setOp, Query *query, deparse_context *context,
-                TupleDesc resultDesc, bool colNamesVisible)
+get_setop_query(Node *setOp, Query *query, deparse_context *context)
 {
     StringInfo    buf = context->buf;
     bool        need_paren;
@@ -6184,8 +6178,8 @@ get_setop_query(Node *setOp, Query *query, deparse_context *context,
                       subquery->limitCount);
         if (need_paren)
             appendStringInfoChar(buf, '(');
-        get_query_def(subquery, buf, context->namespaces, resultDesc,
-                      colNamesVisible,
+        get_query_def(subquery, buf, context->namespaces,
+                      context->resultDesc, context->colNamesVisible,
                       context->prettyFlags, context->wrapColumn,
                       context->indentLevel);
         if (need_paren)
@@ -6195,6 +6189,7 @@ get_setop_query(Node *setOp, Query *query, deparse_context *context,
     {
         SetOperationStmt *op = (SetOperationStmt *) setOp;
         int            subindent;
+        bool        save_colnamesvisible;

         /*
          * We force parens when nesting two SetOperationStmts, except when the
@@ -6228,7 +6223,7 @@ get_setop_query(Node *setOp, Query *query, deparse_context *context,
         else
             subindent = 0;

-        get_setop_query(op->larg, query, context, resultDesc, colNamesVisible);
+        get_setop_query(op->larg, query, context);

         if (need_paren)
             appendContextKeyword(context, ") ", -subindent, 0, 0);
@@ -6272,7 +6267,15 @@ get_setop_query(Node *setOp, Query *query, deparse_context *context,
             subindent = 0;
         appendContextKeyword(context, "", subindent, 0, 0);

-        get_setop_query(op->rarg, query, context, resultDesc, false);
+        /*
+         * The output column names of the RHS sub-select don't matter.
+         */
+        save_colnamesvisible = context->colNamesVisible;
+        context->colNamesVisible = false;
+
+        get_setop_query(op->rarg, query, context);
+
+        context->colNamesVisible = save_colnamesvisible;

         if (PRETTY_INDENT(context))
             context->indentLevel -= subindent;
@@ -6306,20 +6309,32 @@ get_rule_sortgroupclause(Index ref, List *tlist, bool force_colno,
      * Use column-number form if requested by caller.  Otherwise, if
      * expression is a constant, force it to be dumped with an explicit cast
      * as decoration --- this is because a simple integer constant is
-     * ambiguous (and will be misinterpreted by findTargetlistEntry()) if we
-     * dump it without any decoration.  If it's anything more complex than a
-     * simple Var, then force extra parens around it, to ensure it can't be
-     * misinterpreted as a cube() or rollup() construct.
+     * ambiguous (and will be misinterpreted by findTargetlistEntrySQL92()) if
+     * we dump it without any decoration.  Similarly, if it's just a Var,
+     * there is risk of misinterpretation if the column name is reassigned in
+     * the SELECT list, so we may need to force table qualification.  And, if
+     * it's anything more complex than a simple Var, then force extra parens
+     * around it, to ensure it can't be misinterpreted as a cube() or rollup()
+     * construct.
      */
     if (force_colno)
     {
         Assert(!tle->resjunk);
         appendStringInfo(buf, "%d", tle->resno);
     }
-    else if (expr && IsA(expr, Const))
+    else if (!expr)
+         /* do nothing, probably can't happen */ ;
+    else if (IsA(expr, Const))
         get_const_expr((Const *) expr, context, 1);
-    else if (!expr || IsA(expr, Var))
-        get_rule_expr(expr, context, true);
+    else if (IsA(expr, Var))
+    {
+        /* Tell get_variable to check for name conflict */
+        bool        save_varinorderby = context->varInOrderBy;
+
+        context->varInOrderBy = true;
+        (void) get_variable((Var *) expr, 0, false, context);
+        context->varInOrderBy = save_varinorderby;
+    }
     else
     {
         /*
@@ -6608,8 +6623,7 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
  * ----------
  */
 static void
-get_insert_query_def(Query *query, deparse_context *context,
-                     bool colNamesVisible)
+get_insert_query_def(Query *query, deparse_context *context)
 {
     StringInfo    buf = context->buf;
     RangeTblEntry *select_rte = NULL;
@@ -6815,7 +6829,7 @@ get_insert_query_def(Query *query, deparse_context *context,
     {
         appendContextKeyword(context, " RETURNING",
                              -PRETTYINDENT_STD, PRETTYINDENT_STD, 1);
-        get_target_list(query->returningList, context, NULL, colNamesVisible);
+        get_target_list(query->returningList, context);
     }
 }

@@ -6825,8 +6839,7 @@ get_insert_query_def(Query *query, deparse_context *context,
  * ----------
  */
 static void
-get_update_query_def(Query *query, deparse_context *context,
-                     bool colNamesVisible)
+get_update_query_def(Query *query, deparse_context *context)
 {
     StringInfo    buf = context->buf;
     RangeTblEntry *rte;
@@ -6872,7 +6885,7 @@ get_update_query_def(Query *query, deparse_context *context,
     {
         appendContextKeyword(context, " RETURNING",
                              -PRETTYINDENT_STD, PRETTYINDENT_STD, 1);
-        get_target_list(query->returningList, context, NULL, colNamesVisible);
+        get_target_list(query->returningList, context);
     }
 }

@@ -7034,8 +7047,7 @@ get_update_query_targetlist_def(Query *query, List *targetList,
  * ----------
  */
 static void
-get_delete_query_def(Query *query, deparse_context *context,
-                     bool colNamesVisible)
+get_delete_query_def(Query *query, deparse_context *context)
 {
     StringInfo    buf = context->buf;
     RangeTblEntry *rte;
@@ -7076,7 +7088,7 @@ get_delete_query_def(Query *query, deparse_context *context,
     {
         appendContextKeyword(context, " RETURNING",
                              -PRETTYINDENT_STD, PRETTYINDENT_STD, 1);
-        get_target_list(query->returningList, context, NULL, colNamesVisible);
+        get_target_list(query->returningList, context);
     }
 }

@@ -7086,8 +7098,7 @@ get_delete_query_def(Query *query, deparse_context *context,
  * ----------
  */
 static void
-get_merge_query_def(Query *query, deparse_context *context,
-                    bool colNamesVisible)
+get_merge_query_def(Query *query, deparse_context *context)
 {
     StringInfo    buf = context->buf;
     RangeTblEntry *rte;
@@ -7240,7 +7251,7 @@ get_merge_query_def(Query *query, deparse_context *context,
     {
         appendContextKeyword(context, " RETURNING",
                              -PRETTYINDENT_STD, PRETTYINDENT_STD, 1);
-        get_target_list(query->returningList, context, NULL, colNamesVisible);
+        get_target_list(query->returningList, context);
     }
 }

@@ -7307,6 +7318,7 @@ get_variable(Var *var, int levelsup, bool istoplevel, deparse_context *context)
     deparse_columns *colinfo;
     char       *refname;
     char       *attname;
+    bool        need_prefix;

     /* Find appropriate nesting depth */
     netlevelsup = var->varlevelsup + levelsup;
@@ -7502,7 +7514,45 @@ get_variable(Var *var, int levelsup, bool istoplevel, deparse_context *context)
         attname = get_rte_attribute_name(rte, attnum);
     }

-    if (refname && (context->varprefix || attname == NULL))
+    need_prefix = (context->varprefix || attname == NULL);
+
+    /*
+     * If we're considering a plain Var in an ORDER BY (but not GROUP BY)
+     * clause, we may need to add a table-name prefix to prevent
+     * findTargetlistEntrySQL92 from misinterpreting the name as an
+     * output-column name.  To avoid cluttering the output with unnecessary
+     * prefixes, do so only if there is a name match to a SELECT tlist item
+     * that is different from the Var.
+     */
+    if (context->varInOrderBy && !context->inGroupBy && !need_prefix)
+    {
+        int            colno = 0;
+
+        foreach_node(TargetEntry, tle, context->targetList)
+        {
+            char       *colname;
+
+            if (tle->resjunk)
+                continue;        /* ignore junk entries */
+            colno++;
+
+            /* This must match colname-choosing logic in get_target_list() */
+            if (context->resultDesc && colno <= context->resultDesc->natts)
+                colname = NameStr(TupleDescAttr(context->resultDesc,
+                                                colno - 1)->attname);
+            else
+                colname = tle->resname;
+
+            if (colname && strcmp(colname, attname) == 0 &&
+                !equal(var, tle->expr))
+            {
+                need_prefix = true;
+                break;
+            }
+        }
+    }
+
+    if (refname && need_prefix)
     {
         appendStringInfoString(buf, quote_identifier(refname));
         appendStringInfoChar(buf, '.');
@@ -10463,7 +10513,7 @@ get_func_expr(FuncExpr *expr, deparse_context *context,
                                             argnames, argtypes,
                                             expr->funcvariadic,
                                             &use_variadic,
-                                            context->special_exprkind));
+                                            context->inGroupBy));
     nargs = 0;
     foreach(l, expr->args)
     {
@@ -10533,7 +10583,7 @@ get_agg_expr_helper(Aggref *aggref, deparse_context *context,
         funcname = generate_function_name(aggref->aggfnoid, nargs, NIL,
                                           argtypes, aggref->aggvariadic,
                                           &use_variadic,
-                                          context->special_exprkind);
+                                          context->inGroupBy);

     /* Print the aggregate name, schema-qualified if needed */
     appendStringInfo(buf, "%s(%s", funcname,
@@ -10674,7 +10724,7 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
     if (!funcname)
         funcname = generate_function_name(wfunc->winfnoid, nargs, argnames,
                                           argtypes, false, NULL,
-                                          context->special_exprkind);
+                                          context->inGroupBy);

     appendStringInfo(buf, "%s(", funcname);

@@ -10713,7 +10763,7 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
             if (wc->name)
                 appendStringInfoString(buf, quote_identifier(wc->name));
             else
-                get_rule_windowspec(wc, context->windowTList, context);
+                get_rule_windowspec(wc, context->targetList, context);
             break;
         }
     }
@@ -12420,7 +12470,7 @@ get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
     appendStringInfo(buf, " TABLESAMPLE %s (",
                      generate_function_name(tablesample->tsmhandler, 1,
                                             NIL, argtypes,
-                                            false, NULL, EXPR_KIND_NONE));
+                                            false, NULL, false));

     nargs = 0;
     foreach(l, tablesample->args)
@@ -12840,12 +12890,14 @@ generate_qualified_relation_name(Oid relid)
  * the output.  For non-FuncExpr cases, has_variadic should be false and
  * use_variadic_p can be NULL.
  *
+ * inGroupBy must be true if we're deparsing a GROUP BY clause.
+ *
  * The result includes all necessary quoting and schema-prefixing.
  */
 static char *
 generate_function_name(Oid funcid, int nargs, List *argnames, Oid *argtypes,
                        bool has_variadic, bool *use_variadic_p,
-                       ParseExprKind special_exprkind)
+                       bool inGroupBy)
 {
     char       *result;
     HeapTuple    proctup;
@@ -12870,9 +12922,9 @@ generate_function_name(Oid funcid, int nargs, List *argnames, Oid *argtypes,

     /*
      * Due to parser hacks to avoid needing to reserve CUBE, we need to force
-     * qualification in some special cases.
+     * qualification of some function names within GROUP BY.
      */
-    if (special_exprkind == EXPR_KIND_GROUP_BY)
+    if (inGroupBy)
     {
         if (strcmp(proname, "cube") == 0 || strcmp(proname, "rollup") == 0)
             force_qualify = true;
diff --git a/src/test/regress/expected/create_view.out b/src/test/regress/expected/create_view.out
index f3f8c7b5a2..f551624afb 100644
--- a/src/test/regress/expected/create_view.out
+++ b/src/test/regress/expected/create_view.out
@@ -824,6 +824,54 @@ View definition:
            FROM temp_view_test.tx1 tx1_1
           WHERE tx1.y1 = tx1_1.f1));

+-- Test correct deparsing of ORDER BY when there is an output name conflict
+create view aliased_order_by as
+select x1 as x2, x2 as x1, x3 from tt1
+  order by x2;  -- this is interpreted per SQL92, so really ordering by x1
+\d+ aliased_order_by
+                   View "testviewschm2.aliased_order_by"
+ Column |  Type   | Collation | Nullable | Default | Storage  | Description
+--------+---------+-----------+----------+---------+----------+-------------
+ x2     | integer |           |          |         | plain    |
+ x1     | integer |           |          |         | plain    |
+ x3     | text    |           |          |         | extended |
+View definition:
+ SELECT x1 AS x2,
+    x2 AS x1,
+    x3
+   FROM tt1
+  ORDER BY tt1.x1;
+
+alter view aliased_order_by rename column x1 to x0;
+\d+ aliased_order_by
+                   View "testviewschm2.aliased_order_by"
+ Column |  Type   | Collation | Nullable | Default | Storage  | Description
+--------+---------+-----------+----------+---------+----------+-------------
+ x2     | integer |           |          |         | plain    |
+ x0     | integer |           |          |         | plain    |
+ x3     | text    |           |          |         | extended |
+View definition:
+ SELECT x1 AS x2,
+    x2 AS x0,
+    x3
+   FROM tt1
+  ORDER BY x1;
+
+alter view aliased_order_by rename column x3 to x1;
+\d+ aliased_order_by
+                   View "testviewschm2.aliased_order_by"
+ Column |  Type   | Collation | Nullable | Default | Storage  | Description
+--------+---------+-----------+----------+---------+----------+-------------
+ x2     | integer |           |          |         | plain    |
+ x0     | integer |           |          |         | plain    |
+ x1     | text    |           |          |         | extended |
+View definition:
+ SELECT x1 AS x2,
+    x2 AS x0,
+    x3 AS x1
+   FROM tt1
+  ORDER BY tt1.x1;
+
 -- Test aliasing of joins
 create view view_of_joins as
 select * from
@@ -2248,7 +2296,7 @@ drop cascades to view aliased_view_2
 drop cascades to view aliased_view_3
 drop cascades to view aliased_view_4
 DROP SCHEMA testviewschm2 CASCADE;
-NOTICE:  drop cascades to 79 other objects
+NOTICE:  drop cascades to 80 other objects
 DETAIL:  drop cascades to table t1
 drop cascades to view temporal1
 drop cascades to view temporal2
@@ -2275,6 +2323,7 @@ drop cascades to view mysecview9
 drop cascades to view unspecified_types
 drop cascades to table tt1
 drop cascades to table tx1
+drop cascades to view aliased_order_by
 drop cascades to view view_of_joins
 drop cascades to table tbl1a
 drop cascades to view view_of_joins_2a
diff --git a/src/test/regress/sql/create_view.sql b/src/test/regress/sql/create_view.sql
index 3a78be1b0c..ae6841308b 100644
--- a/src/test/regress/sql/create_view.sql
+++ b/src/test/regress/sql/create_view.sql
@@ -373,6 +373,22 @@ ALTER TABLE tmp1 RENAME TO tx1;
 \d+ aliased_view_3
 \d+ aliased_view_4

+-- Test correct deparsing of ORDER BY when there is an output name conflict
+
+create view aliased_order_by as
+select x1 as x2, x2 as x1, x3 from tt1
+  order by x2;  -- this is interpreted per SQL92, so really ordering by x1
+
+\d+ aliased_order_by
+
+alter view aliased_order_by rename column x1 to x0;
+
+\d+ aliased_order_by
+
+alter view aliased_order_by rename column x3 to x1;
+
+\d+ aliased_order_by
+
 -- Test aliasing of joins

 create view view_of_joins as