Tweak make_inh_translation_lists() to check the common case wherein parent and

child attnums are the same, before it grovels through each and every child
column looking for a name match.  Saves some time in large inheritance trees,
per example from Greg.

diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 5b4b312df1108789191c0a656676806fd7d11d78..2b273f738a8bf31152cbdf9467886a33428808e4 100644 (file)
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.140 2007/03/17 00:11:04 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.141 2007/04/21 05:56:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -973,31 +973,42 @@ make_inh_translation_lists(Relation oldrelation, Relation newrelation,
         * Otherwise we have to search for the matching column by name.
         * There's no guarantee it'll have the same column position, because
         * of cases like ALTER TABLE ADD COLUMN and multiple inheritance.
+        * However, in simple cases it will be the same column number, so
+        * try that before we go groveling through all the columns.
+        *
+        * Note: the test for (att = ...) != NULL cannot fail, it's just a
+        * notational device to include the assignment into the if-clause.
         */
-       for (new_attno = 0; new_attno < newnatts; new_attno++)
+       if (old_attno < newnatts &&
+           (att = new_tupdesc->attrs[old_attno]) != NULL &&
+           !att->attisdropped && att->attinhcount != 0 &&
+           strcmp(attname, NameStr(att->attname)) == 0)
+           new_attno = old_attno;
+       else
        {
-           att = new_tupdesc->attrs[new_attno];
-           if (att->attisdropped || att->attinhcount == 0)
-               continue;
-           if (strcmp(attname, NameStr(att->attname)) != 0)
-               continue;
-           /* Found it, check type */
-           if (atttypid != att->atttypid || atttypmod != att->atttypmod)
-               elog(ERROR, "attribute \"%s\" of relation \"%s\" does not match parent's type",
+           for (new_attno = 0; new_attno < newnatts; new_attno++)
+           {
+               att = new_tupdesc->attrs[new_attno];
+               if (!att->attisdropped && att->attinhcount != 0 &&
+                   strcmp(attname, NameStr(att->attname)) == 0)
+                   break;
+           }
+           if (new_attno >= newnatts)
+               elog(ERROR, "could not find inherited attribute \"%s\" of relation \"%s\"",
                     attname, RelationGetRelationName(newrelation));
-
-           numbers = lappend_int(numbers, new_attno + 1);
-           vars = lappend(vars, makeVar(newvarno,
-                                        (AttrNumber) (new_attno + 1),
-                                        atttypid,
-                                        atttypmod,
-                                        0));
-           break;
        }
 
-       if (new_attno >= newnatts)
-           elog(ERROR, "could not find inherited attribute \"%s\" of relation \"%s\"",
+       /* Found it, check type */
+       if (atttypid != att->atttypid || atttypmod != att->atttypmod)
+           elog(ERROR, "attribute \"%s\" of relation \"%s\" does not match parent's type",
                 attname, RelationGetRelationName(newrelation));
+
+       numbers = lappend_int(numbers, new_attno + 1);
+       vars = lappend(vars, makeVar(newvarno,
+                                    (AttrNumber) (new_attno + 1),
+                                    atttypid,
+                                    atttypmod,
+                                    0));
    }
 
    *col_mappings = numbers;