Fix for log_executor_stats

The log_executor_stats config variable doesn't work 100%.  It shows
stats for only certain SQL queries.  Looking at utils/portal.h:

 * We have several execution strategies for Portals, depending on what
 * query or queries are to be executed.  (Note: in all cases, a Portal
 * executes just a single source-SQL query, and thus produces just a
 * single result from the user's viewpoint.  However, the rule rewriter
 * may expand the single source query to zero or many actual queries.)
 *
 * PORTAL_ONE_SELECT: the portal contains one single SELECT query.  We run
 * the Executor incrementally as results are demanded.  This strategy also
 * supports holdable cursors (the Executor results can be dumped into a
 * tuplestore for access after transaction completion).
 *
 * PORTAL_UTIL_SELECT: the portal contains a utility statement that returns
 * a SELECT-like result (for example, EXPLAIN or SHOW).  On first execution,
 * we run the statement and dump its results into the portal tuplestore;
 * the results are then returned to the client as demanded.
 *
 * PORTAL_MULTI_QUERY: all other cases.  Here, we do not support partial
 * execution: the portal's queries will be run to completion on first call.

it only logs executor stats for PORTAL_MULTI_QUERY queries.  I assume
this was done so that individual queries are logged rather than the
entire multi-query.  However, the code shows no executor stats for
non-multi queries, which is certainly a bug.  Even a simple "SELECT col
FROM tab" or "SELECT 1" emits no statistics.

This used to work in the past, but it appears broken in 7.4.X too.  I
guess I should fix it there too, though obviously very few people use
this feature or we would have gotten reports.

The attached fix keeps the multi-query stats code unchanged, but adds
stats for non-multi-query cases.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
Index: src/backend/tcop/pquery.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/tcop/pquery.c,v
retrieving revision 1.74
diff -c -c -r1.74 pquery.c
*** src/backend/tcop/pquery.c    29 Nov 2003 19:51:57 -0000    1.74
--- src/backend/tcop/pquery.c    4 Mar 2004 18:29:03 -0000
***************
*** 406,411 ****
--- 406,415 ----
      if (completionTag)
          completionTag[0] = '\0';

+     /* PORTAL_MULTI_QUERY logs its own stats per query */
+     if (log_executor_stats && portal->strategy != PORTAL_MULTI_QUERY)
+         ResetUsage();
+
      /*
       * Check for improper portal use, and mark portal active.
       */
***************
*** 499,504 ****
--- 503,511 ----

      PortalContext = savePortalContext;
      QueryContext = saveQueryContext;
+
+     if (log_executor_stats && portal->strategy != PORTAL_MULTI_QUERY)
+         ShowUsage("EXECUTOR STATISTICS");

      return result;
  }