Change processing of extended-Query mode so that an unnamed statement

that has parameters is always planned afresh for each Bind command,
treating the parameter values as constants in the planner.  This removes
the performance penalty formerly often paid for using out-of-line
parameters --- with this definition, the planner can do constant folding,
LIKE optimization, etc.  After a suggestion by Andrew@supernews.

1 files changed, 32 insertions, 18 deletions

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 6496b981cf2..2e128ece137 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.505 2006/09/03 03:19:44 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.506 2006/09/06 20:40:48 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -1168,7 +1168,7 @@ exec_parse_message(const char *query_string,	/* string to execute */
 	 * statement, we assume the statement isn't going to hang around long, so
 	 * getting rid of temp space quickly is probably not worth the costs of
 	 * copying parse/plan trees.  So in this case, we set up a special context
-	 * for the unnamed statement, and do all the parsing/planning therein.
+	 * for the unnamed statement, and do all the parsing work therein.
 	 */
 	is_named = (stmt_name[0] != '\0');
 	if (is_named)
@@ -1367,6 +1367,7 @@ exec_bind_message(StringInfo input_message)
 	PreparedStatement *pstmt;
 	Portal		portal;
 	ParamListInfo params;
+	List	   *plan_list;
 	StringInfoData bind_values_str;
 
 	pgstat_report_activity("<BIND>");
@@ -1474,6 +1475,7 @@ exec_bind_message(StringInfo input_message)
 		{
 			Oid			ptype = lfirst_oid(l);
 			int32		plength;
+			Datum		pval;
 			bool		isNull;
 			StringInfoData pbuf;
 			char		csave;
@@ -1532,11 +1534,7 @@ exec_bind_message(StringInfo input_message)
 				else
 					pstring = pg_client_to_server(pbuf.data, plength);
 
-				params->params[paramno].value =
-					OidInputFunctionCall(typinput,
-										 pstring,
-										 typioparam,
-										 -1);
+				pval = OidInputFunctionCall(typinput, pstring, typioparam, -1);
 
 				/* Save the parameter values */
 				appendStringInfo(&bind_values_str, "%s$%d = ",
@@ -1576,10 +1574,7 @@ exec_bind_message(StringInfo input_message)
 				else
 					bufptr = &pbuf;
 
-				params->params[paramno].value = OidReceiveFunctionCall(typreceive,
-																 bufptr,
-																 typioparam,
-																 -1);
+				pval = OidReceiveFunctionCall(typreceive, bufptr, typioparam, -1);
 
 				/* Trouble if it didn't eat the whole buffer */
 				if (!isNull && pbuf.cursor != pbuf.len)
@@ -1596,13 +1591,22 @@ exec_bind_message(StringInfo input_message)
 						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 						 errmsg("unsupported format code: %d",
 								pformat)));
+				pval = 0;		/* keep compiler quiet */
 			}
 
 			/* Restore message buffer contents */
 			if (!isNull)
 				pbuf.data[plength] = csave;
 
+			params->params[paramno].value = pval;
 			params->params[paramno].isnull = isNull;
+			/*
+			 * We mark the params as CONST.  This has no effect if we already
+			 * did planning, but if we didn't, it licenses the planner to
+			 * substitute the parameters directly into the one-shot plan we
+			 * will generate below.
+			 */
+			params->params[paramno].pflags = PARAM_FLAG_CONST;
 			params->params[paramno].ptype = ptype;
 
 			paramno++;
@@ -1641,19 +1645,29 @@ exec_bind_message(StringInfo input_message)
 
 	/*
 	 * If we didn't plan the query before, do it now.  This allows the planner
-	 * to make use of the concrete parameter values we now have.
+	 * to make use of the concrete parameter values we now have.  Because we
+	 * use PARAM_FLAG_CONST, the plan is good only for this set of param
+	 * values, and so we generate the plan in the portal's own memory context
+	 * where it will be thrown away after use.  As in exec_parse_message,
+	 * we make no attempt to recover planner temporary memory until the end
+	 * of the operation.
 	 *
-	 * This happens only for unnamed statements, and so switching into the
-	 * statement context for planning is correct (see notes in
-	 * exec_parse_message).
+	 * XXX because the planner has a bad habit of scribbling on its input,
+	 * we have to make a copy of the parse trees, just in case someone binds
+	 * and executes an unnamed statement multiple times.  FIXME someday
 	 */
 	if (pstmt->plan_list == NIL && pstmt->query_list != NIL)
 	{
-		MemoryContext oldContext = MemoryContextSwitchTo(pstmt->context);
+		MemoryContext oldContext;
 
-		pstmt->plan_list = pg_plan_queries(pstmt->query_list, params, true);
+		oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
+		plan_list = pg_plan_queries(copyObject(pstmt->query_list),
+									params,
+									true);
 		MemoryContextSwitchTo(oldContext);
 	}
+	else
+		plan_list = pstmt->plan_list;
 
 	/*
 	 * Define portal and start execution.
@@ -1664,7 +1678,7 @@ exec_bind_message(StringInfo input_message)
 					  bind_values_str.len ? pstrdup(bind_values_str.data) : NULL,
 					  pstmt->commandTag,
 					  pstmt->query_list,
-					  pstmt->plan_list,
+					  plan_list,
 					  pstmt->context);
 
 	PortalStart(portal, params, InvalidSnapshot);