Fix failure to ensure that a snapshot is available to datatype input functions

when they are invoked by the parser.  We had been setting up a snapshot at
plan time but really it needs to be done earlier, before parse analysis.
Per report from Dmitry Koterov.

Also fix two related problems discovered while poking at this one:
exec_bind_message called datatype input functions without establishing a
snapshot, and SET CONSTRAINTS IMMEDIATE could call trigger functions without
establishing a snapshot.

Backpatch to 8.2.  The underlying problem goes much further back, but it is
masked in 8.1 and before because we didn't attempt to invoke domain check
constraints within datatype input.  It would only be exposed if a C-language
datatype input function used the snapshot; which evidently none do, or we'd
have heard complaints sooner.  Since this code has changed a lot over time,
a back-patch is hardly risk-free, and so I'm disinclined to patch further
than absolutely necessary.

1 files changed, 52 insertions, 5 deletions

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index b09401652b8..97b9b170b92 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 1.560 2008/12/09 15:59:39 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.561 2008/12/13 02:00:19 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -685,6 +685,9 @@ pg_plan_query(Query *querytree, int cursorOptions, ParamListInfo boundParams)
 	if (querytree->commandType == CMD_UTILITY)
 		return NULL;
 
+	/* Planner must have a snapshot in case it calls user-defined functions. */
+	Assert(ActiveSnapshotSet());
+
 	TRACE_POSTGRESQL_QUERY_PLAN_START();
 
 	if (log_planner_stats)
@@ -872,6 +875,7 @@ exec_simple_query(const char *query_string)
 	foreach(parsetree_item, parsetree_list)
 	{
 		Node	   *parsetree = (Node *) lfirst(parsetree_item);
+		bool		snapshot_set = false;
 		const char *commandTag;
 		char		completionTag[COMPLETION_TAG_BUFSIZE];
 		List	   *querytree_list,
@@ -914,6 +918,15 @@ exec_simple_query(const char *query_string)
 		CHECK_FOR_INTERRUPTS();
 
 		/*
+		 * Set up a snapshot if parse analysis/planning will need one.
+		 */
+		if (analyze_requires_snapshot(parsetree))
+		{
+			PushActiveSnapshot(GetTransactionSnapshot());
+			snapshot_set = true;
+		}
+
+		/*
 		 * OK to analyze, rewrite, and plan this query.
 		 *
 		 * Switch to appropriate context for constructing querytrees (again,
@@ -924,7 +937,11 @@ exec_simple_query(const char *query_string)
 		querytree_list = pg_analyze_and_rewrite(parsetree, query_string,
 												NULL, 0);
 
-		plantree_list = pg_plan_queries(querytree_list, 0, NULL, true);
+		plantree_list = pg_plan_queries(querytree_list, 0, NULL, false);
+
+		/* Done with the snapshot used for parsing/planning */
+		if (snapshot_set)
+			PopActiveSnapshot();
 
 		/* If we got a cancel signal in analysis or planning, quit */
 		CHECK_FOR_INTERRUPTS();
@@ -939,7 +956,7 @@ exec_simple_query(const char *query_string)
 
 		/*
 		 * We don't have to copy anything into the portal, because everything
-		 * we are passsing here is in MessageContext, which will outlive the
+		 * we are passing here is in MessageContext, which will outlive the
 		 * portal anyway.
 		 */
 		PortalDefineQuery(portal,
@@ -1178,6 +1195,7 @@ exec_parse_message(const char *query_string,	/* string to execute */
 	if (parsetree_list != NIL)
 	{
 		Query	   *query;
+		bool		snapshot_set = false;
 		int			i;
 
 		raw_parse_tree = (Node *) linitial(parsetree_list);
@@ -1203,6 +1221,15 @@ exec_parse_message(const char *query_string,	/* string to execute */
 						"commands ignored until end of transaction block")));
 
 		/*
+		 * Set up a snapshot if parse analysis/planning will need one.
+		 */
+		if (analyze_requires_snapshot(raw_parse_tree))
+		{
+			PushActiveSnapshot(GetTransactionSnapshot());
+			snapshot_set = true;
+		}
+
+		/*
 		 * OK to analyze, rewrite, and plan this query.  Note that the
 		 * originally specified parameter set is not required to be complete,
 		 * so we have to use parse_analyze_varparams().
@@ -1249,9 +1276,13 @@ exec_parse_message(const char *query_string,	/* string to execute */
 		}
 		else
 		{
-			stmt_list = pg_plan_queries(querytree_list, 0, NULL, true);
+			stmt_list = pg_plan_queries(querytree_list, 0, NULL, false);
 			fully_planned = true;
 		}
+
+		/* Done with the snapshot used for parsing/planning */
+		if (snapshot_set)
+			PopActiveSnapshot();
 	}
 	else
 	{
@@ -1375,6 +1406,7 @@ exec_bind_message(StringInfo input_message)
 	List	   *plan_list;
 	MemoryContext oldContext;
 	bool		save_log_statement_stats = log_statement_stats;
+	bool		snapshot_set = false;
 	char		msec_str[32];
 
 	/* Get the fixed part of the message */
@@ -1495,6 +1527,17 @@ exec_bind_message(StringInfo input_message)
 		saved_stmt_name = NULL;
 
 	/*
+	 * Set a snapshot if we have parameters to fetch (since the input
+	 * functions might need it) or the query isn't a utility command (and
+	 * hence could require redoing parse analysis and planning).
+	 */
+	if (numParams > 0 || analyze_requires_snapshot(psrc->raw_parse_tree))
+	{
+		PushActiveSnapshot(GetTransactionSnapshot());
+		snapshot_set = true;
+	}
+
+	/*
 	 * Fetch parameters, if any, and store in the portal's memory context.
 	 */
 	if (numParams > 0)
@@ -1682,7 +1725,7 @@ exec_bind_message(StringInfo input_message)
 		 */
 		oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
 		query_list = copyObject(cplan->stmt_list);
-		plan_list = pg_plan_queries(query_list, 0, params, true);
+		plan_list = pg_plan_queries(query_list, 0, params, false);
 		MemoryContextSwitchTo(oldContext);
 
 		/* We no longer need the cached plan refcount ... */
@@ -1691,6 +1734,10 @@ exec_bind_message(StringInfo input_message)
 		cplan = NULL;
 	}
 
+	/* Done with the snapshot used for parameter I/O and parsing/planning */
+	if (snapshot_set)
+		PopActiveSnapshot();
+
 	/*
 	 * Define portal and start execution.
 	 */