From: Pavan Deolasee <pavan.deolasee@gmail.com>
Date: Fri, 20 Jan 2017 09:45:43 +0000 (+0530)
Subject: A very naive way to deal with the fact that RemoteQuery (which EXECUTE DIRECT
X-Git-Tag: XL_10_R1BETA1~331
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=8854567268857dff727361fa14eb786e4862ebf4;p=postgres-xl.git

A very naive way to deal with the fact that RemoteQuery (which EXECUTE DIRECT
internally uses) cannot support cursor fetch.

FOR EXECUTE query inside plpgsql uses cursor mechanism to fetch a few tuples at
a time. But that fails badly when the query is a EXECUTE DIRECT statement
because we internally use RemoteQuery to execute that. Instead just fetch 10000
tuples at a time and complain if RemoteQuery returns more than 10000 rows. May
be that's enough for the scenario that we're trying to address where a global
view can be created using EXECUTE DIRECT
---

diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 428743532b..31ae38e395 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -5169,6 +5169,7 @@ exec_for_query(PLpgSQL_execstate *estate, PLpgSQL_stmt_forq *stmt,
 	bool		found = false;
 	int			rc = PLPGSQL_RC_OK;
 	uint64		n;
+	long		count;
 
 	/*
 	 * Determine if we assign to a record or a row
@@ -5191,10 +5192,21 @@ exec_for_query(PLpgSQL_execstate *estate, PLpgSQL_stmt_forq *stmt,
 	 * few more rows to avoid multiple trips through executor startup
 	 * overhead.
 	 */
-	SPI_cursor_fetch(portal, true, prefetch_ok ? 10 : 1);
+#define MAX_REMOTE_QUERY_FETCH	10000	
+	if (IsA(linitial(portal->stmts), PlannedStmt) &&
+		IsA(((PlannedStmt *) linitial(portal->stmts))->planTree, RemoteQuery))
+		count = MAX_REMOTE_QUERY_FETCH;
+	else
+		count = prefetch_ok ? 10 : 1;
+
+	SPI_cursor_fetch(portal, true, count);
 	tuptab = SPI_tuptable;
 	n = SPI_processed;
 
+	if (n == MAX_REMOTE_QUERY_FETCH)
+		elog(ERROR, "Can fetch only %d tuples via RemoteQuery execution",
+				MAX_REMOTE_QUERY_FETCH);
+
 	/*
 	 * If the query didn't return any rows, set the target to NULL and fall
 	 * through with found = false.