Re: Statement timeout in pg_rewind

[Alexander Kukushkin]

On Tue, 27 Aug 2019 at 08:36, Michael Paquier <mich...@paquier.xyz> wrote:

> I'd rather be on the safe side and as we are looking at this at this
> area..  Who knows if this logic is going to change in the future and
> how it will change.

Agree.

> Oops, I misread this part.  What about a simple wrapper
> run_simple_command which checks after PGRES_COMMAND_OK, and frees the
> result then?  This could be used for the temporary table creation and
> when setting synchronous_commit.

Done, please see the next version attached.

Regards,
--
Alexander Kukushkin

diff --git a/src/bin/pg_rewind/libpq_fetch.c b/src/bin/pg_rewind/libpq_fetch.c
index 37eccc3126..e2dbc9fdf6 100644
--- a/src/bin/pg_rewind/libpq_fetch.c
+++ b/src/bin/pg_rewind/libpq_fetch.c
@@ -39,6 +39,7 @@ static PGconn *conn = NULL;
 static void receiveFileChunks(const char *sql);
 static void execute_pagemap(datapagemap_t *pagemap, const char *path);
 static char *run_simple_query(const char *sql);
+static void run_simple_command(const char *sql);
 
 void
 libpqConnect(const char *connstr)
@@ -54,6 +55,11 @@ libpqConnect(const char *connstr)
 	if (showprogress)
 		pg_log_info("connected to server");
 
+	/* We don't want our queries canceled */
+	run_simple_command("SET statement_timeout = 0");
+	run_simple_command("SET lock_timeout = 0");
+	run_simple_command("SET idle_in_transaction_session_timeout = 0");
+
 	res = PQexec(conn, ALWAYS_SECURE_SEARCH_PATH_SQL);
 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
 		pg_fatal("could not clear search_path: %s",
@@ -88,11 +94,7 @@ libpqConnect(const char *connstr)
 	 * replication, and replication isn't working for some reason, we don't
 	 * want to get stuck, waiting for it to start working again.
 	 */
-	res = PQexec(conn, "SET synchronous_commit = off");
-	if (PQresultStatus(res) != PGRES_COMMAND_OK)
-		pg_fatal("could not set up connection context: %s",
-				 PQresultErrorMessage(res));
-	PQclear(res);
+	run_simple_command("SET synchronous_commit = off");
 }
 
 /*
@@ -122,6 +124,25 @@ run_simple_query(const char *sql)
 	return result;
 }
 
+/*
+ * Runs a command.
+ * In case of failure pg_fatal exits with code=1.
+ */
+static void
+run_simple_command(const char *sql)
+{
+	PGresult   *res;
+	char	   *result;
+
+	res = PQexec(conn, sql);
+
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("error running command (%s) in source server: %s",
+				 sql, PQresultErrorMessage(res));
+
+	PQclear(res);
+}
+
 /*
  * Calls pg_current_wal_insert_lsn() function
  */
@@ -427,12 +448,7 @@ libpq_executeFileMap(filemap_t *map)
 	 * need to fetch.
 	 */
 	sql = "CREATE TEMPORARY TABLE fetchchunks(path text, begin int8, len int4);";
-	res = PQexec(conn, sql);
-
-	if (PQresultStatus(res) != PGRES_COMMAND_OK)
-		pg_fatal("could not create temporary table: %s",
-				 PQresultErrorMessage(res));
-	PQclear(res);
+	run_simple_command(sql);
 
 	sql = "COPY fetchchunks FROM STDIN";
 	res = PQexec(conn, sql);