From 43baec8366b1d049e1088c0bdc1b7d39cdb7e858 Mon Sep 17 00:00:00 2001
From: "Stephen R. van den Berg" <srb@cuci.nl>
Date: Wed, 4 Mar 2020 15:40:09 +0100
Subject: [PATCH] pgsql: Toggle cache_autoprepared_statements default.
---
CHANGES | 4 ++++
lib/modules/Sql.pmod/pgsql.pike | 12 ++++++++----
2 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/CHANGES b/CHANGES
index f2033f1972..f9c4b4ed28 100644
--- a/CHANGES
+++ b/CHANGES
@@ -192,6 +192,10 @@ o Sql.pgsql
- Simplify error handling.
+ - Toggle cache_autoprepared_statements default to off;
+ turning it on triggers a bug in PostgreSQL sometimes
+ that causes spikes in CPU usage of the database.
+
o SSL
- When verifying the hostname against the certificate, only accept *
diff --git a/lib/modules/Sql.pmod/pgsql.pike b/lib/modules/Sql.pmod/pgsql.pike
index 35b3334dd4..9c09529772 100644
--- a/lib/modules/Sql.pmod/pgsql.pike
+++ b/lib/modules/Sql.pmod/pgsql.pike
@@ -143,10 +143,12 @@ protected string _sprintf(int type) {
//! statement),
//! but it can speed up parsing due to increased parallelism.
//! @member int "cache_autoprepared_statements"
-//! If set to zero, it disables the automatic statement prepare and
+//! If set to one, it enables the automatic statement prepare and
//! cache logic; caching prepared statements can be problematic
//! when stored procedures and tables are redefined which leave stale
//! references in the already cached prepared statements.
+//! The default is off, because PostgreSQL 10.1 (at least)
+//! has a bug that makes it spike to 100% CPU sometimes when this is on.
//! @member string "client_encoding"
//! Character encoding for the client side, it defaults to using
//! the default encoding specified by the database, e.g.
@@ -929,7 +931,10 @@ private void startquery(int forcetext, .pgsql_util.sql_result portal, string q,
if (!sizeof(preparedname) || !tp || !tp.preparedname) {
if (!sizeof(preparedname))
preparedname =
- (portal._unnamedstatementkey = proxy.unnamedstatement->trylock(1))
+ (portal._unnamedstatementkey =
+ (proxy.options.cache_autoprepared_statements
+ ? proxy.unnamedstatement->trylock
+ : proxy.unnamedstatement->lock)(1))
? "" : PTSTMTPREFIX + int2hex(ptstmtcount++);
PD("Parse statement %O=%O\n", preparedname, q);
plugbuffer = c->start();
@@ -1145,8 +1150,7 @@ private void startquery(int forcetext, .pgsql_util.sql_result portal, string q,
#endif
preparedname = tp.preparedname;
} else if(tp.trun && tp.tparse*FACTORPLAN >= tp.trun
- && (undefinedp(options.cache_autoprepared_statements)
- || options.cache_autoprepared_statements))
+ && options.cache_autoprepared_statements)
preparedname = PREPSTMTPREFIX + int2hex(pstmtcount++);
} else {
if (proxy.totalhits >= cachedepth)
--
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