From 2b2bacdca0100f50ba4f79cda53514b6e5114e8f Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 25 Oct 2019 11:15:50 -0400 Subject: [PATCH] Reset statement_timeout between queries of a multi-query string. Historically, we started the timer (if StatementTimeout > 0) at the beginning of a simple-Query message and usually let it run until the end, so that the timeout limit applied to the entire query string, and intra-string changes of the statement_timeout GUC had no effect. But, confusingly, a COMMIT within the string would reset the state and allow a fresh timeout cycle to start with the current setting. Commit f8e5f156b changed the behavior of statement_timeout for extended query protocol, and as an apparently-unintended side effect, a change in the statement_timeout GUC during a multi-statement simple-Query message might have an effect immediately --- but only if it was going from "disabled" to "enabled". This is all pretty confusing, not to mention completely undocumented. Let's change things so that the timeout is always reset between queries of a multi-query string, whether they're transaction control commands or not. Thus the active timeout setting is applied to each query in the string, separately. This costs a few more cycles if statement_timeout is active, but it provides much more intuitive behavior, especially if one changes statement_timeout in one of the queries of the string. Also, add something to the documentation to explain all this. Per bug #16035 from Raj Mohite. Although this is a bug fix, I'm hesitant to back-patch it; conceivably somebody has worked out the old behavior and is depending on it. (But note that this change should make the behavior less restrictive in most cases, since the timeout will now be applied to shorter segments of code.) Discussion: https://postgr.es/m/16035-456e6e69ebfd4374@postgresql.org --- doc/src/sgml/config.sgml | 23 ++++++++++++++++++----- src/backend/tcop/postgres.c | 12 +++++++++++- 2 files changed, 29 insertions(+), 6 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 886632ff43..c1da75fbab 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -7592,11 +7592,24 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; - Abort any statement that takes more than the specified duration - (defaults to milliseconds), starting from the time the command arrives at the server - from the client. If log_min_error_statement is set to - ERROR or lower, the statement that timed out will also be - logged. A value of zero (the default) turns this off. + Abort any statement that takes more than the specified duration. + If log_min_error_statement is set + to ERROR or lower, the statement that timed out + will also be logged. + If the value is specified without units, it is taken as milliseconds. + A value of zero (the default) disables the timeout. + + + + The timeout is measured from the time a command arrives at the + server until it is completed by the server. If multiple SQL + statements appear in a single simple-Query message, the timeout + is applied to each statement separately. + (PostgreSQL versions before 13 usually + treated the timeout as applying to the whole query string.) + In extended query protocol, the timeout starts running when any + query-related message (Parse, Bind, Execute, Describe) arrives, and + it is cancelled by completion of an Execute or Sync message. diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c index e8d8e6f828..1ecaba0d57 100644 --- a/src/backend/tcop/postgres.c +++ b/src/backend/tcop/postgres.c @@ -1270,6 +1270,13 @@ exec_simple_query(const char *query_string) * those that start or end a transaction block. */ CommandCounterIncrement(); + + /* + * Disable statement timeout between queries of a multi-query + * string, so that the timeout applies separately to each query. + * (Our next loop iteration will start a fresh timeout.) + */ + disable_statement_timeout(); } /* @@ -2135,7 +2142,10 @@ exec_execute_message(const char *portal_name, long max_rows) */ CommandCounterIncrement(); - /* full command has been executed, reset timeout */ + /* + * Disable statement timeout whenever we complete an Execute + * message. The next protocol message will start a fresh timeout. + */ disable_statement_timeout(); }