Re: Statement timeout

> Oops. Previous example was not appropriate. Here are revised
> examples. (in any case, the time consumed at parse and bind are small,
> and I omit the CHECK_FOR_INTERRUPTS after these commands)
>
> [example 1]
>
> statement_timeout = 3s
>
> parse(statement1) -- time 0. set statement timout timer
> bind(statement1, portal1)
> execute(portal1) -- took 2 seconds
> CHECK_FOR_INTERRUPTS -- 2 seconds passed since time 0. statement timeout does not fire
> parse(statement2)
> bind(statement2, portal2)
> execute(portal2) -- took 2 seconds
> CHECK_FOR_INTERRUPTS -- 4 seconds passed since time 0. the statement timeout fires!
>
> Another example.
>
> [example 2]
>
> statement_timeout = 3s
>
> parse(statement1) -- time 0. set statement timout timer
> bind(statement1, portal1)
> execute(portal1) -- took 1 second
> CHECK_FOR_INTERRUPTS -- 1 second passed since time 0. statement timeout does not fire
> parse(statement2)
> bind(statement2, portal2)
> execute(portal2) -- took 1 second
> CHECK_FOR_INTERRUPTS -- 2 seconds passed since time 0. the statement timeout fires!
> [client is idle for 2 seconds]
> sync
> CHECK_FOR_INTERRUPTS -- 4 seconds passed since time 0. the statement timeout fires!
>
> I think current code is good in detecting statement timeout if each
> command execution time actually exceeds the specified timeout. However
> it could report false statement timeout in some cases like above.

Here is the patch against master branch to deal with the problem. I
create new functions in tcop/postgres.c:

static void enable_statement_timeout(void);
static void disable_statement_timeout(void);

Before the code was in start_xact_command() and finish_xact_command()
but I want to manage to disable timeout in exec_execute_command, so I
separated the code into the new functions.

Also start_xact_command() and finish_xact_command() were modified to
use these new functions to avoid code duplication.

I tested the patch using small C program linked with modified libpq
(PQsendQueryParams was modified to issue "flush" message instead of
"sync" message). The statement timeout was set to 3 seconds. With
these test programs, client sends pg_sleep(2) and flush message then
sleep 10 seconds. With current PostgreSQL, this triggers statement
timeout while the client is sleeping. With patched PostgreSQL, this
does not trigger the timeout as expected.

All regression tests passed.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp