checking for interrupts during heap insertion
Hi,
While talking to Amit Kapila this morning, he mentioned to me that
there seem to be no CHECK_FOR_INTERRUPTS() calls anywhere in
heap_multi_insert() or the functions it calls. Should there be?
By way of contrast, heapgetpage() has this:
/*
* Be sure to check for interrupts at least once per page. Checks at
* higher code levels won't be able to stop a seqscan that encounters many
* pages' worth of consecutive dead tuples.
*/
CHECK_FOR_INTERRUPTS();
In heap_multi_insert(), we first do heap_prepare_insert() on each
tuple, which may involve dirtying many pages, since it handles TOAST.
Then, we loop over the tuples themselves and dirty a bunch more pages.
All of that will normally happen pretty quickly, but if the I/O
subsystem is very slow for some reason, such as due to heavy system
load, then it might take quite a long time. I'm thinking we might
want a CHECK_FOR_INTERRUPTS() in the following two places:
1. Inside toast_save_datum, at the top of the loop that starts with
"while (data_todo > 0)".
2. Inside heap_multi_insert, at the top of the loop that starts with
"while (ndone < ntuples)".
Thoughts?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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On 06/23/2014 08:07 PM, Robert Haas wrote:
While talking to Amit Kapila this morning, he mentioned to me that
there seem to be no CHECK_FOR_INTERRUPTS() calls anywhere in
heap_multi_insert() or the functions it calls. Should there be?
Haven't heard any complaints, but I guess..
By way of contrast, heapgetpage() has this:
/*
* Be sure to check for interrupts at least once per page. Checks at
* higher code levels won't be able to stop a seqscan that encounters many
* pages' worth of consecutive dead tuples.
*/
CHECK_FOR_INTERRUPTS();In heap_multi_insert(), we first do heap_prepare_insert() on each
tuple, which may involve dirtying many pages, since it handles TOAST.
Then, we loop over the tuples themselves and dirty a bunch more pages.
All of that will normally happen pretty quickly, but if the I/O
subsystem is very slow for some reason, such as due to heavy system
load, then it might take quite a long time. I'm thinking we might
want a CHECK_FOR_INTERRUPTS() in the following two places:1. Inside toast_save_datum, at the top of the loop that starts with
"while (data_todo > 0)".
2. Inside heap_multi_insert, at the top of the loop that starts with
"while (ndone < ntuples)".
Seems reasonable.
- Heikki
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On Mon, Jun 23, 2014 at 3:30 PM, Heikki Linnakangas
<hlinnakangas@vmware.com> wrote:
load, then it might take quite a long time. I'm thinking we might
want a CHECK_FOR_INTERRUPTS() in the following two places:1. Inside toast_save_datum, at the top of the loop that starts with
"while (data_todo > 0)".
2. Inside heap_multi_insert, at the top of the loop that starts with
"while (ndone < ntuples)".Seems reasonable.
OK, done.
I don't have time to pursue this at the moment, but while looking at
this, I was also wondering if toast_save_datum() ought to be rewritten
to use heap_multi_insert(). I seem to recall that you found that the
multi-insert optimization mostly benefited narrow tables, so I'm not
sure whether it would work out to a win, but maybe it'd be worth
investigating.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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