Re: Using timestamp(tz) in C functions

On Fri, Jul 29, 2016 at 11:49 AM, Vitaly Burovoy <vitaly(dot)burovoy(at)gmail(dot)com>
wrote:

> On 7/29/16, Keith Fiske <keith(at)omniti(dot)com> wrote:
> > On Fri, Jul 29, 2016 at 12:53 AM, Vitaly Burovoy <
> vitaly(dot)burovoy(at)gmail(dot)com>
> > wrote:
> >
> >> On 7/28/16, Keith Fiske <keith(at)omniti(dot)com> wrote:
> >> > Working on trying to get a C version of the maintenance function for
> my
> >> > pg_partman extension working so I can hopefully make it more flexible
> >> > and
> >> > efficient.
> >> >
> >>
> https://gist.github.com/keithf4/81c32bf8b689c74b20c10ad8c91d45a3#file-pg_partman_bgw-c-L532
> >> >
> >> > There's what I've got working so far and links directly to the area
> >> > where
> >> > I'm having a problem. I found the DatumGetTimeTzADTP() function and
> the
> >> > TimeTzADT data type looking through the source and that seems to be
> exactly
> >> > what I'm looking for. However, when I get to the point of trying to
> simply
> >> > use the time value in that variable (line 544), Postgres segfaults.
> So far
> >> > I've just been trying to print the value out to the log to ensure I'm
> >> > pulling it out correctly. The "time" value of the struct appears to be
> >> > an
> >> > int64, so I thought %ld would be the correct, but even using %d or %s
> >> > fails.
> >> >
> >> > Thanks!
> >> >
> >> > --
> >> > Keith Fiske
> >> > Database Administrator
> >> > OmniTI Computer Consulting, Inc.
> >> > http://www.keithf4.com
> >> >
> >>
> >> I think it is not about timestamp(tz), but about usage of SPI.
> >> Since DatumGetTimeTzADTP is just a macros implements type conversion
> >> (declared at src/include/utils/date.h:60 (or 75)) you get segfault not
> >> in it but when the code tries to get value by dereference pointer
> >> (last_partition_timestamp->time).
> >>
> >> Please, answer questions:
> >> 1. How many rows SPI_execute returns (value of "ret" variable)?
> >> 2. Is last_partition_timestamp != NULL? Where it points to?
> >> 3. Try to check SPI_result just after SPI_getbinval. Has it error code?
> >
> >
> > It returns a single row. Here's an example of the results of the two
> > queries that are run that lead to providing the timestamp value
> >
> > keith=# select partition_tablename from
> > partman.show_partitions('partman_test.time_taptest_table', 'DESC') limit
> > 1; partition_tablename
> > --------------------------------
> > time_taptest_table_p2016_08_02
> > (1 row)
> >
> > keith=# select child_start_time from
> >
> partman.show_partition_info('partman_test.time_taptest_table_p2016_08_02',
> > '1 day', 'partman_test.time_taptest_table');
> > child_start_time
> > ------------------------
> > 2016-08-02 00:00:00-04
> > (1 row)
> >
> > So there is valid data. As you're pointing out, this may just be a
> > misunderstanding of how to actually use the Datum retrieval function and
> C
> > in general. Appreciate the assistance.
> >
> > Keith
> >
>
> Please, add next lines (or debug this values via gdb) and post a result:
>
> ret = SPI_execute(buf.data, true, 1);
>
> ereport(NOTICE, (errmsg("query=%s", buf.data)));
> ereport(NOTICE, (errmsg("ret=%i -- rows=%ju", ret, SPI_processed)));
>
> last_partition_timestamp =
> DatumGetTimeTzADTP(SPI_getbinval(SPI_tuptable->vals[0],
> SPI_tuptable->tupdesc, 1, &isnull));
>
> ereport(NOTICE, (errmsg("SPI_result=%d -- ptr=%p", SPI_result,
> (void*)last_partition_timestamp )));
>
> /* elog(LOG, "Just seeing if it's time partitioned: %ld",
> last_partition_timestamp->time); --prevent segfaulting */
>
>
> --
> Best regards,
> Vitaly Burovoy
>

From the postgresql logs:

2016-07-29 11:59:39 EDT [] [2021]: [10-1] user=,db=,e=00000 LOG: Just
checking that this thing is working. Loop: 0, parent_table:
partman_test.time_taptest_table, partition_type: time, partition_interval:
00:15:00, control: col3, premake: 4, datetime_string: %YYYY_MM_DD_HH24MI,
undo_in_progress: 0, sub_partition_set_full: 0, epoch: 0,
infinite_time_partitions: 0
2016-07-29 11:59:39 EDT [] [2021]: [11-1] user=,db=,e=00000 NOTICE:
query=SELECT child_start_time FROM
partman.show_partition_info('partman_test.time_taptest_table_p2016_07_29_1245',
'00:15:00', 'partman_test.time_taptest_table')
2016-07-29 11:59:39 EDT [] [2021]: [12-1] user=,db=,e=00000 NOTICE: ret=5
-- rows=1
2016-07-29 11:59:39 EDT [] [2021]: [13-1] user=,db=,e=00000 NOTICE:
SPI_result=0 -- ptr=0x1dbc7bd713b00
2016-07-29 11:59:41 EDT [] [2012]: [10-1] user=,db=,e=00000 LOG: worker
process: pg_partman dynamic background worker (dbname=keith) (PID 2021) was
terminated by signal 11: Segmentation fault

FYI, Also got these notices when compiling:

gcc -Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute
-Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard
-g -O2 -fpic -I. -I./ -I/opt/pgsql953/include/server
-I/opt/pgsql953/include/internal -D_GNU_SOURCE -c -o src/pg_partman_bgw.o
src/pg_partman_bgw.c -MMD -MP -MF .deps/pg_partman_bgw.Po
In file included from /opt/pgsql953/include/server/postgres.h:48:0,
from src/pg_partman_bgw.c:10:
src/pg_partman_bgw.c: In function ‘pg_partman_run_maintenance_c’:
src/pg_partman_bgw.c:623:41: warning: format ‘%ju’ expects argument of type
‘uintmax_t’, but argument 3 has type ‘uint32 {aka unsigned int}’ [-Wformat=]
ereport(NOTICE, (errmsg("ret=%i -- rows=%ju", ret,
SPI_processed)));
^
/opt/pgsql953/include/server/utils/elog.h:117:14: note: in definition of
macro ‘ereport_domain’
errfinish rest; \
^
src/pg_partman_bgw.c:623:17: note: in expansion of macro ‘ereport’
ereport(NOTICE, (errmsg("ret=%i -- rows=%ju", ret,
SPI_processed)));
^