Re: PQexec does not return.

Hi Martin,

I have got same problem as mentioned by you. As per your comment it
seems this problem is due to memory leak. Could you explain the exact
reason of this problem. How it is related to mem-leak.

Regards & Thanks
-Shalendra

On Jan 15, 3:51 pm, smar(dot)(dot)(dot)(at)nec(dot)co(dot)nz (Steve Martin) wrote:
> Hi All,
>
> Found the problem. This was caused by a memory leak in our application.
>
> Regards
> Steve Martin
>
> Steve Martin wrote:
> > Hi All,
>
> > We have an intermittent problem where PQexec does not seem to return
> > even though the server seems to have sent the results.
>
> > From the gdb output , the sql statement can be seen, and from the log,
> > the result can be seen to be sent. Both process are running on the
> > same machine. Version of postgres and other info:
>
> > 1. Postgres Version 8.1.4
> > 2. Machine HP rx4640
> > 3. OS: HPUX 11.23
> > 4. Mem 8G
>
> > Has anyone seen this type of problem before, can it be cause by a
> > TCP/IP communication failure?
>
> > From gdb:
>
> > % /opt/langtools/bin/gdb /path/name -p 3587
> > HP gdb 5.2 for HP Itanium (32 or 64 bit) and target HP-UX 11.2x.
> > Copyright 1986 - 2001 Free Software Foundation, Inc.
> > Hewlett-Packard Wildebeest 5.2 (based on GDB) is covered by the
> > GNU General Public License. Type "show copying" to see the
> > conditions to
> > change it and/or distribute copies. Type "show warranty" for
> > warranty/support.
> > ..
> > Attaching to program: /path/name, process 3587
>
> > warning: No unwind information found.
> > Skipping this library /usr/lib/hpux32/libcl.so.1.
>
> > 0x60000000c0342810:0 in _poll_sys+0x30 () from
> > /usr/lib/hpux32/libc.so.1
> > (gdb) bt
> > #0 0x60000000c0342810:0 in _poll_sys+0x30 () from
> > /usr/lib/hpux32/libc.so.1
> > #1 0x60000000c03553e0:0 in poll+0x160 () from
> > /usr/lib/hpux32/libc.so.1
> > #2 0x60000000cefa75b0:0 in pqSocketCheck+0xb00 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > #3 0x60000000cefa77c0:0 in pqWaitTimed+0x40 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > #4 0x60000000cefa7890:0 in pqWait+0x40 () from
> > /usr/local/pgsql/lib/libpq.so.4
> > #5 0x60000000cefa53b0:0 in PQgetResult+0x180 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > #6 0x60000000cefa56f0:0 in PQexecFinish+0x40 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > #7 0x60000000c1c83870:0 in DBIFPostgreSelect::getRecord
> > (this=0x40114840)
> > at DBIFPostgre.C:1688
> > #8 0x60000000c1c73d20:0 in DBIFPostgreSelect::selectNext
> > (this=0x40114840,
> > rst=(at)0x7fff5210) at DBIFPostgre.C:1902
> > #9 0x60000000c1c64b90:0 in DBIFSelect::selectNext (this=0x7fff5240,
> > rst=(at)0x7fff5210) at DBIF.C:2704
> > #10 0x404ff00:0 in TableStatus::checkDeferredTR (this=0x403104c0)
> > at DbSContTable.C:1468
> > #11 0x405b430:0 in TableStatusManager::checkDeferredTR
> > (this=0x400bde90)
> > at DbSContTable.C:3146
> > #12 0x4068960:0 in Controller::go (this=0x7fffc320) at
> > DbSController.C:1950
> > #13 0x406b1b0:0 in main (argc=1, argv=0x7fffed74) at DbSContMain.C:137
> > (gdb) q
> > The program is running. Quit anyway (and detach it)? (y or n) y
> > Detaching from program: /path/name, process 3587
>
> > % /opt/langtools/bin/gdb /path/name -p 3587
> > HP gdb 5.2 for HP Itanium (32 or 64 bit) and target HP-UX 11.2x.
> > Copyright 1986 - 2001 Free Software Foundation, Inc.
> > Hewlett-Packard Wildebeest 5.2 (based on GDB) is covered by the
> > GNU General Public License. Type "show copying" to see the
> > conditions to
> > change it and/or distribute copies. Type "show warranty" for
> > warranty/support.
> > ..
> > Attaching to program: /path/name, process 3587
>
> > warning: No unwind information found.
> > Skipping this library /usr/lib/hpux32/libcl.so.1.
>
> > 0x60000000c0342810:0 in _poll_sys+0x30 () from
> > /usr/lib/hpux32/libc.so.1
> > (gdb) up
> > #1 0x60000000c03553e0:0 in poll+0x160 () from
> > /usr/lib/hpux32/libc.so.1
> > (gdb) up
> > #2 0x60000000cefa75b0:0 in pqSocketCheck+0xb00 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > (gdb) up
> > #3 0x60000000cefa77c0:0 in pqWaitTimed+0x40 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > (gdb) up
> > #4 0x60000000cefa7890:0 in pqWait+0x40 () from
> > /usr/local/pgsql/lib/libpq.so.4
> > (gdb) up
> > #5 0x60000000cefa53b0:0 in PQgetResult+0x180 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > (gdb) up
> > #6 0x60000000cefa56f0:0 in PQexecFinish+0x40 ()
> > from /usr/local/pgsql/lib/libpq.so.4
> > (gdb) up
> > #7 0x60000000c1c83870:0 in DBIFPostgreSelect::getRecord
> > (this=0x40114840)
> > at DBIFPostgre.C:1688
> > 1688 myResultExecPrepare =
> > PQexec(myConnection->conn, seleStmt);
> > (gdb) p seleStmt
> > $1 = "SELECT * FROM T_AM_TERM_BILLING WHERE (TR_STATUS =
> > 'DEFERRED') AND ((DOWNLOAD_DATE < 20070108) OR ((DOWNLOAD_DATE =
> > 20070108) AND (DOWNLOAD_TIME < 203744)))", '\000' <repeats 43 times>
> > (gdb) q
> > The program is running. Quit anyway (and detach it)? (y or n) y
> > Detaching from program: /path/name, process 3587
>
> > From postgres log
>
> > 2007-01-08 20:37:44.839 NZDT ain(at)[local]%smf>LOG: statement:
> > select pg_get_indexdef(indexrelid) from pg_index where ind
> > relid = ( select oid from pg_class where relname =
> > 't_am_registration_db')
> > 2007-01-08 20:37:44.840 NZDT ain(at)[local]%smf>LOG: duration: 0.347 ms
> > 2007-01-08 20:37:44.840 NZDT ain(at)[local]%smf>LOG: statement:
> > SELECT * FROM T_AM_REGISTRATION_DB WHERE (TR_STATUS = 'DEF
> > ERRED') AND ((DOWNLOAD_DATE < 20070108) OR ((DOWNLOAD_DATE =
> > 20070108) AND (DOWNLOAD_TIME < 203744)))
> > 2007-01-08 20:37:44.841 NZDT ain(at)[local]%smf>LOG: duration: 0.792 ms
> > 2007-01-08 20:37:44.841 NZDT ain(at)[local]%smf>LOG: statement:
> > select attname, attnotnull, atttypid, atttypmod, format_ty
> > pe(atttypid, atttypmod) as data_type from pg_attribute where
> > attnum > 0 and atttypid > 0 and attrelid = ( select oid fro
> > m pg_class where relname = 't_am_term_billing') order by attnum
> > 2007-01-08 20:37:44.842 NZDT ain(at)[local]%smf>LOG: duration: 0.778 ms
> > 2007-01-08 20:37:44.842 NZDT ain(at)[local]%smf>LOG: statement:
> > select pg_get_indexdef(indexrelid) from pg_index where ind
> > relid = ( select oid from pg_class where relname =
> > 't_am_term_billing')
> > 2007-01-08 20:37:44.842 NZDT ain(at)[local]%smf>LOG: duration: 0.346 ms
> > 2007-01-08 20:37:44.842 NZDT ain(at)[local]%smf>LOG: statement:
> > SELECT * FROM T_AM_TERM_BILLING WHERE (TR_STATUS = 'DEFERRED') AND
> > ((DOWNLOAD_DATE < 20070108) OR ((DOWNLOAD_DATE = 20070108) AND
> > (DOWNLOAD_TIME < 203744)))
> > 2007-01-08 20:37:44.843 NZDT ain(at)[local]%smf>LOG: duration: 1.165 ms
> > 2007-01-08 20:50:02.026 NZDT @%>LOG: autovacuum: processing
> > database "template1"
> > 2007-01-08 21:50:02.036 NZDT @%>LOG: autovacuum: processing
> > database "smf"
> > 2007-01-08 22:50:02.084 NZDT @%>LOG: autovacuum: processing
> > database "postgres"
> > 2007-01-08 23:50:02.104 NZDT @%>LOG: autovacuum: processing
> > database "template1"
> > 2007-01-09 00:40:01.090 NZDT [unknown](at)%[unknown]>LOG: connection
> > received: host=[local]
> > 2007-01-09 00:40:01.091 NZDT ain(at)[local]%smf>LOG: connection
> > authorized: user=ain database=smf
> > 2007-01-09 00:40:01.093 NZDT ain(at)[local]%smf>LOG: statement:
> > select attname, attnotnull, atttypid, atttypmod, format_ty
> > pe(atttypid, atttypmod) as data_type from pg_attribute where
> > attnum > 0 and atttypid > 0 and attrelid = ( select oid fro
> > m pg_class where relname = 'com_node_host') order by attnum
> > 2007-01-09 00:40:01.097 NZDT ain(at)[local]%smf>LOG: duration: 3.788 ms
>
> > Regards
> > Steve Martin