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Partitions and max_locks_per_transaction

From: Hrishikesh (हृषीकेश मेहेंदळ <hashinclude(at)gmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Partitions and max_locks_per_transaction
Date: 2009-11-20 01:22:56
Message-ID: a7c00d4b0911191722l4354168ajfd06f6cc7cc1ed82@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
Hi All,

I have a stats collection system where I collect stats at specific
intervals (from network monitoring nodes), and stuff them into a
PostgreSQL DB. To make make the retrieval faster, I'm using a
partitioning scheme as follows:

stats_300: data gathered at 5 mins, child tables named stats_300_t1_t2
(where t2 - t1 = 2 hrs), i.e. 12 tables in one day
stats_3600: data gathered / calculated over 1 hour, child tables
similar to the above - stats_3600_t1_t2, where (t2 - t1) is 2 days
(i.e. 15 tables a month)
stats_86400: data gathered / calculated over 1 day, stored as
stats_86400_t1_t2 where (t2 - t1) is 30 days (i.e. 12 tables a year).

The child tables have 4 indexes each (including a unique index, also
used for CLUSTER). No indexes are defined on the parent tables. Data
insert / load happens directly to the child table (no stored procs
involved).

I'm running into the error "ERROR:  out of shared memory HINT:  You
might need to increase max_locks_per_transaction. ". Looking back, it
seems acceptable to have max_locks in the thousands (with a
corresponding shared_buffers setting so I don't overflow SHMMAX).
However, what I find strange is that I only have 32 tables so far
(some at 5-min, some at 1-hour). I'm doing some data preloading, and
even that ran into this problem. I'm running this on a shared server
with 4GB total RAM, so I don't want PG to use too much. (Eventually,
the system is designed to have

I tried increasing the max_locks_per_transaction, but that just seems
to delay the inevitable.

Any ideas what I might be doing wrong? If this may be a programmatic
issue, I'm using Python PygreSQL to load the data as prepared
statements. I have one connection to the DB, create and release a
cursor, and commit transactions when I'm done.

--- begin postgresql.conf ---
data_directory = '/data/pg'
hba_file = '/etc/pg_hba.conf'
ident_file = '/etc/pg_ident.conf'
external_pid_file = '/data/pg/8.4-main.pid'
port = 5432
max_connections = 8
unix_socket_directory = '/tmp'
ssl = false
shared_buffers = 128MB # used to be 500
work_mem = 64MB
maintenance_work_mem = 64MB
wal_buffers = 1MB
checkpoint_segments = 30
checkpoint_timeout = 15min
effective_cache_size = 1024MB
default_statistics_target = 800
constraint_exclusion = on
log_destination = 'syslog'
syslog_facility = 'LOCAL1'
syslog_ident = 'postgres'
client_min_messages = error
log_min_messages = error
log_line_prefix = '%t '
log_temp_files = 0
datestyle = 'iso, mdy'
lc_messages = 'C'
lc_monetary = 'C'
lc_numeric = 'C'
lc_time = 'C'
default_text_search_config = 'pg_catalog.english'
max_locks_per_transaction = 8000 # Originally 500, tried 1k and 2k also

Thanks
Hrishikesh

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