Hi All,
We are doing some load tests with our application running postgres
8.2.4. At times we see updates on a table taking longer (around
11-16secs) than expected sub-second response time. The table in question
is getting updated constantly through the load tests. In checking the
table size including indexes, they seem to be bloated got it confirmed
after recreating it (stats below). We have autovacuum enabled with
default parameters. I thought autovaccum would avoid bloating issues but
looks like its not aggressive enough. Wondering if table/index bloating
is causing update slowness in over a period of time. Any ideas how to
troubleshoot this further.
No IO waits seen during load tests and cpu usage on the server seem to
be 85% idle. This is a v445 sol10 with 4 cpu box attached to SAN
storage.
Here is the update statement and table/index/instance stats.
shared_buffers=4000MB
max_fsm_pages = 2048000
maintenance_work_mem = 512MB
checkpoint_segments = 128
effective_cache_size = 4000MB
update tablexy set col2=$1,col9=$2, col10=$3,col11=$4,col3=$5 WHERE
ID=$6;
Bloated
relname | relowner | relpages | reltuples
------------------------------+----------+----------+-----------
tablexy | 10 | 207423 | 502627
ix_tablexy_col1_col2 | 10 | 38043 | 502627
ix_tablexy_col3 | 10 | 13944 | 502627
ix_tablexy_col4 | 10 | 17841 | 502627
ix_tablexy_col5 | 10 | 19669 | 502627
ix_tablexy_col6 | 10 | 3865 | 502627
ix_tablexy_col7 | 10 | 12359 | 502627
ix_tablexy_col8_col7 | 10 | 26965 | 502627
ct_tablexy_id_u1 | 10 | 6090 | 502627
Recreating tablexy (compact),
relname | relowner | relpages | reltuples
------------------------------+----------+----------+-----------
tablexy | 10 | 41777 | 501233
ix_tablexy_col3 | 10 | 2137 | 501233
ix_tablexy_col8_col7 | 10 | 4157 | 501233
ix_tablexy_col6 | 10 | 1932 | 501233
ix_tablexy_col7 | 10 | 1935 | 501233
ix_tablexy_col1_col2 | 10 | 1933 | 501233
ix_tablexy_col5 | 10 | 2415 | 501233
ix_tablexy_col6 | 10 | 1377 | 501233
ct_tablexy_id_u1 | 10 | 3046 | 501233
Thanks,
Stalin