Re: Relation extension scalability

On Wed, Feb 10, 2016 at 3:24 PM, Andres Freund <andres@anarazel.de> wrote:

I have quickly measured the per transaction latency of one case
(I selected below case to find the worst case latency because in this case
we are extending by 1000 blocks and data doesn't fits in shared buffer)

Test--2 (big record insert and Data doesn't fits in shared Buffer)
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./psql -d postgres -c "create table test_data(a int, b text)"
./psql -d postgres -c "insert into test_data values(generate_series(1,1000),repeat('x', 1024))"
./psql -d postgres -c "create table data (a int) with(extend_by_blocks=1000)"
echo "insert into data select * from test_data;" >> copy_script

 shared_buffers=512B -c max_wal_size=20GB -c checkpoint_timeout=10min
./pgbench -c 8 -j 8 -f copy_script -T -l 120 postgres

                    base         patch(extend 1000)
best             23245          3857
worst          236329     382859
Average     190303       35143

I have also attached the pgbench log files
 patch_1000.tar --> log files with patch extend by 1000 blocks
 base.tar --> log files with base code

From attached files we can see that very few transactions latency with patch is high(> 300,000) which is expected and that too when we are
extensing 1000 blocks, And we base code almost every transaction latency is hight (>200,000) that we can see that best case and average case latency is 1/5 with extend by 1000.

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