Hi,
Thanks for your suggestions. Here's an output of the explain analyse.
I'll change the shared_buffers and look at the behaviour again.
"Limit (cost=59.53..59.53 rows=1 width=28) (actual time=15.681..15.681
rows=1 loops=1)"
" -> Sort (cost=59.53..59.53 rows=1 width=28) (actual
time=15.678..15.678 rows=1 loops=1)"
" Sort Key: ceil(subq.percentcover), (1::double precision /
ds.maxresolution)"
" -> Hash Join (cost=58.19..59.52 rows=1 width=28) (actual
time=15.630..15.663 rows=2 loops=1)"
" Hash Cond: ("outer".datasetid = "inner".did)"
" -> Seq Scan on tbl_metadata_dataset ds (cost=0.00..1.21
rows=21 width=24) (actual time=0.006..0.021 rows=21 loops=1)"
" -> Hash (cost=58.18..58.18 rows=1 width=12) (actual
time=15.591..15.591 rows=2 loops=1)"
" -> Sort (cost=58.17..58.17 rows=1 width=117)
(actual time=15.585..15.586 rows=2 loops=1)"
" Sort Key: tbl_metadata_chunks.datasetid"
" -> HashAggregate (cost=58.13..58.16 rows=1
width=117) (actual time=15.572..15.573 rows=2 loops=1)"
" -> Hash IN Join (cost=3.34..58.10
rows=7 width=117) (actual time=0.261..0.544 rows=50 loops=1)"
" Hash Cond: ("outer".datasetid =
"inner".datasetid)"
" -> Bitmap Heap Scan on
tbl_metadata_chunks (cost=2.05..56.67 rows=14 width=117) (actual
time=0.204..0.384 rows=60 loops=1)"
" Filter: (chunkgeometry &&
'0103000020E6100000010000000500000058631EDF87ECC1BF608F3D1911694940A0958
A8763C9C1BF535069BA846C494026B5F1284FABB8BFAB1577356E6C494094E1170D33F3B
8BF7700CC99FA68494058631EDF87ECC1BF608F3D1 (..)"
" -> Bitmap Index Scan on
tbl_metadata_chunks_idx3 (cost=0.00..2.05 rows=14 width=0) (actual
time=0.192..0.192 rows=60 loops=1)"
" Index Cond:
(chunkgeometry &&
'0103000020E6100000010000000500000058631EDF87ECC1BF608F3D1911694940A0958
A8763C9C1BF535069BA846C494026B5F1284FABB8BFAB1577356E6C494094E1170D33F3B
8BF7700CC99FA68494058631EDF87ECC (..)"
" -> Hash (cost=1.26..1.26
rows=10 width=4) (actual time=0.037..0.037 rows=10 loops=1)"
" -> Seq Scan on
tbl_metadata_dataset (cost=0.00..1.26 rows=10 width=4) (actual
time=0.005..0.024 rows=10 loops=1)"
" Filter: (typeofdataid
= 1)"
"Total runtime: 15.871 ms"
Gopal
