<html><body><span style="font-family:Verdana; color:#000000; font-size:10pt;"><div>We are having performance related problems on one of our big data Partition tables. The table is partitioned by date and the partitions are organized from Jan 2003 thru Dec 2013. <BR>We have 268 child partitions associated with the Parent table, and we have constraint_exclusion=partition set. </div>
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<div>The execution of the SQL query: select count(*) from dna_strands; </div>
<div>yields: QUERY PLAN<BR>_____________________________________________________________________________________________ </div>
<div>Aggregate (cost=2246778.49..2246778.50 rows=1 width=0)<BR> -> Append (0.00..2159647.04 rows=34852580 width=0)<BR> -> Seq Scan on dna_strands (cost=0.00..0.00 rows=1 width)<BR> Filter: (cid = 1)<BR> -> Index Scan using dna_strands_y2003m01_cid on dna_strands_y2003m01 dna_strands (cost=0.00..677652 rows=1 width=0)<BR> Index Cond: (cid = 1)<BR> -> Index Scan using dna_strands_y2003m02_cid on dna_strands_y2003m02 dna_strands (cost=0.00..974423 rows=1 width=0)<BR> Index Cond: (cid = 1)<BR> -> Index Scan using dna_strands_y2003m03_cid on dna_strands_y2003m03 dna_strands (cost=0.00..992301 rows=1 width=0)<BR> Index Cond: (cid = 1)<BR> ...<BR> ...</div>
<div> ...</div>
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<div> -> Index Scan using dna_strands_y2013m12_cid on dna_strands_y2013m12 dna_strands (cost=0.00..8.27 rows=1 width=0)<BR> Index Cond: (cid = 1)</div>
<div>Question: Is there any way to modify the Planner to do the inverse of the Index Scan's. In other words, to start the index scans in reverse order from <BR>the most recent date to the oldest date, i.e. "dna_strands_y2013m12" backwards. Our application users query much more heavily at the most recent data that <BR>has been ingested into the PostgreSQL database. Would this capability speed up query performance?</div>
<div>Thanks</div>
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