From: | rwu(dot)cbnco(dot)com(at)cbnco(dot)com |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | low cardinality column |
Date: | 2003-10-02 17:03:13 |
Message-ID: | 33197.207.164.182.8.1065114193.squirrel@mail.cbnco.com |
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Thread: | |
Lists: | pgsql-performance |
Hi,
I have a select like this:
SELECT MAX(transactionid) FROM cbntransaction WHERE transactiontypeid=0;
in the query:
transactionid is the primary key of cbntransaction table,
But transactiontypeid is a low cardinality column, there're over 100,000
records has the same trnsactiontypeid.
I was trying to create an index on (transactiontypeid, transactionid), but
no luck on that, postgresql will still scan the table.
I'm wondering if there's solution for this query:
Maybe something like if I can partition the table using transactiontypeid,
and do a local index on transactionid on each partition, but I couldnt'
find any doc on postgresql to do that.
Thanks in advance,
rong :-)
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