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Re: queries and inserts

From: "Mitch Vincent" <mitch(at)venux(dot)net>
To: "Rini Dutta" <rinid(at)rocketmail(dot)com>, <pgsql-sql(at)hub(dot)org>
Cc: <pgsql-hackers(at)hub(dot)org>
Subject: Re: queries and inserts
Date: 2000-08-27 22:01:02
Message-ID: 012401c01072$4ace15b0$0200000a@doot (view raw, whole thread or download thread mbox)
Lists: pgsql-hackerspgsql-sql
Removing indexes will speed up the INSERT portion but slow down the SELECT

Just an FYI, you can INSERT into table (select whatever from another
table) -- you could probably do what you need in a single query (but would
also probably still have the speed problem).

Have you EXPLAINed the SELECT query to see if index scans are being used
where possible?


----- Original Message -----
From: "Rini Dutta" <rinid(at)rocketmail(dot)com>
To: <pgsql-sql(at)hub(dot)org>
Cc: <pgsql-hackers(at)hub(dot)org>
Sent: Friday, August 25, 2000 12:20 PM
Subject: [SQL] queries and inserts

> Hi,
> I am interested in how to speed up storage. About 1000
> or more inserts may need to be performed at a time ,
> and before each insert I need to look up its key from
> the reference table. So each insert is actually a
> query followed by an insert.
> The tables concerned are :
> CREATE TABLE referencetable(idx serial, rcol1 int4 NOT
> NULL, rcol2 int4 NOT  NULL, rcol3 varchar(20) NOT
> NULL, rcol4 varchar(20), PRIMARY KEY(idx) ...
> CREATE INDEX index_referencetable on
> referencetable(rcol1, rcol2, rcol3, rcol4);
> CREATE TABLE datatable ( ref_idx int4,
> start_date_offset int4 NOT NULL, stop_date_offset int4
> NOT NULL, dcol4 float NOT NULL, dcol5  float NOT NULL,
> PRIMARY KEY(ref_idx, start_date_offset), CONSTRAINT c1
> FOREIGN KEY(ref_idx) REFERENCES referencetable(idx) );
> I need to do the following sequence n number of times
> -
> 1. select idx (as key) from referencetable where
> col1=c1 and col2=c2 and col3=c3 and col4=c4; (Would an
> initial 'select into temptable'  help here since for a
> large number of these queries 'c1' and 'c2'
> comnbinations would remain constant ?)
> 2. insert into datatable values(key, ....);
> I am using JDBC interface of postgresql-7.0.2 on
> Linux. 'referencetable' has about 1000 records, it can
> keep growing. 'datatable' has about 3 million records,
> it would grow at a very fast rate. Storing 2000
> records takes around 75 seconds after I vacuum
> analyze. (before that it took around 40 seconds - ???)
> . I am performing all the inserts ( including the
> lookup) as one transaction.
> Thanks,
> Rini
> __________________________________________________
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> Yahoo! Mail - Free email you can access from anywhere!

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