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sequential scans on few columns tables

From: Tomasz Myrta <jasiek(at)klaster(dot)net>
To: pgsql-performance(at)postgresql(dot)org
Subject: sequential scans on few columns tables
Date: 2003-06-16 19:49:40
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Lists: pgsql-performance
Recently I was wondering about tables difficult to index. Example - 
queries with "ilike" where clauses. Without additional contrib modules 
the only way to search such tables is sequential scan (am I right?)

The point is too keep these tables as small as possible. We can do this 
by denormalizing tables. Let's say we have table "users" which we split 
into 1:1 relation "users_header" and "users_data". We put searchable 
columns into users_header and rest of them into users_data. users_data 
have some integer foreign key referencing to users_header.

What do you think about it? Does the Postgres use advantages of small 
table users_header? Sequential scan on memory cached table should speed 
up queries, the rest columns are in integer-indexed table which 
shouldn't slow it down.

These example above is ony an idea, I don't have currently any example 
for it.

Tomasz Myrta


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Subject: Re: sequential scans on few columns tables
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Subject: Re: functional indexes instead of regular index on field(s)?

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