Re: GIN improvements part 1: additional information - Mailing list pgsql-hackers

From Alvaro Herrera
Subject Re: GIN improvements part 1: additional information
Date
Msg-id 20131220194359.GE22570@eldon.alvh.no-ip.org
Whole thread Raw
In response to Re: GIN improvements part 1: additional information  (Heikki Linnakangas <hlinnakangas@vmware.com>)
Responses Re: GIN improvements part 1: additional information
List pgsql-hackers
Heikki Linnakangas escribió:

> I believe that eliminates all encodings in the Simple family, as
> well as PForDelta, and surprisingly also Rice encoding. For example,
> if you have three items in consecutive offsets, the differences
> between them are encoded as 11 in rice encoding. If you remove the
> middle item, the encoding for the next item becomes 010, which takes
> more space than the original.

I don't understand this.  If you have three consecutive entries, and the
differences between them are 11, you need to store two 11s.  But if you
have two items, you only need to store 010 once.  So the difference is
larger, but since you need to store only one of them then overall it's
still shorter than the original.  No?

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services



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