Re: TOAST usage setting - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: TOAST usage setting
Date
Msg-id 200705291700.l4TH0vf05481@momjian.us
Whole thread Raw
In response to Re: TOAST usage setting  (Gregory Stark <stark@enterprisedb.com>)
Responses Re: TOAST usage setting  (Gregory Stark <stark@enterprisedb.com>)
List pgsql-hackers
Gregory Stark wrote:
> "Bruce Momjian" <bruce@momjian.us> writes:
> 
> > Gregory Stark wrote:
> >
> >> Is your database initialized with C locale? If so then length(text) is
> >> optimized to not have to detoast:
> >> 
> >>     if (pg_database_encoding_max_length() == 1)
> >>         PG_RETURN_INT32(toast_raw_datum_size(str) - VARHDRSZ);
> >
> > Wow, we optimized length().  OK, will run the test with
> > substring(t,1,1).
> 
> No, we did substring() too :)

Uh, I looked at text_substring(), and while there is an optimization to
do character counting for encoding length == 1, it is still accessing
the data.

--  Bruce Momjian  <bruce@momjian.us>          http://momjian.us EnterpriseDB
http://www.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +


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