| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru> |
| Cc: | Stephen Frost <sfrost(at)snowman(dot)net>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Christoph Berg <myon(at)debian(dot)org>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Surjective functional indexes |
| Date: | 2018-02-01 00:10:19 |
| Message-ID: | CANP8+jLYoA0O35gVNUd65WMxwm6NaPuVUB8BEiqo+=pqFzV+iA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 10 January 2018 at 09:54, Konstantin Knizhnik
<k(dot)knizhnik(at)postgrespro(dot)ru> wrote:
> (new version attached)
Why this comment?
Current implementation of projection optimization has to calculate
index expression twice
in case of hit (value of index expression is not changed) and three
times if values are different.
Old + New for check = 2
plus calculate again in index = 3
?
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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