Re: Simple Column reordering - Mailing list pgsql-hackers
From | Bruce Momjian |
---|---|
Subject | Re: Simple Column reordering |
Date | |
Msg-id | 200702261620.l1QGKJA03363@momjian.us Whole thread Raw |
In response to | Simple Column reordering ("Simon Riggs" <simon@2ndquadrant.com>) |
Responses |
Re: Simple Column reordering
(Andrew Dunstan <andrew@dunslane.net>)
Re: Simple Column reordering ("Simon Riggs" <simon@2ndquadrant.com>) |
List | pgsql-hackers |
I realized this proposal has been withdrawn, but the fact the proposal even illicited comments exploring it requires me to comment. Folks, how can we entertain ideas that would break SELECT * and no-column-list INSERTs for a small performance boost? If there was no other way to get the performance boost, and the features was rarely used, we might consider such a change, but neither is true in this case. My point is that this proposal is so far away from our acceptable criteria that I am worried about how people are analyzing proposals. --------------------------------------------------------------------------- Simon Riggs wrote: > Column storage position is the subject of many long threads in recent > times. Solutions proposed for this have been both fairly complex and > long enough that nothing seems likely to happen for 8.3. If I'm wrong, > then of course this proposal would be superceded. > > I propose that at CREATE TABLE time, the column ordering is re-ordered > so that the table columns are packed more efficiently. This would be a > physical re-ordering, so that SELECT * and COPY without explicit column > definitions would differ from the original CREATE TABLE statement. > > This would be an optional feature, off by default, controlled by a > USERSET GUC > optimize_column_order = off (default) | on > > When the full column ordering proposal is implemented, > optimize_column_ordering would be set to default to on. The feature > would be supported for at least one more release after this to allow bug > analysis. > > The proposed ordering would be: > 1. All fixed length columns, arranged so that alignment is efficient > 2. All variable length columns > > All column ordering would stay as close as possible to original order > > No changes would be made apart from at CREATE TABLE time. > > The ordering would be repeatable, so that the order would not change on > repeated dump/restore of a table with no changes. > > -- > Simon Riggs > EnterpriseDB http://www.enterprisedb.com > > > > ---------------------------(end of broadcast)--------------------------- > TIP 1: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly -- 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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