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Update some comments to use SQL examples rather than QUEL. From Simon

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Riggs.
This commit is contained in:
Neil Conway
2005-04-24 11:46:21 +00:00
parent a7f2a788ee
commit 947eb97560
2 changed files with 9 additions and 10 deletions
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15
src/backend/executor/nodeResult.c
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@ -8,15 +8,13 @@
* Result nodes are used in queries where no relations are scanned.
* Examples of such queries are:
*
* retrieve (x = 1)
* and
* append emp (name = "mike", salary = 15000)
* select 1 * 2
*
* Result nodes are also used to optimise queries with constant
* qualifications (ie, quals that do not depend on the scanned data),
* such as:
*
* retrieve (emp.all) where 2 > 1
* select * from emp where 2 > 1
*
* In this case, the plan generated is
*
@ -24,9 +22,10 @@
* /
* SeqScan (emp.all)
*
* At runtime, the Result node evaluates the constant qual once.
* If it's false, we can return an empty result set without running
* the controlled plan at all. If it's true, we run the controlled
* At runtime, the Result node evaluates the constant qual once,
* which is shown by EXPLAIN as a One-Time Filter. If it's
* false, we can return an empty result set without running the
* controlled plan at all. If it's true, we run the controlled
* plan normally and pass back the results.
*
*
@ -34,7 +33,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeResult.c,v 1.29 2004/12/31 21:59:45 pgsql Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeResult.c,v 1.30 2005/04/24 11:46:21 neilc Exp $
*
*-------------------------------------------------------------------------
*/