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Implement FROM-clause subqueries as co-routines whenever they are guaranteed

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to be the outer-most loop of the join.

FossilOrigin-Name: c7bae50bdccb5bcf3bc22e8ac5bb6725ef13db39
This commit is contained in:
drh
2016-03-15 17:52:12 +00:00
parent 82f525406a
commit 0ff47e9e1b
4 changed files with 61 additions and 12 deletions
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37
test/select4.test
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@ -12,7 +12,6 @@
# focus of this file is testing UNION, INTERSECT and EXCEPT operators
# in SELECT statements.
#
# $Id: select4.test,v 1.30 2009/04/16 00:24:24 drh Exp $
set testdir [file dirname $argv0]
source $testdir/tester.tcl
@ -936,4 +935,40 @@ do_execsql_test select4-15.1 {
ORDER BY 1;
} {1 33 456 2 33 789}
# Enhancement (2016-03-15): Use a co-routine for subqueries if the
# subquery is guaranteed to be the outer-most query
#
do_execsql_test select4-16.1 {
DROP TABLE IF EXISTS t1;
CREATE TABLE t1(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,
PRIMARY KEY(a,b DESC)) WITHOUT ROWID;
WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100)
INSERT INTO t1(a,b,c,d)
SELECT x%10, x/10, x, printf('xyz%dabc',x) FROM c;
SELECT t3.c FROM
(SELECT a,max(b) AS m FROM t1 WHERE a>=5 GROUP BY a) AS t2
JOIN t1 AS t3
WHERE t2.a=t3.a AND t2.m=t3.b
ORDER BY t3.a;
} {95 96 97 98 99}
do_execsql_test select4-16.2 {
SELECT t3.c FROM
(SELECT a,max(b) AS m FROM t1 WHERE a>=5 GROUP BY a) AS t2
CROSS JOIN t1 AS t3
WHERE t2.a=t3.a AND t2.m=t3.b
ORDER BY t3.a;
} {95 96 97 98 99}
do_execsql_test select4-16.3 {
SELECT t3.c FROM
(SELECT a,max(b) AS m FROM t1 WHERE a>=5 GROUP BY a) AS t2
LEFT JOIN t1 AS t3
WHERE t2.a=t3.a AND t2.m=t3.b
ORDER BY t3.a;
} {95 96 97 98 99}
finish_test