/ Artifact Content
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

## Artifact e4098a4b8962f9596035c3b87a8928a10648acc509f1bb8d6f96413bbf79a1b3:

``````# 2017 April 30
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# Test the HAVING->WHERE optimization.
#

set testdir [file dirname \$argv0]
source \$testdir/tester.tcl
set testprefix having

do_execsql_test 1.0 {
CREATE TABLE t2(c, d);

CREATE TABLE t1(a, b);
INSERT INTO t1 VALUES(1, 1);
INSERT INTO t1 VALUES(2, 2);
INSERT INTO t1 VALUES(1, 3);
INSERT INTO t1 VALUES(2, 4);
INSERT INTO t1 VALUES(1, 5);
INSERT INTO t1 VALUES(2, 6);
} {}

foreach {tn sql res} {
1 "SELECT a, sum(b) FROM t1 GROUP BY a HAVING a=2" {2 12}
2 "SELECT a, sum(b) FROM t1 GROUP BY a HAVING a=2 AND sum(b)>10" {2 12}
3 "SELECT a, sum(b) FROM t1 GROUP BY a HAVING sum(b)>12" {}
} {
do_execsql_test 1.\$tn \$sql \$res
}

# Run an EXPLAIN command for both SQL statements. Return true if
# the outputs are identical, or false otherwise.
#
proc compare_vdbe {sql1 sql2} {
set r1 [list]
set r2 [list]
db eval "explain \$sql1" { lappend r1 \$opcode \$p1 \$p2 \$p3 \$p4 \$p5}
db eval "explain \$sql2" { lappend r2 \$opcode \$p1 \$p2 \$p3 \$p4 \$p5}
return [expr {\$r1==\$r2}]
}

proc do_compare_vdbe_test {tn sql1 sql2 res} {
uplevel [list do_test \$tn [list compare_vdbe \$sql1 \$sql2] \$res]
}

#-------------------------------------------------------------------------
# Test that various statements that are eligible for the optimization
# produce the same VDBE code as optimizing by hand does.
#
foreach {tn sql1 sql2} {
1 "SELECT a, sum(b) FROM t1 GROUP BY a HAVING a=2"
"SELECT a, sum(b) FROM t1 WHERE a=2 GROUP BY a"

2 "SELECT a, sum(b) FROM t1 GROUP BY a HAVING sum(b)>5 AND a=2"
"SELECT a, sum(b) FROM t1 WHERE a=2 GROUP BY a HAVING sum(b)>5"

3 "SELECT a, sum(b) FROM t1 GROUP BY a COLLATE binary HAVING a=2"
"SELECT a, sum(b) FROM t1 WHERE a=2 GROUP BY a COLLATE binary"

5 "SELECT a, sum(b) FROM t1 GROUP BY a COLLATE binary HAVING 0"
"SELECT a, sum(b) FROM t1 WHERE 0 GROUP BY a COLLATE binary"

6 "SELECT count(*) FROM t1,t2 WHERE a=c GROUP BY b, d HAVING b=d"
"SELECT count(*) FROM t1,t2 WHERE a=c AND b=d GROUP BY b, d"

7 {
SELECT count(*) FROM t1,t2 WHERE a=c GROUP BY b, d
HAVING b=d COLLATE nocase
} {
SELECT count(*) FROM t1,t2 WHERE a=c AND b=d COLLATE nocase
GROUP BY b, d
}

8 "SELECT a, sum(b) FROM t1 GROUP BY a||b HAVING substr(a||b, 1, 1)='a'"
"SELECT a, sum(b) FROM t1 WHERE substr(a||b, 1, 1)='a' GROUP BY a||b"
} {
do_compare_vdbe_test 2.\$tn \$sql1 \$sql2 1
}

# The (4) test in the above set used to generate identical bytecode, but
# that is no longer the case.  The byte code is equivalent, though.
#
do_execsql_test 2.4a {
SELECT x,y FROM (
SELECT a AS x, sum(b) AS y FROM t1
GROUP BY a
) WHERE x BETWEEN 2 AND 9999
} {2 12}
do_execsql_test 2.4b {
SELECT x,y FROM (
SELECT a AS x, sum(b) AS y FROM t1
WHERE x BETWEEN 2 AND 9999
GROUP BY a
)
} {2 12}

#-------------------------------------------------------------------------
# 1: Test that the optimization is only applied if the GROUP BY term
#    uses BINARY collation.
#
# 2: Not applied if there is a non-deterministic function in the HAVING
#    term.
#
foreach {tn sql1 sql2} {
1 "SELECT a, sum(b) FROM t1 GROUP BY a COLLATE nocase HAVING a=2"
"SELECT a, sum(b) FROM t1 WHERE a=2 GROUP BY a COLLATE nocase"

2 "SELECT a, sum(b) FROM t1 GROUP BY a HAVING randomblob(a)<X'88'"
"SELECT a, sum(b) FROM t1 WHERE randomblob(a)<X'88' GROUP BY a"
} {
do_compare_vdbe_test 3.\$tn \$sql1 \$sql2 0
}

#-------------------------------------------------------------------------
# Test that non-deterministic functions disqualify a term from being
# moved from the HAVING to WHERE clause.
#
do_execsql_test 4.1 {
CREATE TABLE t3(a, b);
INSERT INTO t3 VALUES(1, 1);
INSERT INTO t3 VALUES(1, 2);
INSERT INTO t3 VALUES(1, 3);
INSERT INTO t3 VALUES(2, 1);
INSERT INTO t3 VALUES(2, 2);
INSERT INTO t3 VALUES(2, 3);
}

proc nondeter {args} {
incr ::nondeter_ret
expr {\$::nondeter_ret % 2}
}
db func nondeter nondeter

set ::nondeter_ret 0
do_execsql_test 4.2 {
SELECT a, sum(b) FROM t3 GROUP BY a HAVING nondeter(a)
} {1 6}

# If the term where moved, the query above would return the same
# result as the following. But it does not.
#
set ::nondeter_ret 0
do_execsql_test 4.3 {
SELECT a, sum(b) FROM t3 WHERE nondeter(a) GROUP BY a
} {1 4 2 2}

finish_test
```
```