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# 2012 September 17
#
# 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.
#
#***********************************************************************
#
# Tests for the optimization which attempts to use a covering index
# for a full-table scan (under the theory that the index will be smaller
# and require less I/O and hence will run faster.)
#
set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix coveridxscan
do_test 1.1 {
db eval {
CREATE TABLE t1(a,b,c);
INSERT INTO t1 VALUES(5,4,3), (4,8,2), (3,2,1);
CREATE INDEX t1ab ON t1(a,b);
CREATE INDEX t1b ON t1(b);
SELECT a FROM t1;
}
# covering index used for the scan, hence values are increasing
} {3 4 5}
do_test 1.2 {
db eval {
SELECT a, c FROM t1;
}
# There is no covering index, hence the values are in rowid order
} {5 3 4 2 3 1}
do_test 1.3 {
db eval {
SELECT b FROM t1;
}
# Choice of two indices: use the one with fewest columns
} {2 4 8}
do_test 2.1 {
optimization_control db cover-idx-scan 0
db eval {SELECT a FROM t1}
# With the optimization turned off, output in rowid order
} {5 4 3}
do_test 2.2 {
db eval {SELECT a, c FROM t1}
} {5 3 4 2 3 1}
do_test 2.3 {
db eval {SELECT b FROM t1}
} {4 8 2}
db close
sqlite3_shutdown
sqlite3_config_cis 0
sqlite3 db test.db
do_test 3.1 {
db eval {SELECT a FROM t1}
# With the optimization configured off, output in rowid order
} {5 4 3}
do_test 3.2 {
db eval {SELECT a, c FROM t1}
} {5 3 4 2 3 1}
do_test 3.3 {
db eval {SELECT b FROM t1}
} {4 8 2}
db close
sqlite3_shutdown
sqlite3_config_cis 1
sqlite3 db test.db
# The CIS optimization is enabled again. Covering indices are once again
# used for all table scans.
do_test 4.1 {
db eval {SELECT a FROM t1}
} {3 4 5}
do_test 4.2 {
db eval {SELECT a, c FROM t1}
} {5 3 4 2 3 1}
do_test 4.3 {
db eval {SELECT b FROM t1}
} {2 4 8}
finish_test
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