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

Artifact 62d943a02f722948f4410ee0b53c3cb39acd7c41afb083df8d7004238fe90a20:


# 2018-06-07
#
# 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.
#
#***********************************************************************
#
# A multi-key index that uses an IN operator on one of the keys other
# than the left-most key is able to abort the IN-operator loop early
# if key terms further to the left do not match.
#
# Call this the "multikey-IN-operator early-out optimization" or
# just "IN-early-out" optimization for short.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix in6

do_test in6-1.1 {
  db eval {
    CREATE TABLE t1(a,b,c,d);
    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 100, 200+x/2, 300+x/5, x FROM c;
    CREATE INDEX t1abc ON t1(a,b,c);
    ANALYZE;
    UPDATE sqlite_stat1 SET stat='1000000 500000 500 50';
    ANALYZE sqlite_master;
  }
  set ::sqlite_search_count 0
  db eval {
    SELECT d FROM t1
     WHERE a=99
       AND b IN (200,205,201,204)
       AND c IN (304,302,309,308);
  }
} {}
do_test in6-1.2 {
  set ::sqlite_search_count
} {0}  ;# Without the IN-early-out optimization, this value would be 15

# The multikey-IN-operator early-out optimization does not apply
# when the IN operator is on the left-most column of the index.
#
do_test in6-1.3 {
  db eval {
    EXPLAIN
    SELECT d FROM t1
      WHERE a IN (98,99,100,101)
        AND b=200 AND c=300;
  }
} {~/(IfNoHope|SeekHit)/}

set sqlite_search_count 0
do_execsql_test in6-1.4 {
 SELECT d FROM t1
  WHERE a=100
    AND b IN (200,201,202,204)
    AND c IN (300,302,301,305)
  ORDER BY +d;
} {1 2 3 4 5 8 9}
do_test in6-1.5 {
  set ::sqlite_search_count
} {39}

do_execsql_test in6-2.1 {
  CREATE TABLE t2(e INT UNIQUE, f TEXT);
  SELECT d, f FROM t1 LEFT JOIN t2 ON (e=d)
  WHERE a=100
    AND b IN (200,201,202,204)
    AND c IN (300,302,301,305)
  ORDER BY +d;
} {1 {} 2 {} 3 {} 4 {} 5 {} 8 {} 9 {}}

finish_test