New optimizations to detect early when queries return no rows due to

tables being empty.  This includes the EXISTS-to-JOIN optimization that
tries to transform EXISTS constraints into additional terms of the FROM
clause.

FossilOrigin-Name: e33da6d5dc964db817d1bc63c9083aecd93d49ee14d5198600b47eaf7c5b9331

1 files changed, 49 insertions, 0 deletions

diff --git a/test/existsfault.test b/test/existsfault.test
new file mode 100644
index 000000000..4b335d84c
--- /dev/null
+++ b/test/existsfault.test
@@ -0,0 +1,49 @@
+# 2024 May 25
+#
+# 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.
+#
+#***********************************************************************
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+source $testdir/lock_common.tcl
+source $testdir/malloc_common.tcl
+set testprefix existsfault
+
+db close
+sqlite3_shutdown
+sqlite3_config_lookaside 0 0
+sqlite3_initialize
+autoinstall_test_functions
+sqlite3 db test.db
+
+do_execsql_test 1.0 {
+  CREATE TABLE x1(a, b);
+  INSERT INTO x1 VALUES(1, 2), (3, 4), (5, 6);
+  CREATE UNIQUE INDEX x1a ON x1(a);
+  CREATE INDEX x1b ON x1(b);
+
+  CREATE TABLE x2(x, y);
+  INSERT INTO x2 VALUES(1, 2), (3, 4), (5, 6);
+}
+
+do_faultsim_test 1 -faults oom* -prep {
+  sqlite3 db test.db
+  execsql { SELECT * FROM sqlite_schema }
+} -body {
+  execsql {
+    SELECT count(*) FROM x2 WHERE EXISTS (SELECT 1 FROM x1 WHERE a=x) AND y!=11
+  }
+} -test {
+  faultsim_test_result {0 3}
+}
+
+finish_test
+
+