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+# 2017-02-15
+#
+# 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 cases to show that a join involving an empty table is very fast.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+
+# Build some test data
+#
+do_execsql_test emptytable-100 {
+ CREATE TABLE t1(a);
+ WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100)
+ INSERT INTO t1(a) SELECT x FROM c;
+ CREATE TABLE empty(x);
+ SELECT count(*) FROM t1;
+} {100}
+
+# Interrupt queries after 1M cycles to prevent burning excess CPU
+proc stopDb {args} {
+ db interrupt
+}
+db progress 1000000 {stopDb}
+
+# Prior to the query planner optimization on 2017-02-15, this query would
+# take a ridiculous amount of time. If that optimization stops working,
+# the result here will be in interrupt for running too long.
+#
+do_catchsql_test emptytable-110 {
+ SELECT count(*) FROM t1, t1, t1, t1, t1, t1, empty;
+} {0 0}
+
+do_catchsql_test emptytable-120 {
+ SELECT count(*) FROM t1, t1 LEFT JOIN empty;
+} {0 10000}
+do_catchsql_test emptytable-121 {
+ SELECT count(*) FROM t1, t1 LEFT JOIN t1, empty;
+} {0 0}
+
+
+finish_test