Allow sub-queries that use UNION ALL to be flattened, even if the parent query is a join. Still some problems on this branch.

FossilOrigin-Name: 00e4bf74d3dfb87666a2266905f7d1a2afc6eb088d22cfd4f38f048733d6b936

test/selectC.test

@@ -261,10 +261,10 @@ do_execsql_test 5.2 {
 }
 
 do_execsql_test 5.3 {
-  SELECT * FROM x1, (SELECT b FROM vvv UNION ALL SELECT c from x3);
+  SELECT * FROM x1, (SELECT b FROM vvv UNION ALL SELECT c from x3) ORDER BY 1,2;
 } {
-  a 21 a 22 a 23 a 24 a 25 a 302 a 303 a 301
-  b 21 b 22 b 23 b 24 b 25 b 302 b 303 b 301
+  a 21 a 22 a 23 a 24 a 25 a 301 a 302 a 303
+  b 21 b 22 b 23 b 24 b 25 b 301 b 302 b 303
 }
 
 finish_test

test/unionall.test

@@ -0,0 +1,58 @@
+# 2020-12-16
+#
+# 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.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is flattening UNION ALL sub-queries.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix unionall
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1_a(a INTEGER PRIMARY KEY, b TEXT);
+  CREATE TABLE t1_b(c INTEGER PRIMARY KEY, d TEXT);
+  CREATE TABLE t1_c(e INTEGER PRIMARY KEY, f TEXT);
+
+  INSERT INTO t1_a VALUES(1, 'one'), (4, 'four');
+  INSERT INTO t1_b VALUES(2, 'two'), (5, 'five');
+  INSERT INTO t1_c VALUES(3, 'three'), (6, 'six');
+
+  CREATE VIEW t1 AS 
+    SELECT a, b FROM t1_a   UNION ALL
+    SELECT c, d FROM t1_b   UNION ALL
+    SELECT e, f FROM t1_c;
+
+  CREATE TABLE i1(x);
+  INSERT INTO i1 VALUES(2), (5), (6), (1);
+}
+
+do_execsql_test 1.1 {
+  SELECT a, b FROM (
+    SELECT a, b FROM t1_a   UNION ALL
+    SELECT c, d FROM t1_b   UNION ALL
+    SELECT e, f FROM t1_c
+  ) ORDER BY a
+} {
+  1 one 2 two 3 three 4 four 5 five 6 six
+}
+
+do_execsql_test 1.2 {
+  SELECT a, b FROM t1 ORDER BY a
+} {
+  1 one 2 two 3 three 4 four 5 five 6 six
+}
+
+do_execsql_test 1.3 {
+  SELECT a, b FROM i1, t1 WHERE a=x ORDER BY a
+} {1 one 2 two 5 five 6 six}
+
+
+finish_test

test/unionallfault.test

@@ -0,0 +1,36 @@
+# 2020-12-16
+#
+# 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
+set testprefix unionallfault
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x,y,z);
+  CREATE TABLE t3(x,y,z);
+}
+faultsim_save_and_close
+
+
+do_faultsim_test 1 -faults oom-t* -prep {
+  faultsim_restore_and_reopen
+} -body {
+  execsql {
+    SELECT * FROM (
+      SELECT x FROM t1 UNION ALL SELECT y FROM t1
+    )
+  }
+} -test {
+  faultsim_test_result {0 {}}
+}
+
+finish_test

test/whereL.test

@@ -26,14 +26,13 @@ do_eqp_test 110 {
   SELECT * FROM t1, v4 WHERE t1.a=?1 AND v4.a=t1.a;
 } {
   QUERY PLAN
-  |--MATERIALIZE xxxxxx
-  |  `--COMPOUND QUERY
-  |     |--LEFT-MOST SUBQUERY
-  |     |  `--SEARCH TABLE t2 USING INDEX sqlite_autoindex_t2_1 (a=?)
-  |     `--UNION ALL
-  |        `--SEARCH TABLE t3 USING INDEX sqlite_autoindex_t3_1 (a=?)
-  |--SCAN SUBQUERY xxxxxx
-  `--SEARCH TABLE t1 USING INDEX sqlite_autoindex_t1_1 (a=?)
+  `--COMPOUND QUERY
+     |--LEFT-MOST SUBQUERY
+     |  |--SEARCH TABLE t2 USING INDEX sqlite_autoindex_t2_1 (a=?)
+     |  `--SEARCH TABLE t1 USING INDEX sqlite_autoindex_t1_1 (a=?)
+     `--UNION ALL
+        |--SEARCH TABLE t3 USING INDEX sqlite_autoindex_t3_1 (a=?)
+        `--SEARCH TABLE t1 USING INDEX sqlite_autoindex_t1_1 (a=?)
 }
 
 # The scan of the t1 table goes first since that enables the ORDER BY