Evaluate expressions only once when the same expression is used in both the

result set and in the ORDER BY clause.

FossilOrigin-Name: c2f3bbad778504681b39ab9399a1eb3c1a35ab3f

test/orderby9.test

@@ -0,0 +1,52 @@
+# 2015-08-26
+#
+# 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.
+# 
+# This file seeks to verify that expressions (and especially functions)
+# that are in both the ORDER BY clause and the result set are only
+# evaluated once.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set ::testprefix orderby9
+
+
+do_execsql_test setup {
+  -- create a table with many entries
+  CREATE TABLE t1(x);
+  WITH RECURSIVE
+     c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100)
+  INSERT INTO t1 SELECT x FROM c;
+}
+do_test 1.0 {
+  set l1 {}
+  # If random() is only evaluated once and then reused for each row, then
+  # the output should appear in sorted order.  If random() is evaluated 
+  # separately for the result set and the ORDER BY clause, then the output
+  # order will be random.
+  db eval {SELECT random() AS y FROM t1 ORDER BY 1;} {lappend l1 $y}
+  expr {$l1==[lsort -int $l1]}
+} {1}
+
+do_test 1.1 {
+  set l1 {}
+  db eval {SELECT random() AS y FROM t1 ORDER BY random();} {lappend l1 $y}
+  expr {$l1==[lsort -int $l1]}
+} {1}
+
+do_test 1.2 {
+  set l1 {}
+  db eval {SELECT random() AS y FROM t1 ORDER BY +random();} {lappend l1 $y}
+  expr {$l1==[lsort -int $l1]}
+} {0}
+
+finish_test