Experimental change to support the covering index optimization for queries with OR terms in the WHERE clause that search a single index more than once.

FossilOrigin-Name: 1dc8c7c741a82bb98a07f3fdb8142d8bc8d8a98b

test/whereD.test

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+# 2012 August 24
+#
+# 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 testing that an index may be used as a covering
+# index when there are OR expressions in the WHERE clause. 
+#
+
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set ::testprefix whereD
+
+do_execsql_test 1.1 {
+  CREATE TABLE t(i,j,k);
+  CREATE INDEX i ON t(i,j,k);
+
+  INSERT INTO t VALUES(3, 3, 'three');
+  INSERT INTO t VALUES(2, 2, 'two');
+  INSERT INTO t VALUES(1, 1, 'one');
+  INSERT INTO t VALUES(4, 4, 'four');
+}
+
+do_execsql_test 1.2 {
+  SELECT k FROM t WHERE (i=1 AND j=1) OR (i=2 AND j=2);
+} {one two}
+
+finish_test
+