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diff --git a/mysql-test/include/diff_tables.inc b/mysql-test/include/diff_tables.inc
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+# ==== Purpose ====
+#
+# Check if the two given tables (possibly residing on different
+# master/slave servers) are equal.
+#
+# ==== Usage ====
+#
+# The tables to check are given by the test language variables
+# $diff_table_1 and $diff_table_2.  They must be of the
+# following form:
+#
+#  [master:|slave:]database.table
+#
+# I.e., both database and table must be speicified.  Optionally, you
+# can prefix the name with 'master:' (to read the table on master) or
+# with 'slave:' (to read the table on slave).  If no prefix is given,
+# reads the table from the current connection.  If one of these
+# variables has a prefix, both should have a prefix.
+#
+# ==== Side effects ====
+#
+# - Prints "Comparing tables $diff_table_1 and $diff_tables_2".
+#
+# - If the tables are different, prints the difference in a
+#   system-specific format (unified diff if supported) and generates
+#   an error.
+#
+# - If $diff_table_1 or $diff_table_2 begins with 'master:' or
+#   'slave:', it will stay connected to one of those hosts after
+#   execution.  The host is only guaranteed to remain unchanged if
+#   none of $diff_table_1 or $diff_table_2 begins with 'master:' or
+#   'slave:'.
+#
+# ==== Bugs ====
+#
+# - It is currently not possible to use this for tables that are
+#   supposed to be different, because if the files are different:
+#    - 'diff' produces system-dependent output,
+#    - the output includes the absolute path of the compared files,
+#    - the output includes a timestamp.
+#   To fix that, we'd probably have to use SQL to compute the
+#   symmetric difference between the tables.  I'm not sure how to do
+#   that efficiently.  If we implement this, it would be nice to
+#   compare the table definitions too.
+#
+# - It actually compares the result of "SELECT * FROM table ORDER BY
+#   col1, col2, ..., colN INTO OUTFILE 'file'".  Hence, it is assumed
+#   that the comparison orders for both tables are equal and that two
+#   rows that are equal in the comparison order cannot differ, e.g.,
+#   by character case.
+
+
+# ==== Save both tables to file ====
+
+--echo Comparing tables $diff_table_1 and $diff_table_2
+disable_query_log;
+
+--error 0,1
+--remove_file $MYSQLTEST_VARDIR/tmp/diff_table_1
+--error 0,1
+--remove_file $MYSQLTEST_VARDIR/tmp/diff_table_2
+
+let $_diff_table=$diff_table_2;
+let $_diff_i=2;
+while ($_diff_i) {
+
+  # Parse out any leading "master:" or "slave:" from the table
+  # specification and connect the appropriate server.
+  let $_diff_conn_master=`SELECT SUBSTR('$_diff_table', 1, 7) = 'master:'`;
+  if ($_diff_conn_master) {
+    let $_diff_table=`SELECT SUBSTR('$_diff_table', 8)`;
+    connection master;
+  }
+  let $_diff_conn_slave=`SELECT SUBSTR('$_diff_table', 1, 6) = 'slave:'`;
+  if ($_diff_conn_slave) {
+    let $_diff_table=`SELECT SUBSTR('$_diff_table', 7)`;
+    connection slave;
+  }
+
+  # Sanity-check the input.
+  let $_diff_error= `SELECT '$_diff_table' NOT LIKE '_%._%'`;
+  if ($_diff_error) {
+    --echo !!!ERROR IN TEST: \$diff_table_$_diff_i='$_diff_table' is not in the form database.table
+    exit;
+  }
+
+  # We need the output files to be sorted (so that diff_files does not
+  # think the files are different just because they are differently
+  # ordered).  To this end, we first generate a query that sorts the
+  # table by all columns.  Since ORDER BY accept column indices, we
+  # just generate a comma-separated list of all numbers from 1 to the
+  # number of columns in the table.
+  let $_diff_column_index=`SELECT MAX(ordinal_position)
+                           FROM information_schema.columns
+                           WHERE CONCAT(table_schema, '.', table_name) =
+                                 '$_diff_table'`;
+  let $_diff_column_list=$_diff_column_index;
+  dec $_diff_column_index;
+  while ($_diff_column_index) {
+    let $_diff_column_list=$_diff_column_index, $_diff_column_list;
+    dec $_diff_column_index;
+  }
+
+  # Now that we have the comma-separated list of columns, we can write
+  # the table to a file.
+  eval SELECT * FROM $_diff_table ORDER BY $_diff_column_list
+              INTO OUTFILE '$MYSQLTEST_VARDIR/tmp/diff_table_$_diff_i';
+
+  # Do the same for $diff_table_1.
+  dec $_diff_i;
+  let $_diff_table=$diff_table_1;
+}
+
+
+# ==== Compare the generated files ====
+
+diff_files $MYSQLTEST_VARDIR/tmp/diff_table_1 $MYSQLTEST_VARDIR/tmp/diff_table_2;
+
+--remove_file $MYSQLTEST_VARDIR/tmp/diff_table_1
+--remove_file $MYSQLTEST_VARDIR/tmp/diff_table_2
+
+enable_query_log;