expression: fix painc on substring_index (pingcap#7806)

zz-jason · Oct 15, 2018 · f336d90 · f336d90
1 parent 44cb05f
commit f336d90
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Showing 2 changed files with 6 additions and 0 deletions.
diff --git a/expression/builtin_string.go b/expression/builtin_string.go
@@ -1209,6 +1209,11 @@ func (b *builtinSubstringIndexSig) evalString(row types.Row) (d string, isNull b
 	} else {
 		// If count is negative, everything to the right of the final delimiter (counting from the right) is returned.
 		count = -count
+		if count < 0 {
+			// -count overflows max int64, returns an empty string.
+			return "", false, nil
+		}
+
 		if count < end {
 			start = end - count
 		}

diff --git a/expression/integration_test.go b/expression/integration_test.go
@@ -736,6 +736,7 @@ func (s *testIntegrationSuite) TestStringBuiltin(c *C) {
 	result.Check(testkit.Rows("www.pingcap 12345 45 2017 01:01"))
 	result = tk.MustQuery(`select substring_index('www.pingcap.com', '.', 0), substring_index('www.pingcap.com', '.', 100), substring_index('www.pingcap.com', '.', -100)`)
 	result.Check(testkit.Rows(" www.pingcap.com www.pingcap.com"))
+	tk.MustQuery(`select substring_index('xyz', 'abc', 9223372036854775808)`).Check(testkit.Rows(``))
 	result = tk.MustQuery(`select substring_index('www.pingcap.com', 'd', 1), substring_index('www.pingcap.com', '', 1), substring_index('', '.', 1)`)
 	result.Check(testutil.RowsWithSep(",", "www.pingcap.com,,"))
 	result = tk.MustQuery(`select substring_index(null, '.', 1), substring_index('www.pingcap.com', null, 1), substring_index('www.pingcap.com', '.', null)`)