expression: fix painc on substring_index (#7806) (#7896)

pingcap · Oct 15, 2018 · 0b4762c · 0b4762c
1 parent 2af0f18
commit 0b4762c
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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)`)