fix(core): fix bug: The instance occasionally crashes if both fields …

…specified for an equi-join are of the string data types (stoneatom#1476)

mysql-test/suite/tianmu/r/hash_join.result

@@ -0,0 +1,21 @@
+DROP DATABASE IF EXISTS hash_join_test;
+CREATE DATABASE hash_join_test;
+USE hash_join_test;
+CREATE TABLE `test1` (
+`id` varchar(64) NOT NULL COMMENT 'ID'
+) ENGINE=TIANMU DEFAULT CHARSET=utf8mb4;
+CREATE TABLE `test2` (
+`user_id` varchar(32) NOT NULL COMMENT '用户ID'
+) ENGINE=TIANMU DEFAULT CHARSET=utf8;
+insert test1 values('aaa');
+insert test1 values('bbb');
+insert test1 values('ccc');
+insert test2 values('aaa');
+insert test2 values('bbb');
+insert test2 values('ccc');
+select test1.id,test2.user_id  from test2,test1 where test2.user_id = test1.id ;
+id	user_id
+aaa	aaa
+bbb	bbb
+ccc	ccc
+DROP DATABASE hash_join_test;

mysql-test/suite/tianmu/t/hash_join.test

@@ -0,0 +1,29 @@
+--source include/have_tianmu.inc
+
+--disable_warnings
+DROP DATABASE IF EXISTS hash_join_test;
+--enable_warnings
+
+CREATE DATABASE hash_join_test;
+
+USE hash_join_test;
+
+CREATE TABLE `test1` (
+  `id` varchar(64) NOT NULL COMMENT 'ID'
+) ENGINE=TIANMU DEFAULT CHARSET=utf8mb4;
+
+CREATE TABLE `test2` (
+  `user_id` varchar(32) NOT NULL COMMENT '用户ID'
+) ENGINE=TIANMU DEFAULT CHARSET=utf8;
+
+insert test1 values('aaa');
+insert test1 values('bbb');
+insert test1 values('ccc');
+
+insert test2 values('aaa');
+insert test2 values('bbb');
+insert test2 values('ccc');
+
+select test1.id,test2.user_id  from test2,test1 where test2.user_id = test1.id ;
+
+DROP DATABASE hash_join_test;

storage/tianmu/core/parallel_hash_join.cpp

@@ -34,7 +34,10 @@ namespace Tianmu {
 namespace core {
 namespace {
 const int kJoinSplittedMinPacks = 5;
-const int kTraversedPacksPerFragment = 30;
+// bug 1476:  change this threhold from 30 to INT_MAX32 to disable the parallel hash join
+// because the result is sometimes wrong if parallel hash join is enabled.
+// we'll re-enable the hash join later if the bug is fixed in near future.
+const int kTraversedPacksPerFragment = INT_MAX32 / 2;
 
 int EvaluateTraversedFragments(int packs_count) {
   const int kMaxTraversedFragmentCount = 8;