Bug#18383169: QUERIES WITH RANDOM_BYTES() ENTER QUERY CACHE

The problem was that queries using RANDOM_BYTES, AES_ENCRYPT
or AES_DECRYPT could be cached in the query cache. RANDOM_BYTES
is random and AES_* are dependent on block_encryption_mode system
variable.

This patch fixes the problem by tagging queries using these functions
as unsafe to cache.

Author: jhauglid

mysql-test/r/query_cache.result

@@ -1811,3 +1811,23 @@ Level	Code	Message
 
 DROP TABLE t1;
 SET SESSION query_cache_type=@qc_type;
+#
+# Bug#18383169: QUERIES WITH RANDOM_BYTES() ENTER QUERY CACHE
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (1);
+FLUSH STATUS;
+# Test that RANDOM_BYTES queries are not cached
+SELECT * FROM t1 WHERE RANDOM_BYTES(16);
+a
+SHOW STATUS LIKE 'Qcache_not_cached';
+Variable_name	Value
+Qcache_not_cached	1
+# same with AES_ENCRYPT
+SELECT * FROM t1 WHERE AES_ENCRYPT('a','a');
+a
+SHOW STATUS LIKE 'Qcache_not_cached';
+Variable_name	Value
+Qcache_not_cached	2
+DROP TABLE t1;
+FLUSH STATUS;

mysql-test/t/query_cache.test

@@ -1419,3 +1419,22 @@ SHOW WARNINGS;
 DROP TABLE t1;
 
 SET SESSION query_cache_type=@qc_type;
+
+--echo #
+--echo # Bug#18383169: QUERIES WITH RANDOM_BYTES() ENTER QUERY CACHE
+--echo #
+
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (1);
+FLUSH STATUS;
+
+--echo # Test that RANDOM_BYTES queries are not cached
+SELECT * FROM t1 WHERE RANDOM_BYTES(16);
+SHOW STATUS LIKE 'Qcache_not_cached';
+
+--echo # same with AES_ENCRYPT
+SELECT * FROM t1 WHERE AES_ENCRYPT('a','a');
+SHOW STATUS LIKE 'Qcache_not_cached';
+
+DROP TABLE t1;
+FLUSH STATUS;

sql/item_create.cc

@@ -250,6 +250,9 @@ class Create_func_aes_base : public Create_native_func
     /* Unsafe for SBR since result depends on a session variable */
     thd->lex->set_stmt_unsafe(LEX::BINLOG_STMT_UNSAFE_SYSTEM_FUNCTION);
 
+    /* Not safe to cache either */
+    thd->lex->set_uncacheable(UNCACHEABLE_SIDEEFFECT);
+
     if (item_list != NULL)
       arg_count= item_list->elements;
 
@@ -337,6 +340,8 @@ class Create_func_random_bytes : public Create_func_arg1
   {
     /* it is unsafe for SBR since it uses crypto random from the ssl library */
     thd->lex->set_stmt_unsafe(LEX::BINLOG_STMT_UNSAFE_SYSTEM_FUNCTION);
+    /* Not safe to cache either */
+    thd->lex->set_uncacheable(UNCACHEABLE_RAND);
     return new (thd->mem_root) Item_func_random_bytes(arg1);
   }
   static Create_func_random_bytes s_singleton;