* Change Null-safe equal operator from cross join to hash join
ISSUE-2136
This commit change the join method from cross join to hash join when the equal operator is Null-safe '<=>'.
It will improve the speed of query which has the Null-safe equal operator.
The finds_nulls field is used to save if there is Null-safe operator.
The finds_nulls[i] is true means that the i-th equal operator is Null-safe.
The equal function in hash table will return true, if both val and loc are NULL when finds_nulls[i] is true.
The new msg of limit exceed: "Memory exceed limit. %msg, Backend:%ip, fragment:%id Used:% , Limit:%. xxx".
This commit unifies the msg of 'Memory exceed limit' such as check_query_state, RETURN_IF_LIMIT_EXCEEDED and LIMIT_EXCEEDED.
* Reduce UT binary size
Almost every module depend on ExecEnv, and ExecEnv contains all
singleton, which make UT binary contains all object files.
This patch seperate ExecEnv's initial and destory to anthor file to
avoid other file's dependence. And status.cc include debug_util.h which
depend tuple.h tuple_row.h, and I move get_stack_trace() to
stack_util.cpp to reduce status.cc's dependence.
I add USE_RTTI=1 to build rocksdb to avoid linking librocksdb.a
Issue: #292
* Update
