Impala has a hardcoded limit of 1GB in size for StringVal.
If the length of the string exceeds 1GB, Impala will simply
mark the StringVal as NULL (i.e. is_null = true). It's important
that string functions or built-in UDFs check this field before
accessing the pointer or Impala may end up doing null pointer
access, leading to crashes.
Change-Id: I55777487fff15a521818e39b4f93a8a242770ec2
Reviewed-on: http://gerrit.cloudera.org:8080/2786
Reviewed-by: Dan Hecht <dhecht@cloudera.com>
Tested-by: Internal Jenkins
FunctionContext::Allocate(), FunctionContextImpl::AllocateLocal()
and FunctionContext::Reallocate() allocate memory without taking
memory limits into account. The problem is that these functions
invoke FreePool::Allocate() which may call MemPool::Allocate()
that doesn't check against the memory limits. This patch fixes
the problem by making these FunctionContext functions check for
memory limits and set an error in the FunctionContext object if
memory limits are exceeded.
An alternative would be for these functions to call
MemPool::TryAllocate() instead and return NULL if memory limits
are exceeded. However, this may break some existing external
UDAs which don't check for allocation failures, leading to
unexpected crashes of Impala. Therefore, we stick with this
ad hoc approach until the UDF/UDA interfaces are updated in
the future releases.
Callers of these FunctionContext functions are also updated to
handle potential failed allocations instead of operating on
NULL pointers. The query status will be polled at various
locations and terminate the query.
This patch also fixes MemPool to handle the case in which malloc
may return NULL. It propagates the failure to the callers instead
of continuing to run with NULL pointers. In addition, errors during
aggregate functions' initialization are now properly propagated.
Change-Id: Icefda795cd685e5d0d8a518cbadd37f02ea5e733
Reviewed-on: http://gerrit.cloudera.org:8080/1445
Reviewed-by: Michael Ho <kwho@cloudera.com>
Tested-by: Internal Jenkins
