[IMPALA-4138] RowBatch::AcquireState() cannot be used if the initial capacity of a RowBatch is not known

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.7.0
• Fix Version/s: Impala 2.8.0
• Component/s: Backend
• Target Version: Impala 2.8.0
• Assignee: Henry Robinson
• Reporter: Henry Robinson
• Created: 15/Sep/16 19:06
• Updated: 21/Sep/16 04:01
• Resolved: 21/Sep/16 04:01

Description

If you want to acquire the state of a row batch, the usual pattern is something like:

RowBatch dest(src->row_desc(), batch->capacity(), mem_tracker);
dest.AcquireState(src);

AcquireState() checks to see if the allocated space for tuple ptrs is the same in both batches - this is calculated by capacity * num_tuples_per_row * sizeof(Tuple*), and is fixed in the constructor.

But capacity can change after construction, by calling MarkCapacity(). If this happens, dest will allocate too little memory for the tuple ptrs, and AcquireState() will hit a DCHECK.

The solution seems to be recording the maximum capacity in the c'tor, and using that when constructing dest.