The sorter was dropping on the floor the returned Status of the
PrepareRead() calls. PrepareRead() tries to Pin() blocks. In some
queries with large sorts, those Pin() calls could fail with OOM,
but because the sorter was ignoring the returned Status it would
happily put the unpinned block in the vector of blocks and eventually
seg fault, because the buffer_desc_ of that block was NULL.
This patch fixes this problem and adds a test that eventually we may
want to move to the exhaustive build because it takes quite some time.
It also changes the comments of the sorter class to the doxygen style.
Change-Id: Icad48bcfbb97a68f2d51b015a37a7345ebb5e479
Reviewed-on: http://gerrit.cloudera.org:8080/1156
Reviewed-by: Dan Hecht <dhecht@cloudera.com>
Tested-by: Internal Jenkins
This is the first step to fix issues with large memory allocations. In
this patch, the built-in `group_concat` is no longer allowed to allocate
arbitraryly large strings and crash impala, but is limited to the upper
bound of possible allocations in Impala.
This patch does not perform any functional change, but rather avoids
unnecessary crashes. However, it changes the parameter type of
FindChunk() in MemPool to be a signed 64bit integer. This change allows
the mempool to allocate internally memory of more than one 1GB, but the
public interface of Allocate() is not changed, so the general limitation
remains. The reason for this change is as follows:
1) In a UDF FunctionContext::Reallocate() would allocate slightly more
than 512MB from the FreePool.
2) The free pool tries to double this size to alloocate 1GB from the
MemPool.
3) The MemPool doubles the size again and overflows the signed 32bit
integer in the FindChunk() method. This will then only allocate 1GB
instead of the expected 2GB.
What happens is that one of the callers expected a larger allocation
than actually happened, which will in turn lead to memory corruption as
soon as the memory is accessed.
Change-Id: I068835dfa0ac8f7538253d9fa5cfc3fb9d352f6a
Reviewed-on: http://gerrit.cloudera.org:8080/858
Tested-by: Internal Jenkins
Reviewed-by: Dan Hecht <dhecht@cloudera.com>
