GitHub user jianqiao opened a pull request:
https://github.com/apache/incubator-quickstep/pull/333
Fix SeparateChainingHashTable::resize()
This PR fixes the problem that Quickstep hangs when resizing
`SeparateChainingHashTable` during the execution of `BuildHashOperator`.
Here is a sequence of queries that reproduce the problem:
```
CREATE TABLE r(x INT, y INT);
CREATE TABLE s(x INT, y INT);
CREATE TABLE t(x INT, y INT);
INSERT INTO r SELECT 1, 1 FROM generate_series(1, 200) AS g(x);
INSERT INTO s SELECT 1, 1 FROM generate_series(1, 200) AS g(x);
INSERT INTO t SELECT 1, 1 FROM generate_series(1, 1000) AS g(x);
\analyze
SELECT COUNT(*) FROM r, s, t WHERE r.x = s.x AND r.y = s.y AND s.x = t.x
AND s.y = t.y;
```
The problem is caused by the [`resize()`
call](https://github.com/apache/incubator-quickstep/blob/master/storage/HashTable.hpp#L1514)
in `HashTable::putValueAccessorCompositeKey()` when `using_prealloc` is true.
In this case, pre-allocation decides to resize the hash table in order to
consume all the tuples from the current value accessor. However, `resize()`
will alway abort if the hash table is not "actually full", causing infinite
loops.
Note that `SimpleScalarSeparateChainingHashTable` does not have the same
problem, as its [`isFull`
method](https://github.com/apache/incubator-quickstep/blob/master/storage/SimpleScalarSeparateChainingHashTable.hpp#L241)
already takes `extra_buckets` into consideration.
Also note that `LinearOpenAddressingHashTable` seems to have avoided the
hanging problem by using a [`retry_num`
check](https://github.com/apache/incubator-quickstep/blob/master/storage/LinearOpenAddressingHashTable.hpp#L1203).
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/jianqiao/incubator-quickstep fix-hash-resize
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-quickstep/pull/333.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #333
commit d1dbb0d9bc2d1f001deee4039157b0be464870f4
Author: Jianqiao Zhu
Date: 2018-02-18T07:16:07Z
Fix the hanging problem of SeparateChainingHashTable::resize()
---
