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From "Paul Rogers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-1162) 25 way join ended up with OOM
Date Tue, 18 Jul 2017 04:55:00 GMT

    [ https://issues.apache.org/jira/browse/DRILL-1162?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16091103#comment-16091103
] 

Paul Rogers commented on DRILL-1162:
------------------------------------

My two cents...

Original log from '15 shows a direct memory OOM error: no more memory to allocate a VarChar
vector.

The recent stack trace shows a OOM for heap memory.

The original stack trace showed many hash joins. Each must build a hash table. At present,
hash join assumes unlimited memory (cannot spill.) Was the original query simply exhausting
available memory because of all the in-flight hash tables?

We've seen cases in which we try to build the hash table for every hash join, but we have
parallelized so much that no hash join can grab enough memory to build its own copy.

The original description did not say how much memory was available or the degree of parallelization.
Would be good to know that.

Suggestion: try to determine if this is a "real" OOM (we need more memory than is available)
or an "artificial" OOM (we are doing something silly, or something is holding onto memory
too long, or parallelization is too great.)

While doing so, would be interesting to know if a spill-to-disk mode for hash join could solve
this long term.

> 25 way join ended up with OOM
> -----------------------------
>
>                 Key: DRILL-1162
>                 URL: https://issues.apache.org/jira/browse/DRILL-1162
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Execution - Flow, Query Planning & Optimization
>            Reporter: Rahul Challapalli
>            Assignee: Volodymyr Vysotskyi
>            Priority: Critical
>             Fix For: Future
>
>         Attachments: error.log, oom_error.log
>
>
> git.commit.id.abbrev=e5c2da0
> The below query results in 0 results being returned 
> select count(*) from `lineitem1.parquet` a 
> inner join `part.parquet` j on a.l_partkey = j.p_partkey 
> inner join `orders.parquet` k on a.l_orderkey = k.o_orderkey 
> inner join `supplier.parquet` l on a.l_suppkey = l.s_suppkey 
> inner join `partsupp.parquet` m on j.p_partkey = m.ps_partkey and l.s_suppkey = m.ps_suppkey

> inner join `customer.parquet` n on k.o_custkey = n.c_custkey 
> inner join `lineitem2.parquet` b on a.l_orderkey = b.l_orderkey 
> inner join `lineitem2.parquet` c on a.l_partkey = c.l_partkey 
> inner join `lineitem2.parquet` d on a.l_suppkey = d.l_suppkey 
> inner join `lineitem2.parquet` e on a.l_extendedprice = e.l_extendedprice 
> inner join `lineitem2.parquet` f on a.l_comment = f.l_comment 
> inner join `lineitem2.parquet` g on a.l_shipdate = g.l_shipdate 
> inner join `lineitem2.parquet` h on a.l_commitdate = h.l_commitdate 
> inner join `lineitem2.parquet` i on a.l_receiptdate = i.l_receiptdate 
> inner join `lineitem2.parquet` o on a.l_receiptdate = o.l_receiptdate 
> inner join `lineitem2.parquet` p on a.l_receiptdate = p.l_receiptdate 
> inner join `lineitem2.parquet` q on a.l_receiptdate = q.l_receiptdate 
> inner join `lineitem2.parquet` r on a.l_receiptdate = r.l_receiptdate 
> inner join `lineitem2.parquet` s on a.l_receiptdate = s.l_receiptdate 
> inner join `lineitem2.parquet` t on a.l_receiptdate = t.l_receiptdate 
> inner join `lineitem2.parquet` u on a.l_receiptdate = u.l_receiptdate 
> inner join `lineitem2.parquet` v on a.l_receiptdate = v.l_receiptdate 
> inner join `lineitem2.parquet` w on a.l_receiptdate = w.l_receiptdate 
> inner join `lineitem2.parquet` x on a.l_receiptdate = x.l_receiptdate;
> However when we remove the last 'inner join' and run the query it returns '716372534'.
Since the last inner join is similar to the one's before it, it should match some records
and return the data appropriately.
> The logs indicated that it actually returned 0 results. Attached the log file.



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