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https://issues.apache.org/jira/browse/DRILL-5125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15934933#comment-15934933
]
ASF GitHub Bot commented on DRILL-5125:
---------------------------------------
Github user ppadma commented on a diff in the pull request:
https://github.com/apache/drill/pull/704#discussion_r107219761
--- Diff:
exec/java-exec/src/test/java/org/apache/drill/exec/physical/impl/svremover/TestSVRemover.java
---
@@ -34,4 +38,33 @@ public void testSVRWithNoFilter() throws Exception {
int numOutputRecords =
testPhysical(getFile("remover/sv_with_no_filter.json"));
assertEquals(100, numOutputRecords);
}
+
+ /**
+ * Test the generic version of the selection vector remover copier
+ * class. The code uses the traditional generated version by default.
+ * This test sets the option to use the generic version, then runs
+ * a query that exercises that version.
+ * <p>
+ * Note that the tests here exercise only the SV2 version of the
+ * selection remover; no tests exist for the SV4 version.
+ */
+
+ // TODO: Add an SV4 test once the improved mock data generator
+ // is available.
+
+ @Test
+ public void testGenericCopier() throws Exception {
+ // TODO: replace this with new setup once revised test framework
+ // is available.
+ Properties config = new Properties( );
+ config.put(ExecConstants.SYS_STORE_PROVIDER_LOCAL_ENABLE_WRITE,
"false");
+ config.put(ExecConstants.HTTP_ENABLE, "false");
+ config.put(ExecConstants.REMOVER_ENABLE_GENERIC_COPIER, "true");
+ updateTestCluster(1, DrillConfig.create(config));
+
+ int numOutputRecords = testPhysical(getFile("remover/test1.json"));
+ assertEquals(50, numOutputRecords);
+ numOutputRecords =
testPhysical(getFile("remover/sv_with_no_filter.json"));
+ assertEquals(100, numOutputRecords);
+ }
}
--- End diff --
It would be good to have the tests that cover all the vector types. But,
since it is off by default and you are exercising the code through other unit
tests, this is fine.
+1
> Provide option to use generic code for sv remover
> -------------------------------------------------
>
> Key: DRILL-5125
> URL: https://issues.apache.org/jira/browse/DRILL-5125
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.8.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
>
> Consider a non-typical Drill query: one with 6000 rows but 243 fields.
> Consider this query:
> {code}
> select * from (select *, row_number() over(order by somedate) as rn from
> dfs.`/some/path/data.json`) where rn=10
> {code}
> This produces a query with the following structure:
> {code}
> 00-00 Screen
> 00-01 ProjectAllowDup(*=[$0], rn=[$1])
> 00-02 Project(T0¦¦*=[$0], w0$o0=[$2])
> 00-03 SelectionVectorRemover
> 00-04 Filter(condition=[=($2, 10)])
> 00-05 Window(window#0=[window(partition {} order by [1] rows
> between UNBOUNDED PRECEDING and CURRENT ROW aggs [ROW_NUMBER()])])
> 00-06 SelectionVectorRemover
> 00-07 Sort(sort0=[$1], dir0=[ASC])
> 00-08 Project(T0¦¦*=[$0], validitydate=[$1])
> 00-09 Scan(groupscan=...)
> {code}
> Instrumenting, the code to measure compile time, two “long poles” stood out:
> {code}
> Compile Time for org.apache.drill.exec.test.generated.CopierGen3: 500
> Compile Time for org.apache.drill.exec.test.generated.CopierGen8: 1659
> {code}
> Much of the initial run time of 5578 ms is taken up in compiling two classes
> (2159 ms).
> The classes themselves are very simple: create member variables for 486
> vectors (2 x column count), and call a method on each to do the copy. The
> only type-specific work is the member variable and call to the (non-virtual)
> CopyFrom or CopyFromSafe methods. The generated class can easily be replaced
> by a “generic” class and virtual functions in the vector classes to choose
> the correct copy method.
> Clearly, avoiding code gen means avoiding the compile times with a first-run
> savings. Here are the last 8 runs (out of 10), with code cached turned off
> (forcing a compile on each query run), with and without the generic versions:
> * Original (no code cache): 1832 ms / run
> * Generic (no code cache): 1317 ms / run
> This demonstrates the expected outcome: avoiding compilation of generated
> code saves ~500 ms per run (or 28%). (Note: the numbers above were obtained
> on a version of the code that already had various optimizations described in
> other JIRA entries.)
> The reason, for generating code is that one would expect that 243 in-line
> statements (an unwound loop) to be faster than a loop with 243 iterations. In
> addition, the generic version uses an array in place of ~500 variables, and a
> virtual function call rather than in-line, type-specific calls. One would
> expect the unrolled loop to be faster.
> Repeat the exercise, this time with the code cache turned on so that no
> compile cost is payed for either code path (because the test excludes the
> first two runs in which the generated code is compiled.)
> * Original: 1302 ms / run
> * Generic version: 1040 ms / run
> Contrary to expectations, the loop is faster than the in-line statements. In
> this instance, the array/loop/virtual function version is ~260 ms faster
> (20%).
> The test shows that the code can be simplified, a costly costly code-gen and
> compile step can be skipped, and this query will go faster. Plus, since the
> change removes generated classes from the code cache, there is more room for
> the remaining classes, which may improve the hit rate.
> This ticket offers the performance improvement as an option, described in
> comments.
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