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https://issues.apache.org/jira/browse/HBASE-20866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16539743#comment-16539743
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Vikas Vishwakarma commented on HBASE-20866:
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[~reidchan] [~yuzhih...@gmail.com] [~apurtell] [~vrodionov] that is right.
There will still be good amount of diff between 0.98 and 1.3. For us primarily
using HBase through phoenix and more SQL like use cases with large number of
columns we tend to see amplified impact of such differences. For direct HBase
use cases (non-phoenix) and relatively smaller schema (fewer CQs) we don't see
a major regression between 0.98 and 1.3. In the attached patch I have
attempted to completely get rid of the array to arraylist conversion both for
normal as well as partial result handling to avoid having to deal with arrays
and arraylist separately in loadcache. So I have replaced the
getResultsToAddToCache(..) with loadResultsToCache(..) that processes the
result array and directly adds it to the cache within the same function,
without using/returning an intermediate arraylist both for normal results as
well as partial results.
Please review, I will fix the checkstyle warnings and get some benchmark test
runs with this change since this also includes the changes for partial results
handling which was not done earlier.
> HBase 1.x scan performance degradation compared to 0.98 version
> ---------------------------------------------------------------
>
> Key: HBASE-20866
> URL: https://issues.apache.org/jira/browse/HBASE-20866
> Project: HBase
> Issue Type: Bug
> Affects Versions: 1.3.2
> Reporter: Vikas Vishwakarma
> Assignee: Vikas Vishwakarma
> Priority: Critical
> Fix For: 1.5.0, 1.2.7, 1.3.3, 1.4.6
>
> Attachments: HBASE-20866.branch-1.3.001.patch
>
>
> Internally while testing 1.3 as part of migration from 0.98 to 1.3 we
> observed perf degradation in scan performance for phoenix queries varying
> from few 10's to upto 200% depending on the query being executed. We tried
> simple native HBase scan and there also we saw upto 40% degradation in
> performance when the number of column qualifiers are high (40-50+)
> To identify the root cause of performance diff between 0.98 and 1.3 we
> carried out lot of experiments with profiling and git bisect iterations,
> however we were not able to identify any particular source of scan
> performance degradation and it looked like this is an accumulated degradation
> of 5-10% over various enhancements and refactoring.
> We identified few major enhancements like partialResult handling,
> ScannerContext with heartbeat processing, time/size limiting, RPC
> refactoring, etc that could have contributed to small degradation in
> performance which put together could be leading to large overall degradation.
> One of the changes is
> [HBASE-11544|https://jira.apache.org/jira/browse/HBASE-11544] which
> implements partialResult handling. In ClientScanner.java the results received
> from server are cached on the client side by converting the result array into
> an ArrayList. This function gets called in a loop depending on the number of
> rows in the scan result. Example for ten’s of millions of rows scanned, this
> can be called in the order of millions of times.
> In almost all the cases 99% of the time (except for handling partial results,
> etc). We are just taking the resultsFromServer converting it into a ArrayList
> resultsToAddToCache in addResultsToList(..) and then iterating over the list
> again and adding it to cache in loadCache(..) as given in the code path below
> In ClientScanner → loadCache(..) → getResultsToAddToCache(..) →
> addResultsToList(..) →
> {code:java}
> loadCache() {
> ...
> List<Result> resultsToAddToCache =
> getResultsToAddToCache(values, callable.isHeartbeatMessage());
> ...
> …
> for (Result rs : resultsToAddToCache) {
> rs = filterLoadedCell(rs);
> cache.add(rs);
> ...
> }
> }
> getResultsToAddToCache(..) {
> ..
> final boolean isBatchSet = scan != null && scan.getBatch() > 0;
> final boolean allowPartials = scan != null &&
> scan.getAllowPartialResults();
> ..
> if (allowPartials || isBatchSet) {
> addResultsToList(resultsToAddToCache, resultsFromServer, 0,
> (null == resultsFromServer ? 0 : resultsFromServer.length));
> return resultsToAddToCache;
> }
> ...
> }
> private void addResultsToList(List<Result> outputList, Result[] inputArray,
> int start, int end) {
> if (inputArray == null || start < 0 || end > inputArray.length) return;
> for (int i = start; i < end; i++) {
> outputList.add(inputArray[i]);
> }
> }{code}
>
> It looks like we can avoid the result array to arraylist conversion
> (resultsFromServer --> resultsToAddToCache ) for the first case which is also
> the most frequent case and instead directly take the values arraay returned
> by callable and add it to the cache without converting it into ArrayList.
> I have taken both these flags allowPartials and isBatchSet out in loadcahe()
> and I am directly adding values to scanner cache if the above condition is
> pass instead of coverting it into arrayList by calling
> getResultsToAddToCache(). For example:
> {code:java}
> protected void loadCache() throws IOException {
> Result[] values = null;
> ..
> final boolean isBatchSet = scan != null && scan.getBatch() > 0;
> final boolean allowPartials = scan != null && scan.getAllowPartialResults();
> ..
> for (;;) {
> try {
> values = call(callable, caller, scannerTimeout);
> ..
> } catch (DoNotRetryIOException | NeedUnmanagedConnectionException e) {
> ..
> }
> if (allowPartials || isBatchSet) { // DIRECTLY COPY values TO CACHE
> if (values != null) {
> for (int v=0; v<values.length; v++) {
> Result rs = values[v];
> ....
> cache.add(rs);
> ...
> } else { // DO ALL THE REGULAR PARTIAL RESULT HANDLING ..
> List<Result> resultsToAddToCache =
> getResultsToAddToCache(values, callable.isHeartbeatMessage());
> for (Result rs : resultsToAddToCache) {
> ....
> cache.add(rs);
> ...
> }
> }
> {code}
>
> I am seeing upto 10% improvement in scan time with these changes, sample PE
> execution results given below.
> ||PE (1M , 1 thread)||with addResultsToList||without
> addResultsToList||%improvement||
> |ScanTest|9228|8448|9|
> |RandomScanWithRange10Test|393413|378222|4|
> |RandomScanWithRange100Test|1041860|980147|6|
> Similarly we are observing upto 10% improvement in simple native HBase scan
> test used internally that just scans through a large region filtering all the
> rows. I still have to do the phoenix query tests with this change. Posting
> the initial observations for feedback/comments and suggestions.
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