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jirapos...@reviews.apache.org commented on HBASE-4465: ------------------------------------------------------ ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviews.apache.org/r/2180/#review2358 ----------------------------------------------------------- That is a pretty cool idea. I was looking at this w.r.t. to HBASE-4071 and HBASE-4241, and it looks good from that viewpoint. - Lars On 2011-10-05 18:00:03, Mikhail Bautin wrote: bq. bq. ----------------------------------------------------------- bq. This is an automatically generated e-mail. To reply, visit: bq. https://reviews.apache.org/r/2180/ bq. ----------------------------------------------------------- bq. bq. (Updated 2011-10-05 18:00:03) bq. bq. bq. Review request for hbase. bq. bq. bq. Summary bq. ------- bq. bq. Previously, if we had several StoreFiles for a column family in a region, we would seek in each of them and only then merge the results, even though the row/column we are looking for might only be in the most recent (and the smallest) file. Now we prioritize our reads from those files so that we check the most recent file first. This is done by doing a "lazy seek" which pretends that the next value in the StoreFile is (seekRow, seekColumn, lastTimestampInStoreFile), which is earlier in the KV order than anything that might actually occur in the file. So if we don't find the result in earlier files, that fake KV will bubble up to the top of the KV heap and a real seek will be done. This is expected to significantly reduce the amount of disk IO (as of 09/22/2011 we are doing dark launch testing and measurement). bq. bq. This is joint work with Liyin Tang – huge thanks to him for many helpful discussions on this and the idea of putting fake KVs with the highest timestamp of the StoreFile in the scanner priority queue. bq. bq. bq. This addresses bug HBASE-4465. bq. https://issues.apache.org/jira/browse/HBASE-4465 bq. bq. bq. Diffs bq. ----- bq. bq. src/main/java/org/apache/hadoop/hbase/KeyValue.java aa34006 bq. src/main/java/org/apache/hadoop/hbase/regionserver/AbstractKeyValueScanner.java 94ddce7 bq. src/main/java/org/apache/hadoop/hbase/regionserver/ColumnCount.java 1be0280 bq. src/main/java/org/apache/hadoop/hbase/regionserver/KeyValueHeap.java b8d33e8 bq. src/main/java/org/apache/hadoop/hbase/regionserver/KeyValueScanner.java fbcd276 bq. src/main/java/org/apache/hadoop/hbase/regionserver/MemStore.java 035f765 bq. src/main/java/org/apache/hadoop/hbase/regionserver/NonLazyKeyValueScanner.java PRE-CREATION bq. src/main/java/org/apache/hadoop/hbase/regionserver/ScanQueryMatcher.java dad278a bq. src/main/java/org/apache/hadoop/hbase/regionserver/StoreFile.java abb5931 bq. src/main/java/org/apache/hadoop/hbase/regionserver/StoreFileScanner.java 31bfea7 bq. src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java 64a6e3e bq. src/main/java/org/apache/hadoop/hbase/util/CollectionBackedScanner.java 8ad5aab bq. src/test/java/org/apache/hadoop/hbase/regionserver/TestBlocksRead.java b3beabb bq. src/test/java/org/apache/hadoop/hbase/regionserver/TestMemStore.java 9d2b2a7 bq. bq. Diff: https://reviews.apache.org/r/2180/diff bq. bq. bq. Testing bq. ------- bq. bq. All unit tests should be passing now. Will rebase and re-run again just in case. bq. bq. bq. Thanks, bq. bq. Mikhail bq. bq. > Lazy-seek optimization for StoreFile scanners > --------------------------------------------- > > Key: HBASE-4465 > URL: https://issues.apache.org/jira/browse/HBASE-4465 > Project: HBase > Issue Type: Improvement > Reporter: Mikhail Bautin > Assignee: Mikhail Bautin > Labels: optimization, seek > Fix For: 0.89.20100924, 0.94.0 > > > Previously, if we had several StoreFiles for a column family in a region, we > would seek in each of them and only then merge the results, even though the > row/column we are looking for might only be in the most recent (and the > smallest) file. Now we prioritize our reads from those files so that we check > the most recent file first. This is done by doing a "lazy seek" which > pretends that the next value in the StoreFile is (seekRow, seekColumn, > lastTimestampInStoreFile), which is earlier in the KV order than anything > that might actually occur in the file. So if we don't find the result in > earlier files, that fake KV will bubble up to the top of the KV heap and a > real seek will be done. This is expected to significantly reduce the amount > of disk IO (as of 09/22/2011 we are doing dark launch testing and > measurement). > This is joint work with Liyin Tang -- huge thanks to him for many helpful > discussions on this and the idea of putting fake KVs with the highest > timestamp of the StoreFile in the scanner priority queue. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira