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ASF GitHub Bot commented on DRILL-5207: --------------------------------------- Github user parthchandra commented on a diff in the pull request: https://github.com/apache/drill/pull/723#discussion_r98289161 --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/util/filereader/BufferedDirectBufInputStream.java --- @@ -179,10 +189,10 @@ private int getNextBlock() throws IOException { this.curPosInStream = getInputStream().getPos(); bytesRead = nBytes; logger.trace( --- End diff -- Sure. > Improve Parquet scan pipelining > ------------------------------- > > Key: DRILL-5207 > URL: https://issues.apache.org/jira/browse/DRILL-5207 > Project: Apache Drill > Issue Type: Bug > Components: Storage - Parquet > Affects Versions: 1.9.0 > Reporter: Parth Chandra > Assignee: Parth Chandra > Fix For: 1.10 > > > The parquet reader's async page reader is not quite efficiently pipelined. > The default size of the disk read buffer is 4MB while the page reader reads > ~1MB at a time. The Parquet decode is also processing 1MB at a time. This > means the disk is idle while the data is being processed. Reducing the buffer > to 1MB will reduce the time the processing thread waits for the disk read > thread. > Additionally, since the data to process a page may be more or less than 1MB, > a queue of pages will help so that the disk scan does not block (until the > queue is full), waiting for the processing thread. > Additionally, the BufferedDirectBufInputStream class reads from disk as soon > as it is initialized. Since this is called at setup time, this increases the > setup time for the query and query execution does not begin until this is > completed. > There are a few other inefficiencies - options are read every time a page > reader is created. Reading options can be expensive. -- This message was sent by Atlassian JIRA (v6.3.4#6332)