Tim Armstrong has posted comments on this change. ( http://gerrit.cloudera.org:8080/8418 )
Change subject: IMPALA-4539: [DOCS] Add known issue for uncompressed Parquet correctness ...................................................................... Patch Set 1: (2 comments) http://gerrit.cloudera.org:8080/#/c/8418/1/docs/topics/impala_known_issues.xml File docs/topics/impala_known_issues.xml: http://gerrit.cloudera.org:8080/#/c/8418/1/docs/topics/impala_known_issues.xml@936 PS1, Line 936: Examine the <codeph>HDFS_SCAN_NODE</codeph> portion of a query profile that scans the This unfortunately won't give accurate info for all queries: if the query isn't materialising any columns (e.g. count(*)) or the file is filtered out by runtime filters, the file compression was inaccurate in previous versions - see IMPALA-5311 and IMPALA-4863 and respectively. One way to tell for sure is to run something like "select * from table" and then look. Or, say, "select min(string_col) from table" http://gerrit.cloudera.org:8080/#/c/8418/1/docs/topics/impala_known_issues.xml@937 PS1, Line 937: suspected table. Look for <q>File Formats</q>. A value containing <codeph>PARQUET/NONE</codeph> It might be helpful to note common cases where uncompressed Parquet is/isn't created. Impala generates snappy-compressed Parquet by default unless compression_codec is changed. Most uncompressed parquet we see in the wild is generated by Hive or other non-Impala tools. -- To view, visit http://gerrit.cloudera.org:8080/8418 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: I731eb0e029dc3cc251f4df0c5a8ad281c81595cb Gerrit-Change-Number: 8418 Gerrit-PatchSet: 1 Gerrit-Owner: John Russell <jruss...@cloudera.com> Gerrit-Reviewer: Greg Rahn <gr...@cloudera.com> Gerrit-Reviewer: John Russell <jruss...@cloudera.com> Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com> Gerrit-Comment-Date: Mon, 30 Oct 2017 21:35:39 +0000 Gerrit-HasComments: Yes
