Quanlong Huang has posted comments on this change. ( http://gerrit.cloudera.org:8080/14394 )
Change subject: IMPALA-8920: [DOCS] Documented the query option for disabling HBase row estimation ...................................................................... Patch Set 2: (2 comments) Thanks for the doc! Added some details about when should we use this. http://gerrit.cloudera.org:8080/#/c/14394/2/docs/topics/impala_disable_hbase_row_est.xml File docs/topics/impala_disable_hbase_row_est.xml: http://gerrit.cloudera.org:8080/#/c/14394/2/docs/topics/impala_disable_hbase_row_est.xml@27 PS2, Line 27: DISABLE_HBASE_ROW_EST Sorry that I should mention it in the parent JIRA. This option is renamed to DISABLE_HBASE_NUM_ROWS_ESTIMATE. The commit message in the parent JIRA is stale. http://gerrit.cloudera.org:8080/#/c/14394/2/docs/topics/impala_disable_hbase_row_est.xml@43 PS2, Line 43: HBase tables in row count and row size estimation. I think we can add more details: While generating a plan for an hbase query, the planner samples the underlying hbase tables to estimated their row count and row size. It may impact the planning time since it requires RPC to hbase. If the hbase table stats does not change a lot in short time, disable the sampling by this query option. Planner will fall back to use HMS table stats instead. So remember to update HMS table stats by COMPUTE STATS or manually setting table statistics with ALTER TABLE. See more in impala_perf_stats.html Not a native speaker, please correct my syntax :) -- To view, visit http://gerrit.cloudera.org:8080/14394 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: Id131b66a3457ef6cbc326a0f3ed99de2a3950c3e Gerrit-Change-Number: 14394 Gerrit-PatchSet: 2 Gerrit-Owner: Alex Rodoni <arod...@cloudera.com> Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com> Gerrit-Reviewer: Quanlong Huang <huangquanl...@gmail.com> Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com> Gerrit-Comment-Date: Wed, 09 Oct 2019 02:28:58 +0000 Gerrit-HasComments: Yes
