Mostafa Mokhtar has posted comments on this change. Change subject: IMPALA-5583: [DOCS] Document default_join_distribution_mode query option ......................................................................
Patch Set 2: (3 comments) http://gerrit.cloudera.org:8080/#/c/7300/1/docs/topics/impala_default_join_distribution_mode.xml File docs/topics/impala_default_join_distribution_mode.xml: Line 48: Impala uses the <q>broadcast</q> technique that transmits the entire contents > What is the answer if both tables are missing stats? Does Impala make a ded If both tables are missing stats the table listed first in the query will be the probe side while the second table will be broadcasted. Line 61: from each table to each executor node. > I'd prefer to prepare and fine-tune a brief explanation so I could reuse th This is the description for the SHUFFLE join, we should use similar wording [SHUFFLE] - Makes that join operation use the "partitioned" technique, which divides up corresponding rows from both tables using a hashing algorithm, sending subsets of the rows to other nodes for processing. (The keyword SHUFFLE is used to indicate a "partitioned join", because that type of join is not related to "partitioned tables".) Since the alternative "broadcast" join mechanism is the default when table and index statistics are unavailable, you might use this hint for queries where broadcast joins are unsuitable; typically, partitioned joins are more efficient for joins between large tables of similar size. http://gerrit.cloudera.org:8080/#/c/7300/2/docs/topics/impala_default_join_distribution_mode.xml File docs/topics/impala_default_join_distribution_mode.xml: Line 40: This option determines the join strategy that Impala uses when any of the tables Alex's comment around not using "Join strategy" hasn't been addressed. Can you please use "join distribution" instead? -- To view, visit http://gerrit.cloudera.org:8080/7300 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I4ec6213efc46bce0fe07c590841d51c009fb5c84 Gerrit-PatchSet: 2 Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-Owner: John Russell <jruss...@cloudera.com> Gerrit-Reviewer: Alex Behm <alex.b...@cloudera.com> Gerrit-Reviewer: John Russell <jruss...@cloudera.com> Gerrit-Reviewer: Mostafa Mokhtar <mmokh...@cloudera.com> Gerrit-HasComments: Yes
