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From "Kim Jin Chul (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-3193: Show table's comment on show tables
Date Mon, 08 Jan 2018 03:16:54 GMT
Kim Jin Chul has posted comments on this change. ( http://gerrit.cloudera.org:8080/8851 )

Change subject: IMPALA-3193: Show table's comment on show tables
......................................................................


Patch Set 4:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/8851/4/fe/src/main/java/org/apache/impala/service/JniFrontend.java
File fe/src/main/java/org/apache/impala/service/JniFrontend.java:

http://gerrit.cloudera.org:8080/#/c/8851/4/fe/src/main/java/org/apache/impala/service/JniFrontend.java@304
PS4, Line 304: for (Table table: tables) {
             :         org.apache.hadoop.hive.metastore.api.Table msTable
             :           = table.getMetaStoreTable(msClient);
             :         if (msTable != null) {
             :           String comment = msTable.getParameters().get("comment");
             :           comments.add(comment != null ? comment : "");
             :         }
             :       }
> This is not acceptable from a performance point of view. You're making a ca
Regarding your suggestion, there was no loaded tables when I attached debugger. HMS call should
happen once to read comment.

If I understand correctly,
- Do you mean we need to keep comment in catalog(i.e. Table.comment_) to use the value in
catalog for the next call if HMS call happens once?

By the way, as far as I know that HMS table object should be cached in catalog when HMS call
happens once and there is no HMS call on the second call. I mean we don't worry about redundant
HMS calls. The call for every table happens only once.

Please correct me if I am wrong.



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I44f814af05db6f3c027718ade9f474f8b8153bcd
Gerrit-Change-Number: 8851
Gerrit-PatchSet: 4
Gerrit-Owner: Kim Jin Chul <jinchul@gmail.com>
Gerrit-Reviewer: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Gerrit-Reviewer: Kim Jin Chul <jinchul@gmail.com>
Gerrit-Comment-Date: Mon, 08 Jan 2018 03:16:54 +0000
Gerrit-HasComments: Yes

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