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IMPALA-13071: Update the doc of Impala components

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Change-Id: I83192110d29c4d44529d1276a17c9da4a91435aa
Reviewed-on: http://gerrit.cloudera.org:8080/21621
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Reviewed-by: Quanlong Huang <huangquanlong@gmail.com>
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m-sanjana19
2024-07-29 20:49:29 +05:30
committed by Quanlong Huang
parent 72e38f0e75
commit b1941c8f17
1 changed files with 18 additions and 13 deletions
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docs/topics/impala_components.xml
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@@ -141,20 +141,25 @@ under the License.
<conbody>
<p> The Impala component known as the Catalog Service relays the metadata
changes from Impala SQL statements to all the Impala daemons in a
cluster. It is physically represented by a daemon process named
<codeph>catalogd</codeph>. You only need such a process on one host in
a cluster. Because the requests are passed through the StateStore
daemon, it makes sense to run the <cmdname>statestored</cmdname> and
<cmdname>catalogd</cmdname> services on the same host. </p>
<p> The Impala component known as the Catalog Service relays the metadata changes from Impala
SQL statements to all the Impala coordinators in a cluster. It is physically represented by
a daemon process named <codeph>catalogd</codeph>. You only need such a process on one host
in a cluster. Because the requests are passed through the StateStore daemon, it makes sense
to run the <cmdname>statestored</cmdname> and <cmdname>catalogd</cmdname> services on the
same host. </p>
<p> The catalog service avoids the need to issue <codeph>REFRESH</codeph>
and <codeph>INVALIDATE METADATA</codeph> statements when the metadata
changes are performed by statements issued through Impala. When you
create a table, load data, and so on through Hive, you do need to issue
<codeph>REFRESH</codeph> or <codeph>INVALIDATE METADATA</codeph> on an
Impala daemon before executing a query there. </p>
<p> The catalog service avoids the need to issue <codeph>REFRESH</codeph> and
<codeph>INVALIDATE METADATA</codeph> statements when the metadata changes are performed by
statements issued through Impala.
</p>
<p> When you create a table, load data, and so on through Hive, you do need to issue
<codeph>REFRESH</codeph> or <codeph>INVALIDATE METADATA</codeph> on an Impala daemon
before executing a query. Performing <codeph>REFRESH</codeph> or <codeph>INVALIDATE
METADATA</codeph> is not required when <cite>Automatic Invalidation/Refresh of
Metadata</cite> is enabled. See <xref href="impala_metadata.xml#impala_metadata">Automatic
Invalidation/Refresh of Metadata</xref> also known as the Hive Metastore (HMS) event
processor.<note id="note_eyx_qcp_fcc" type="note">From Impala 4.1, Automatic
Invalidation/Refresh of Metadata is enabled by default.</note></p>
<p>
This feature touches a number of aspects of Impala: