[impala] 02/02: IMPALA-11483: [DOCS] Document EXPIRE SNAPSHOTS functionality

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commit 876829951dc23ac044e79c3ed3088207d812d3bb
Author: Tamas Mate <tm...@cloudera.com>
AuthorDate: Thu Aug 11 16:43:44 2022 +0200

    IMPALA-11483: [DOCS] Document EXPIRE SNAPSHOTS functionality
    
    This commit documents the Iceberg expire snapshot functionality.
    
    Testing:
     - Built the docs locally and verified the generated html.
    
    Change-Id: Iddd927dd1b6ee3b99dd29982018a610389e64836
    Reviewed-on: http://gerrit.cloudera.org:8080/18838
    Reviewed-by: Tamas Mate <tm...@apache.org>
    Tested-by: Tamas Mate <tm...@apache.org>
---
 docs/topics/impala_iceberg.xml | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/docs/topics/impala_iceberg.xml b/docs/topics/impala_iceberg.xml
index 78c865832..1ae133623 100644
--- a/docs/topics/impala_iceberg.xml
+++ b/docs/topics/impala_iceberg.xml
@@ -506,6 +506,38 @@ CREATE TABLE new_ice_tbl LIKE orig_ice_tbl;
     </conbody>
   </concept>
 
+  <concept id="iceberg_expire_snapshots">
+    <title>Expiring snapshots</title>
+    <conbody>
+      <p>
+        Iceberg snapshots accumulate until they are deleted by a user action. Snapshots
+        can be deleted with <codeph>ALTER TABLE ... EXECUTE expire_snapshots(...)</codeph>
+        statement, which will expire snapshots that are older than the specified
+        timestamp. For example:
+        <codeblock>
+ALTER TABLE ice_tbl EXECUTE expire_snapshots('2022-01-04 10:00:00');
+ALTER TABLE ice_tbl EXECUTE expire_snapshots(now() - interval 5 days);
+        </codeblock>
+      </p>
+      <p>
+        Expire snapshots:
+        <ul>
+          <li>does not remove old metadata files by default.</li>
+          <li>does not remove orphaned data files.</li>
+          <li>respects the minimum number of snapshots to keep:
+          <codeph>history.expire.min-snapshots-to-keep</codeph> table property.</li>
+        </ul>
+      </p>
+      <p>
+        Old metadata file clean up can be configured with
+        <codeph>write.metadata.delete-after-commit.enabled=true</codeph> and
+        <codeph>write.metadata.previous-versions-max</codeph> table properties. This
+        allows automatic metadata file removal after operations that modify metadata
+        such as expiring snapshots or inserting data.
+      </p>
+    </conbody>
+  </concept>
+
   <concept id="iceberg_table_properties">
     <title>Iceberg table properties</title>
     <conbody>