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commit a01ad355663b44c427315ecafcee5463d2117c79 Author: Shajini Thayasingh <[email protected]> AuthorDate: Mon Oct 23 10:14:09 2023 -0700 IMPALA-12491: [DOCS] Add a note on the cache item Described how the scan request will access the cache when there is no change in the mtime in the file metadata. Change-Id: I508ce667181d635c17373c7336ea9f83984d7641 Reviewed-on: http://gerrit.cloudera.org:8080/20611 Tested-by: Impala Public Jenkins <[email protected]> Reviewed-by: Quanlong Huang <[email protected]> Reviewed-by: Michael Smith <[email protected]> --- docs/topics/impala_data_cache.xml | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/docs/topics/impala_data_cache.xml b/docs/topics/impala_data_cache.xml index 47e912d89..9c18635e9 100644 --- a/docs/topics/impala_data_cache.xml +++ b/docs/topics/impala_data_cache.xml @@ -92,6 +92,10 @@ under the License. <codeblock>--data_cache_eviction_policy=<varname>policy</varname> </codeblock> </p> + <note>The cache item will not expire as long as the same file metadata is used in the query. + This is because the cache key consists of the filename, mtime (last modified time of the + file), and file offset. If the mtime in the file metadata remains unchanged, the scan request + will consistently access the cache (provided that there is enough capacity).</note> </conbody> </concept>
