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https://issues.apache.org/jira/browse/HIVE-10631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14647156#comment-14647156
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Aaron Tokhy commented on HIVE-10631:
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hive.stats.reliable requires that both numFiles and totalSize be set properly,
regardless of the condition. So if 'create table' or 'create external table'
were to use a location already populated with partitions, it will traverse
those partitions regardless.
As of writing, hive.stats.reliable appears to be set to false by default.
Perhaps stats calculation on creation of partitioned tables can be forgone when
hive.stats.reliable is false only, as stats will be populated on MSCK REPAIR
PARTITIONS or by adding partitions using ALTER TABLE ADD PARTITION.
> create_table_core method has invalid update for Fast Stats
> ----------------------------------------------------------
>
> Key: HIVE-10631
> URL: https://issues.apache.org/jira/browse/HIVE-10631
> Project: Hive
> Issue Type: Bug
> Components: Metastore
> Affects Versions: 0.13.0, 1.0.0
> Reporter: Dongwook Kwon
> Priority: Minor
>
> HiveMetaStore.create_table_core method calls
> MetaStoreUtils.updateUnpartitionedTableStatsFast when hive.stats.autogather
> is on, however for partitioned table, this updateUnpartitionedTableStatsFast
> call scanning warehouse dir and doesn't seem to use it.
> "Fast Stats" was implemented by HIVE-3959
> https://github.com/apache/hive/blob/branch-1.0/metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java#L1363
> From create_table_core method
> {code}
> if (HiveConf.getBoolVar(hiveConf,
> HiveConf.ConfVars.HIVESTATSAUTOGATHER) &&
> !MetaStoreUtils.isView(tbl)) {
> if (tbl.getPartitionKeysSize() == 0) { // Unpartitioned table
> MetaStoreUtils.updateUnpartitionedTableStatsFast(db, tbl, wh,
> madeDir);
> } else { // Partitioned table with no partitions.
> MetaStoreUtils.updateUnpartitionedTableStatsFast(db, tbl, wh,
> true);
> }
> }
> {code}
> Particularly Line 1363: // Partitioned table with no partitions.
> {code}
> MetaStoreUtils.updateUnpartitionedTableStatsFast(db, tbl, wh, true);
> {code}
> This call ends up calling Warehouse.getFileStatusesForUnpartitionedTable and
> do nothing in MetaStoreUtils.updateUnpartitionedTableStatsFast method due to
> newDir flag is always true
> Impact of this bug is minor with HDFS warehouse
> location(hive.metastore.warehouse.dir), it could be big with S3 warehouse
> location especially for large existing partitions.
> Also the impact is heighten with HIVE-6727 when warehouse location is S3,
> basically it could scan wrong S3 directory recursively and do nothing with
> it. I will add more detail of cases in comments
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