[jira] (HIVE-25800) loadDynamicPartitions in Hive.java should not load all partitions of a managed table

["Sourabh Goyal (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-25800 ]


    Sourabh Goyal deleted comment on HIVE-25800:
    --------------------------------------

was (Author: sourabh912):
Just realized that a part of it is already fixed in  https://issues.apache.org/jira/browse/HIVE-25178.

> loadDynamicPartitions in Hive.java should not load all partitions of a managed table 
> -------------------------------------------------------------------------------------
>
>                 Key: HIVE-25800
>                 URL: https://issues.apache.org/jira/browse/HIVE-25800
>             Project: Hive
>          Issue Type: Improvement
>          Components: Hive
>            Reporter: Sourabh Goyal
>            Assignee: Sourabh Goyal
>            Priority: Major
>
> HIVE-20661 added an improvement in loadDynamicPartitions() api in Hive.java to not add partitions one by one in HMS. As part of that improvement, following code was introduced: 
> {code:java}
> // fetch all the partitions matching the part spec using the partition iterable
> // this way the maximum batch size configuration parameter is considered
> PartitionIterable partitionIterable = new PartitionIterable(Hive.get(), tbl, partSpec,
>           conf.getInt(MetastoreConf.ConfVars.BATCH_RETRIEVE_MAX.getVarname(), 300));
> Iterator<Partition> iterator = partitionIterable.iterator();
> // Match valid partition path to partitions
> while (iterator.hasNext()) {
>   Partition partition = iterator.next();
>   partitionDetailsMap.entrySet().stream()
>           .filter(entry -> entry.getValue().fullSpec.equals(partition.getSpec()))
>           .findAny().ifPresent(entry -> {
>             entry.getValue().partition = partition;
>             entry.getValue().hasOldPartition = true;
>           });
> } {code}
> The above code fetches all the existing partitions for a table from HMS and compare that dynamic partitions list to decide old and new partitions to be added to HMS (in batches). The call to fetch all partitions has introduced a performance regression for tables with large number of partitions (of the order of 100K). 
>  
> This is fixed for external tables in https://issues.apache.org/jira/browse/HIVE-25178.  However for ACID tables there is an open Jira(HIVE-25187). Until we have an appropriate fix in HIVE-25187, we can apply the following: 
> Skip fetching all partitions. Instead, in the threadPool which loads each partition individually,  call get_partition() to check if the partition already exists in HMS or not.  
> This will introduce additional getPartition() call for every partition to be loaded dynamically but removes fetching all existing partitions for a table. 
> I believe this is fine since for tables with small number of existing partitions in HMS - getPartitions() won't add too much overhead but for tables with large number of existing partitions, it will certainly avoid getting all partitions from HMS 
> cc - [~lpinter] [~ngangam] 



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