This sounds like a perfect example of using windowing functions. Have you
tried something like the following:
select ACCT_ID, CR_RVKD_STAT_CD, ACCT_SFX_NUM, SCURT_FRD_STAT_CD,
CLSD_REAS_CD from (select *, max(instnc_id) *over ()* as max_inst_id FROM
Stat_hist) where instnc_id=max_inst_id
However, I have seen instances where window functions without partitioning
clauses will cause all partitions to be executed on one task (and spark
usually warns about this condition) and this will be very slow. It might
actually be more performant to use the inner join which, even though it is
scanning through the raw data twice, is more parallelizable.
If you have your data stored in a columnar compressed data format like
parquet or orc, the query on the right side of the join should only have a
single column, so I/O on that column would be significantly less than the
full table; you might even be able to squeeze some more performance out of
it (depending on the size of the table), by caching it beforehand.
Nicholas Szandor Hakobian, Ph.D.
Staff Data Scientist
Rally Health
nicholas.hakob...@rallyhealth.com
On Fri, Dec 29, 2017 at 1:02 PM, Lalwani, Jayesh <
jayesh.lalw...@capitalone.com> wrote:
> I have a table, and I want to find the latest records in the table. The
> table has a column called instnc_id that is incremented everyday. So, I
> want to find the records that have the max instnc_id.
>
>
>
> I am trying to do this using subqueries, but it gives me an error. For
> example, when I try this
>
>
>
> select ACCT_ID, CR_RVKD_STAT_CD, ACCT_SFX_NUM, SCURT_FRD_STAT_CD,
> CLSD_REAS_CD from (select *, max(instnc_id) as max_inst_id FROM Stat_hist)
> where instnc_id=max_inst_id
>
>
>
> the error I get is
>
>
>
> Caused by: org.apache.spark.sql.AnalysisException: cannot resolve
> '`max_inst_id`' given input columns: [CR_RVKD_STAT_CD, ACCT_SFX_NUM,
> CLSD_REAS_CD, ACCT_ID, instnc_id, SCURT_FRD_STAT_CD]; line 1 pos 172;
>
> 'Project ['ACCT_ID, 'CR_RVKD_STAT_CD, 'ACCT_SFX_NUM, 'SCURT_FRD_STAT_CD,
> CLSD_REAS_CD, scalar-subquery#298 [] AS max_inst_id#299]
>
> : +- 'Project [unresolvedalias('max('instnc_id), None)]
>
> : +- 'UnresolvedRelation `Stat_hist`
>
> +- 'Filter (instnc_id#92 = 'max_inst_id)
>
> +- SubqueryAlias stat_hist
>
> +- Project [ACCT_ID#0, ACCT_SFX_NUM#1, CR_RVKD_STAT_CD#23,
> SCURT_FRD_STAT_CD#34, CLSD_REAS_CD#19, instnc_id#92]
>
>
>
> I have tried various combinations but I keep getting into the same
> problem: It doesn’t recognize max_inst_id as a column.
>
>
>
> The only thing that works is if I get max_inst_id in a dataframe and then
> inner join it with the original table
>
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