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Daniel Wong closed PHOENIX-5280.
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> Provide Improvements to Scan on Composite PK where Leading Edge not fully Specified but
the edge next columns are in most leading keys
> --------------------------------------------------------------------------------------------------------------------------------------
>
> Key: PHOENIX-5280
> URL: https://issues.apache.org/jira/browse/PHOENIX-5280
> Project: Phoenix
> Issue Type: Improvement
> Reporter: Daniel Wong
> Priority: Minor
>
> Provide Improvements to Scan on Composite PK where Leading Edge not fully Specified but
the edge next columns are in most leading keys
> Recently a user has had an issue where they have a composite pk with 2 columns say (organizationId
varchar, departmentId varchar). They want to query all their data with a condition where
department is fully qualified department. Example SELECT * FROM TABLE WHERE departmentId='123'.
They also know that 95% of the organization leading edge contains the qualified trailing edge.
However department = '123' is less than 5% of the total data in the table.
> Based on the explain plan today for this we would run a Round Robin Full Scan with a
filter on departmentId='123'.
> While one possible approach to not run a full table scan is to build an index on department.
Another approach could be to construct a new version of a skipscan like filter to control
this scan. Essentially we could use 1 lookup to find the organizationId then additional
skipscan for the trailing key. This could be triggered with a sql syntax hint or in the
future data driven.
> For a given region assume the data looks like this.
> ||organizationId||departmentId||
> |org1|100|
> |org4|100|
> |org4|101|
> |org4|123|
> |org5|100|
> |org5|123|
> First query the initial row in the region. We get 'org1','100'. From this we can
construct the next rows of ['org1','123' - 'org1','123\x0'). After processing that block
(in our case 0 rows) we would run to the row at or greater than nextKey(current orgnaziationId),'123'.
This would give us org4,101. We would then run to the row of 'org4','123'. Essentially
1 step to find the orgId and then a scan of all the departments for that value.
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