Daniel Wong created PHOENIX-5280:
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Summary: 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
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 organizaitonId then additoin skipscan for the trailing key.
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
proessing 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'. Essentailly 1 step to find the
orgId and then a scan of all the departments for that value.
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