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https://issues.apache.org/jira/browse/PHOENIX-1594?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14281507#comment-14281507
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Jeffrey Zhong commented on PHOENIX-1594:
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It seems that's not the case. Here is the scan in
UngroupedAggregateRegionObserver#doPostScannerOpen() call. You can see the
query projects all columns in the first column family and we don't turn off
cacheBlocks either.
{noformat}
scan
{"timeRange":[0,305],"batch":-1,"startRow":"000000000000001","stopRow":"000000000000002",
"loadColumnFamiliesOnDemand":true,"totalColumns":1,"cacheBlocks":true,
"families":{"A":["ALL"]},"maxResultSize":-1,"maxVersions":1,"caching":1000}
{noformat}
In the aggregator, I can see the passed in Tuple has two KVs:
{noformat}
[000000000000002/A:UNIQUE_USER_COUNT/300/Put/vlen=4/mvcc=7,
000000000000002/A:_0/300/Put/vlen=0/mvcc=7]
{noformat}
> Using KeyOnlyFilter for simple query "select count(1) from <table>"
> -------------------------------------------------------------------
>
> Key: PHOENIX-1594
> URL: https://issues.apache.org/jira/browse/PHOENIX-1594
> Project: Phoenix
> Issue Type: Improvement
> Reporter: Jeffrey Zhong
>
> I found that underlying scan for query "select count(1) or count(*) from
> <table>" still project all columns.
> It should be fast if we use KeyOnlyFilter for this simple query.
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