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https://issues.apache.org/jira/browse/PHOENIX-1312?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15057283#comment-15057283
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ramkrishna.s.vasudevan commented on PHOENIX-1312:
-------------------------------------------------
[[email protected]]
I understand where the actual projection happens and that is where I have tried
not to project the default CF. Atleast in the eg given in the desc
{code}
if (projector.isProjectEmptyKeyValue()) {
// If nothing projected into scan and we only have one column
family, just allow everything
// to be projected and use a FirstKeyOnlyFilter to skip from
row to row. This turns out to
// be quite a bit faster.
// Where condition columns also will get added into familyMap
// When where conditions are present, we can not add
FirstKeyOnlyFilter at beginning.
if (familyMap.isEmpty() &&
context.getWhereCoditionColumns().isEmpty()
&& table.getColumnFamilies().size() == 1) {
// Project the one column family. We must project a column
family since it's possible
// that there are other non declared column families that
we need to ignore.
scan.addFamily(table.getColumnFamilies().get(0).getName().getBytes());
} else {
byte[] ecf = SchemaUtil.getEmptyColumnFamily(table);
// Project empty key value unless the column family
containing it has
// been projected in its entirety.
// TODO: Only project empty column family when necessary
if (!familyMap.containsKey(ecf) || familyMap.get(ecf) !=
null) {
scan.addColumn(ecf, QueryConstants.EMPTY_COLUMN_BYTES);
}
}
{code}
The else part is where the default CF was added. Now I have tried to avoid
that. In this part of code we don't get directly get the where expression and
whether requiresFinalEvaluation is true or not.
> Do not always project the empty column family
> ---------------------------------------------
>
> Key: PHOENIX-1312
> URL: https://issues.apache.org/jira/browse/PHOENIX-1312
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: ramkrishna.s.vasudevan
> Fix For: 4.7.0
>
> Attachments: PHOENIX-1312_1.patch, Phoenix-1312.patch
>
>
> Often times, we don't need to, but it seems we always are. See
> MultiCfQueryExecIT.testGuidePostsForMultiCFs() where we run a query like this:
> {code}
> SELECT count(*) FROM multi_cf WHERE e.cpu_utilization IS NOT NULL
> {code}
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