Make iterator-based read code the One True Path
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Key: CASSANDRA-287
URL: https://issues.apache.org/jira/browse/CASSANDRA-287
Project: Cassandra
Issue Type: Bug
Reporter: Jonathan Ellis
Assignee: Jonathan Ellis
Attachments:
0001-CASSANDRA-287-r-m-unused-and-dangerous-RowReadComman.txt,
0002-rename-lock_-sstableLock_.txt,
0003-refactor-out-QueryFilter-SliceQueryFilter.txt,
0004-replace-namesfilter-with-NamesQueryFilter.-mv-filter.txt,
0005-nuke-timefilter.txt,
0006-add-IdentityQueryFilter-finish-removing-IFilter.txt
Since CASSANDRA-172 we've had two read paths; the old, ad-hoc path based on the
faulty assumption that we could skip checking older sstables if we got a hit
earlier in the path (fixed in CASSANDRA-223 but still bearing the marks of its
origin) and the new iterator-based path.
This makes all read operations go through the iterator path, which cleans
things up enormously and sets the stage for CASSANDRA-139.
I introduce a new QueryFilter interface, which has 3 main methods:
/**
* returns an iterator that returns columns from the given memtable
* matching the Filter criteria in sorted order.
*/
public abstract ColumnIterator getMemColumnIterator(Memtable memtable);
/**
* returns an iterator that returns columns from the given SSTable
* matching the Filter criteria in sorted order.
*/
public abstract ColumnIterator getSSTableColumnIterator(SSTableReader
sstable) throws IOException;
/**
* subcolumns of a supercolumn are unindexed, so to pick out parts of those
we operate in-memory.
* @param superColumn
*/
public abstract void filterSuperColumn(SuperColumn superColumn);
The first two are for pulling out indexed top-level columns, from a memtable or
an sstable, respectively.
If the query is on subcolumns of a supercolumn, which are unindexed,
CFS.getColumnFamily does an indexed Name filter on the supercolumn, then asks
filterSuperColumn on the primary QueryFilter to pick out the parts the user is
requesting.
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