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From Alexander Shutyaev <shuty...@gmail.com>
Subject mysterious 'column1' in cql describe
Date Fri, 30 Aug 2013 07:50:40 GMT
Hi all!

We have encountered the following problem. We create our column families
via hector like this:

ColumnFamilyDefinition cfdef = HFactory.createColumnFamilyDefinition(*
"mykeyspace"*, *"mycf"*);
cfdef.setColumnType(ColumnType.*STANDARD*);
cfdef.setComparatorType(ComparatorType.*UTF8TYPE*);
cfdef.setDefaultValidationClass(*"BytesType"*);
cfdef.setKeyValidationClass(*"UTF8Type"*);
cfdef.setReadRepairChance(0.1);
cfdef.setGcGraceSeconds(864000);
cfdef.setMinCompactionThreshold(4);
cfdef.setMaxCompactionThreshold(32);
cfdef.setReplicateOnWrite(*true*);
cfdef.setCompactionStrategy(*"SizeTieredCompactionStrategy"*);
Map<String, String> compressionOptions = *new* HashMap<String, String>();
compressionOptions.put(*"sstable_compression"*, *""*);
cfdef.setCompressionOptions(compressionOptions);
cluster.addColumnFamily(cfdef, *true*);

When we *describe *this column family via *cqlsh* we get this

CREATE TABLE "mycf" (
  key text,
  column1 text,
  value blob,
  PRIMARY KEY (key, column1)
) WITH COMPACT STORAGE AND
  bloom_filter_fp_chance=0.010000 AND
  caching='KEYS_ONLY' AND
  comment='' AND
  dclocal_read_repair_chance=0.000000 AND
  gc_grace_seconds=864000 AND
  read_repair_chance=0.100000 AND
  replicate_on_write='true' AND
  populate_io_cache_on_flush='false' AND
  compaction={'class': 'SizeTieredCompactionStrategy'} AND
  compression={};

As you can see there is a mysterious *column1* and moreover it is added to
the primary key. We've thought it wrong so we've tried getting rid of it.
We've managed to do it by adding explicit column definitions like this:

BasicColumnDefinition cdef = new BasicColumnDefinition();
cdef.setName(StringSerializer.get().toByteBuffer(*"mycolumn"*));
cdef.setValidationClass(ComparatorType.*BYTESTYPE*.getTypeName());
cdef.setIndexType(ColumnIndexType.*CUSTOM*);
cfdef.addColumnDefinition(cDef);

After this the primary key was like

PRIMARY KEY (key)

The effect of this was *overwhelming* - we got a tremendous performance
improvement and according to stats, the key cache began working while
previously its hit ratio was close to zero.

My questions are

1) What is this all about? Is what we did right?
2) In this project we can provide explicit column definitions. But in
another project we have some column families where this is not possible
because column names are dynamic (based on timestamps). If what we did is
right - how can we adapt this solution to the dynamic column name case?

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