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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: mysterious 'column1' in cql describe
Date Fri, 30 Aug 2013 09:02:18 GMT
The short story is that you're probably not up to date on how CQL and
thrift table definition relate to one another, and that may not be exactly
how you think it does. If you haven't done so, I'd suggest the reading of
http://www.datastax.com/dev/blog/does-cql-support-dynamic-columns-wide-rows(should
answer your "what about dynamic column name" case) and
http://www.datastax.com/dev/blog/thrift-to-cql3 (should help explain how
CQL3 interprets thrift table, and why your saw what you saw).

--
Sylvain


On Fri, Aug 30, 2013 at 9:50 AM, Alexander Shutyaev <shutyaev@gmail.com>wrote:

> 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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