FAQ
If you'd like an integer, I think that '0' is pretty standard for
"disable quantity cap" in most other places.
- Aaron

Jim Kellerman wrote:
num_versions=all ?

---
Jim Kellerman, Senior Engineer; Powerset
jim@powerset.com


-----Original Message-----
From: Michael Stack
Sent: Wednesday, November 07, 2007 9:59 AM
To: hadoop-user@lucene.apache.org
Cc: stuhood@webmail.us
Subject: Re: HBase num_versions

In the absence of a num_versions qualifier, shell makes
presumption that you want ALL versions. Changing the default
to be 1 would mean that we would have to add some other means
of specifying all versions ("num_versions=-1" or some such
oddity). What ye think?
St.Ack


Jim Kellerman wrote:
Yes, for num_versions > 1, HBase has to dig through the
memcache, and multiple HStore files until it has found the
requested number of versions or runs out of places to look.
This is especially apparent if there is only 1 version. It
has to do a lot of work for nothing.
Please enter a Jira for the HBase shell to default the
number of versions to 1.
---
Jim Kellerman, Senior Engineer; Powerset jim@powerset.com



-----Original Message-----
From: Stu Hood
Sent: Tuesday, November 06, 2007 11:23 PM
To: hadoop-user@lucene.apache.org
Subject: HBase num_versions

Hey guys,

Just noticed some surprising behavior for select statements
in HBase 0.15: a select command without a num_versions = 1
clause takes 2 orders of magnitude longer to run than a
bare select.
Is this inconsistent implementation, or is it taking extra
time to scan for additional versions? If this isn't a bug,
then perhaps the default for num_versions should be 1 to keep
things snappy by default.

============================================================

Hbase> describe test;
+-------------------------------------------------------------
----------------+
Column Family Descriptor
+-------------------------------------------------------------
----------------+
name: hex, max versions: 3, compression: NONE, in memory:
false, max length:|
2147483647, bloom filter: none
+-------------------------------------------------------------
----------------+
1 columnfamily(s) in set (0.310 sec)
Hbase> select hex: from test where row = '3980000'
num_versions = 1;
3cbae0
1 row(s) in set (0.016 sec)
Hbase> select hex: from test where row = '3980000';
3cbae0
1 row(s) in set (1.882 sec)

============================================================


Thanks,


Stu Hood
Webmail.us
"You manage your business. We'll manage your email."(r)


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