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Subject: RE: general question about datamodel => empty columns
Date: Mon, 19 Jan 2015 09:48:39 +0900
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Hi,

(Warning: I'm kind of a newbie...)=20
I would make the tables as follows:

<table1: Single column (named 'c') to save space by avoiding the =
overhead by the key and multiple cells>
row1: type1 + foo
row2: type2 + bar
row3: type1 + baz
row4: type2 + whatever

<index1: Again single column, and the data value is duplicated from =
table1. With this you can just Scan through the index1 to get the =
values, avoiding Gets to table1.>
type1 + row1: foo
type1 + row3: baz
type2 + row2: bar
type2 + row4: whatever

<index2> Not needed

Cheers.

-----Original Message-----
From: Wilm Schumacher [mailto:wilm.schumacher@gmail.com]=20
Sent: Saturday, January 17, 2015 6:23 AM
To: user@hbase.apache.org
Subject: general question about datamodel =3D> empty columns

Hi,

I run into a problem , which I encounter several times by now and =
perhaps you can help me.

What should I include in tables where just the qualifier is needed? E.g.
in indexing you have to make the reference of the index either by =
columns, or by rows in the index table. But in this way, there is no =
data to put into the table.

An example for clarification:
Suppose you want to make an index for another table which indexes =
something like "type of entry".

<table>
row1 data:type =3D> type1 , data:data =3D> foo
row2 data:type =3D> type2 , data:data =3D> bar
row3 data:type =3D> type1 , data:data =3D> baz
row4 data:type =3D> type2 , data:data =3D> whatever

indexing 1: indexing by columns

<index>
type1 index:row1 =3D> ??? , index:row2 =3D> ???
type2 index:row2 =3D> ??? , index:row4 =3D> ???

indexing 2: indexing by rows
<index>
type1-row1 ??:?? =3D> ??
type1-row3 ??:?? =3D> ??
type2-row2 ??:?? =3D> ??
type2-row3 ??:?? =3D> ??

works if there is any column family file to scan. Thus I need data.

either way ... I actually have to put data where it is'n needed.

What should I do to insert into the columns? By now I mostly use the =
timestamp of creation, which in my opinion is quite stupid, as I have =
the timestamp in the column right away. This only would waste space. I =
could use empty strings (bytes), which will work, but somehow feels =
wrong.

What are you using? Is empty string/useless timestamp common practice?

Best wishes,

Wilm