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7/29/2019 Fragmentation in OBIEE
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Fragmentation in OBIEE
We use fragmentation when we have fact or dimensional data in oneor more different tables or data is splitted in different data sources.
Then each logical table source represents one data segment.
For example, clients, in the first table are clients from A to M, in the
second from M to Z.
Fragmentation of dimension
If our dimensional data is located on two or more physical tables in
database (tables) or it is on separeted data sources then we canhandle this by using UNION ALL views in physical layer.
However for testing this option we'll simulate this by using CHANNELStable. So we splitt it to a table CHANNELS_OTHER and CHANNELS.
Fragmentation attrubur is CHANNEL_ID.
In our SALES fact table that we used here we use CHANNEL_ID fromboth tables CHANNELS and CHANNELS_OTHER.
Physical model, join:
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SALES.CHANNEL_ID >- CHANNELS.CHANNEL_IDSALES.CHANNEL_ID >- CHANNELS_OTHER.CHANNEL_ID
BMM:
Settings:
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Test in Answers:
Result:
NQQuery.log:
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We see that UNION ALL is generated.
If we choose:
NQQuery.log:
We see that the SQL is using only the second fragmented logical tablesource and the condition is applied only for that logical table source.
If we choose:
NQQuery.log:
If we now choose any other attribut (CHANNEL_CLASS) that is not
CHANELL_ID which we used as a fragmentation key:
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Then this condition is applied on both logical table sources CHANNEL
and CHANNEL_OTHER:
Fragmentation of fact table
Let's split data for SALES 1998 in separate table SALES_HIST. Data
from 1998 we leave in SALES.
Physical model, join:
SALES.TIME_ID >- TIMES.TIME_ID
SALES_HIST.TIME_ID >- TIMES.TIME_ID
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BMM:
Settings (for a fragmentation key we choose CALENDAR_YEAR):
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Test in Answers:
Result:
NQQuery.log:
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If we choose:
NQQuerylog:
If we choose:
NQQuery.log:
If we now choose any other attribut (CALENDAR_MONTH_DESC) that
is not CALENDAR_YEAR which we used as a fragmentation key:
Then this condition is applied on both logical table sources SALES and
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SALES_HIST: