Step 4 - Indexing
Example
After the table has been analyzed and partitioned and the environment
file has been modified to reflect the partitions, the indexes must be
installed and built.
Indexing rules are the same as for indexing any other table. However,
the indexes will be installed on each individual partition, NOT the union
view. This will increase the number of index files created.
The index installation will usually be identical for every partition,
although this is not a requirement.
The partition qualifier should always be installed with Omnidex indexes:
MDK, ASK or composite. This will further enhance performance gains realized
from partitioning the data.
Partitioned MDK Indexes
Partitioned MDK indexes use composite indexes to combine the partition
qualifier with other criteria. This is one of the easiest ways to increase
the speed of large searches and dramatically reduce the cost of large
preintersect counts.
The partition qualifier should be the first component of the composite
index. The composite index components must be non-parsed fields; that
is, installed without the ;KW (keyword) index option.
Using partitioned MDK indexes allows multiple columns to be used as the
partition qualifier. Multiple composite indexes can be used and optimized
in the same query.
 Composite
keys are limited to 240 bytes.
If
a composite key consists of more than 5 components, performance will usually
start to degrade, unless criteria is an exact match with the composite
key.
Partitioned ASK Indexes
Partitioned ASK indexes use the partition qualifier as the first component
of an aggregation index and are extremely useful when the partition qualifier
is provided as criteria in the select statement. Only the portion of the
aggregation index that corresponds to the partition qualifier will be
read, greatly enhancing the query speed.
This is most useful when a large number of aggregations use the same
column (partition qualifier) in the criteria. The criteria applied to
the partition qualifier must use = or an IN clause.
Partitioned ASK indexes are automatic, meaning they require no special
setup, including partitioning of the data. Installing an aggregation index
with the partition qualifier as the first component, partitions the indexes,
whether or not the table itself is partitioned.
The
criteria list in an IN clause is limited to 32 values.
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