optimizer suggestion
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Key: CORE-5006
URL: http://tracker.firebirdsql.org/browse/CORE-5006
Project: Firebird Core
Issue Type: Improvement
Components: Engine
Affects Versions: 2.5.2 Update 1
Environment: not critical - but seen in Fedora Linux and Windoze
Reporter: Ray Holme
I feel it would be a serious enhancement for the optimizer to consider heavily
using an index
a) if an only if the index contains ALL the conditions referenced in the
WHERE clause
b) if multiple indices could satisfy ALL conditions referenced in the WHERE
clause
a choice might be made depending on the cardinality of the set - it
might be cheaper
to just use NATURAL anyway rather than making bit-maps
c) while a LIKE or CONTAINING clause with a leading "%" normally kills this
rule
- it should still be considered if the index would satisfy ALL of the
WHERE conditions
d) the value of choosing the index should increase even more if the index is
computed
and the WHERE clause referenced this computed field
- the cost of a NATURAL search increases if the field is computed (my
UDF or even upper)
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