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rename operation evaluated

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git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@115 014f5005-505e-4b48-8d0a-63407b615a7c
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LtWorf 2009-03-19 12:56:15 +00:00
parent 720d888c22
commit 79058f3871
1 changed files with 22 additions and 2 deletions
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complexity
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@ -16,6 +16,10 @@ Notation
Single letters will be used to indicate relations and letters between
| will indicate the cardinality (number of tuples) of the relation.
Then after evaluating the big O notation, an attempt to find more
precise results will be done, since it will be important to know
with a certain precision the weight of the operation.
1. UNARY OPERATORS
Relational defines three unary operations, and they will be studied
@ -42,7 +46,23 @@ Notation
In the end we have O(|n|) as complexity for a selection on the
relation n.
The assumption made of considering constant the number of fields is
a bit strong. For example a relation could have hundreds of fields
and two tuples.
So in general, the complexity is something more like O(|n| * f) where
f is the number of the fields.
1.2 Rename
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The rename operation itself is very simple, just modify the list
containing the name of the fields.
The big issue is to copy the content of the relation into a new
relation object, so the new one can be modified.
So the operation depends on the size of the relation: O(|n| * f).
1.3 Projection
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