Logical and Physical Operators

LOGICAL OPERATOR PHYSICAL OPERATORS DESCRIPTION
R TableScan
(R)
Full table scan of R.
IndexScan
(R,I)
Ordered scan of R on the index I attributes.
SortScan
(R,{Ai})
Sorted scan of R on the attributes {Ai}.
&pib Project
(O,{Ai})
Projection of O records without duplicate elimination.
&delta Distinct
(O)
Duplicate elimination from O records sorted on the attributes {Ai}.
&tau{Ai} Sort
(O,{Ai})
Sort O records on {Ai}.
&sigma Filter
(O,&psi)
Selection of the O records the satisfy the condition &psi.
IndexFilter
(R,I,&psi)
Selection of the R records using the index I defined on the attributes in &psi.
IndexOnlyFilter
(R,I,{Ai},&psi)
Selection of the R records attributes available in the index I and used in &psi, without any access to R. The attributes {Ai} are a subset of those in I.
&gamma GroupBy
(O, {Ai},{fi})
Grouping of O records sorted on the attributes {Ai} using the aggregate functions in {fi}. The operator returns records with attributes {Ai} and the aggregate functions in {fi}, sorted on the attributes {Ai}.
NestedLoop
(Oe, Oi, &psij)
Nested-loop join.
PageNestedLoop
(&Omicrone, &Omicroni, &psij)
Page nested-loop join.
IndexNestedLoop
(Oe, Oi, &psij)
Index nested-loop join. Oi uses an index on the join attributes.
MergeJoin
(Oe, Oi, &psij)
Merge join. The operand Oe and Oi records are sorted on join attributes. The external operand join attribute is a key.
&cup, &minus, &cap Union, Except, Intersect
(Oe, Oi)
Set operators with the operand records sorted and without duplicates.
&cupb UnionAll
(Oe, Oi)
Union without duplicates elimination.

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