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. |