pg_amop stores information about operators associated with access method operator families. There is one row for each operator that is a member of an operator family. A family member can be either a search operator or an ordering operator. An operator can appear in more than one family, but cannot appear in more than one search position nor more than one ordering position within a family. (It is allowed, though unlikely, for an operator to be used for both search and ordering purposes.)
The operator family this entry is for
Left-hand input data type of operator
Right-hand input data type of operator
Operator strategy number
Operator purpose, either
OID of the operator
Index access method operator family is for
The B-tree operator family this entry sorts according to, if an ordering operator; zero if a search operator
A “search” operator entry indicates that an index of this operator family can be searched to find all rows satisfying
constant. Obviously, such an operator must return
boolean, and its left-hand input type must match the index's column data type.
An “ordering” operator entry indicates that an index of this operator family can be scanned to return rows in the order represented by
constant. Such an operator could return any sortable data type, though again its left-hand input type must match the index's column data type. The exact semantics of the
ORDER BY are specified by the
amopsortfamily column, which must reference a B-tree operator family for the operator's result type.
At present, it's assumed that the sort order for an ordering operator is the default for the referenced operator family, i.e.,
ASC NULLS LAST. This might someday be relaxed by adding additional columns to specify sort options explicitly.
amopmethod must match the
opfmethod of its containing operator family (including
amopmethod here is an intentional denormalization of the catalog structure for performance reasons). Also,
amoprighttype must match the
oprright fields of the referenced
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