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><H1
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><A
NAME="CATALOG-PG-AMOP"
>47.4. <TT
CLASS="STRUCTNAME"
>pg_amop</TT
></A
></H1
><P
> The catalog <TT
CLASS="STRUCTNAME"
>pg_amop</TT
> 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 <I
CLASS="FIRSTTERM"
>search</I
> operator or an
<I
CLASS="FIRSTTERM"
>ordering</I
> 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.)
</P
><DIV
CLASS="TABLE"
><A
NAME="AEN91874"
></A
><P
><B
>Table 47-4. <TT
CLASS="STRUCTNAME"
>pg_amop</TT
> Columns</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Type</TH
><TH
>References</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>oid</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
> </TD
><TD
>Row identifier (hidden attribute; must be explicitly selected)</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amopfamily</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-opfamily.html"
><TT
CLASS="STRUCTNAME"
>pg_opfamily</TT
></A
>.oid</TT
></TD
><TD
>The operator family this entry is for</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amoplefttype</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-type.html"
><TT
CLASS="STRUCTNAME"
>pg_type</TT
></A
>.oid</TT
></TD
><TD
>Left-hand input data type of operator</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amoprighttype</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-type.html"
><TT
CLASS="STRUCTNAME"
>pg_type</TT
></A
>.oid</TT
></TD
><TD
>Right-hand input data type of operator</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amopstrategy</TT
></TD
><TD
><TT
CLASS="TYPE"
>int2</TT
></TD
><TD
> </TD
><TD
>Operator strategy number</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amoppurpose</TT
></TD
><TD
><TT
CLASS="TYPE"
>char</TT
></TD
><TD
> </TD
><TD
>Operator purpose, either <TT
CLASS="LITERAL"
>s</TT
> for search or
<TT
CLASS="LITERAL"
>o</TT
> for ordering</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amopopr</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-operator.html"
><TT
CLASS="STRUCTNAME"
>pg_operator</TT
></A
>.oid</TT
></TD
><TD
>OID of the operator</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amopmethod</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-am.html"
><TT
CLASS="STRUCTNAME"
>pg_am</TT
></A
>.oid</TT
></TD
><TD
>Index access method operator family is for</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amopsortfamily</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-opfamily.html"
><TT
CLASS="STRUCTNAME"
>pg_opfamily</TT
></A
>.oid</TT
></TD
><TD
>The btree operator family this entry sorts according to, if an
ordering operator; zero if a search operator</TD
></TR
></TBODY
></TABLE
></DIV
><P
> A <SPAN
CLASS="QUOTE"
>"search"</SPAN
> operator entry indicates that an index of this operator
family can be searched to find all rows satisfying
<TT
CLASS="LITERAL"
>WHERE</TT
>
<TT
CLASS="REPLACEABLE"
><I
>indexed_column</I
></TT
>
<TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
>
<TT
CLASS="REPLACEABLE"
><I
>constant</I
></TT
>.
Obviously, such an operator must return boolean, and its left-hand input
type must match the index's column data type.
</P
><P
> An <SPAN
CLASS="QUOTE"
>"ordering"</SPAN
> operator entry indicates that an index of this
operator family can be scanned to return rows in the order represented by
<TT
CLASS="LITERAL"
>ORDER BY</TT
>
<TT
CLASS="REPLACEABLE"
><I
>indexed_column</I
></TT
>
<TT
CLASS="REPLACEABLE"
><I
>operator</I
></TT
>
<TT
CLASS="REPLACEABLE"
><I
>constant</I
></TT
>.
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 <TT
CLASS="LITERAL"
>ORDER BY</TT
> are specified by the
<TT
CLASS="STRUCTFIELD"
>amopsortfamily</TT
> column, which must reference
a btree operator family for the operator's result type.
</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
> At present, it's assumed that the sort order for an ordering operator
is the default for the referenced opfamily, i.e., <TT
CLASS="LITERAL"
>ASC NULLS
LAST</TT
>. This might someday be relaxed by adding additional columns
to specify sort options explicitly.
</P
></BLOCKQUOTE
></DIV
><P
> An entry's <TT
CLASS="STRUCTFIELD"
>amopmethod</TT
> must match the
<TT
CLASS="STRUCTNAME"
>opfmethod</TT
> of its containing operator family (including
<TT
CLASS="STRUCTFIELD"
>amopmethod</TT
> here is an intentional denormalization of the
catalog structure for performance reasons). Also,
<TT
CLASS="STRUCTFIELD"
>amoplefttype</TT
> and <TT
CLASS="STRUCTFIELD"
>amoprighttype</TT
> must match
the <TT
CLASS="STRUCTFIELD"
>oprleft</TT
> and <TT
CLASS="STRUCTFIELD"
>oprright</TT
> fields of the
referenced <TT
CLASS="STRUCTNAME"
>pg_operator</TT
> entry.
</P
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