~ubuntu-branches/ubuntu/oneiric/postgresql-9.1/oneiric-security : contents of doc/src/sgml/html/catalog-pg-amop.html at revision 14

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><H1
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><A
NAME="CATALOG-PG-AMOP"
>45.4. <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="AEN84865"
></A
><P
><B
>Table 45-4. <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"
>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
>&nbsp;</TD
><TD
>Operator strategy number</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>amoppurpose</TT
></TD
><TD
><TT
CLASS="TYPE"
>char</TT
></TD
><TD
>&nbsp;</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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