diff options
Diffstat (limited to 'doc/src/sgml/ref/create_operator.sgml')
| -rw-r--r-- | doc/src/sgml/ref/create_operator.sgml | 27 |
1 files changed, 14 insertions, 13 deletions
diff --git a/doc/src/sgml/ref/create_operator.sgml b/doc/src/sgml/ref/create_operator.sgml index 40c9799772..11debc3d3a 100644 --- a/doc/src/sgml/ref/create_operator.sgml +++ b/doc/src/sgml/ref/create_operator.sgml @@ -1,6 +1,6 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.21 2001/09/13 15:55:24 petere Exp $ -Postgres documentation +$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.22 2001/12/08 03:24:34 thomas Exp $ +PostgreSQL documentation --> <refentry id="SQL-CREATEOPERATOR"> @@ -205,7 +205,7 @@ CREATE </literallayout> For example, <literal>@-</literal> is an allowed operator name, but <literal>*-</literal> is not. - This restriction allows <productname>Postgres</productname> to + This restriction allows <productname>PostgreSQL</productname> to parse SQL-compliant queries without requiring spaces between tokens. </para> </listitem> @@ -218,7 +218,7 @@ CREATE For example, if you have defined a left-unary operator named <literal>@</literal>, you cannot write <literal>X*@Y</literal>; you must write <literal>X* @Y</literal> to ensure that - <productname>Postgres</productname> reads it as two operator names + <productname>PostgreSQL</productname> reads it as two operator names not one. </para> </note> @@ -242,7 +242,7 @@ CREATE </para> <para> The commutator operator should be identified if one exists, - so that <productname>Postgres</productname> can + so that <productname>PostgreSQL</productname> can reverse the order of the operands if it wishes. For example, the operator area-less-than, <<<, would probably have a commutator @@ -280,7 +280,7 @@ MYBOXES.description !== box '((0,0), (1,1))' </para> <para> If a commutator operator name is supplied, - <productname>Postgres</productname> + <productname>PostgreSQL</productname> searches for it in the catalog. If it is found and it does not yet have a commutator itself, then the commutator's entry is updated to have the newly created operator as its @@ -290,17 +290,18 @@ MYBOXES.description !== box '((0,0), (1,1))' operator should be defined without a commutator or negator (as appropriate). When the second operator is defined, name the first as the commutator or negator. The first - will be updated as a side effect. (As of Postgres 6.5, + will be updated as a side effect. (As of + <application>PostgreSQL</application> <literal>6.5</literal>, it also works to just have both operators refer to each other.) </para> <para> The HASHES, SORT1, and SORT2 options are present to support the query optimizer in performing joins. - <productname>Postgres</productname> can always + <productname>PostgreSQL</productname> can always evaluate a join (i.e., processing a clause with two tuple variables separated by an operator that returns a boolean) by iterative substitution [WONG76]. - In addition, <productname>Postgres</productname> + In addition, <productname>PostgreSQL</productname> can use a hash-join algorithm along the lines of [SHAP86]; however, it must know whether this strategy is applicable. The current hash-join algorithm @@ -321,7 +322,7 @@ MYBOXES.description !== box '((0,0), (1,1))' </para> <para> If other join strategies are found to be practical, - <productname>Postgres</productname> + <productname>PostgreSQL</productname> will change the optimizer and run-time system to use them and will require additional specification when an operator is defined. Fortunately, the research community @@ -336,7 +337,7 @@ MYBOXES.description !== box '((0,0), (1,1))' MYBOXES.description <<< box '((0,0), (1,1))' </programlisting> is present in the qualification, - then <productname>Postgres</productname> may have to + then <productname>PostgreSQL</productname> may have to estimate the fraction of the instances in MYBOXES that satisfy the clause. The function <replaceable class="parameter">res_proc</replaceable> @@ -364,7 +365,7 @@ my_procedure_1 (MYBOXES.description, box '((0,0), (1,1))') <programlisting> MYBOXES.description === box '((0,0), (1,1))' </programlisting> - is that <productname>Postgres</productname> + is that <productname>PostgreSQL</productname> attempts to optimize operators and can decide to use an index to restrict the search space when operators are involved. However, there is no attempt to @@ -428,7 +429,7 @@ CREATE OPERATOR === ( <para> <command>CREATE OPERATOR</command> - is a <productname>Postgres</productname> extension. + is a <productname>PostgreSQL</productname> extension. There is no <command>CREATE OPERATOR</command> statement in <acronym>SQL92</acronym>. </para> |