Allow the types of parameters to PREPARE to be inferred. If a parameter's

data type is unspecified or is declared to be "unknown", the type will
be inferred from the context in which the parameter is used. This was
already possible for protocol-level prepared statements.

1 files changed, 25 insertions, 17 deletions

diff --git a/doc/src/sgml/ref/prepare.sgml b/doc/src/sgml/ref/prepare.sgml
index 51c3985117..738b6320a4 100644
--- a/doc/src/sgml/ref/prepare.sgml
+++ b/doc/src/sgml/ref/prepare.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/prepare.sgml,v 1.17 2006/01/08 07:00:25 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/prepare.sgml,v 1.18 2006/01/15 22:18:46 neilc Exp $
 PostgreSQL documentation
 -->
 
@@ -25,7 +25,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable class="PARAMETER">datatype</replaceable> [, ...] ) ] AS <replaceable class="PARAMETER">statement</replaceable>
+PREPARE <replaceable class="PARAMETER">name</replaceable> [ (<replaceable class="PARAMETER">datatype</replaceable> [, ...] ) ] AS <replaceable class="PARAMETER">statement</replaceable>
 </synopsis>
  </refsynopsisdiv>
 
@@ -45,13 +45,15 @@ PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable c
 
   <para>
    Prepared statements can take parameters: values that are
-   substituted into the statement when it is executed. To include
-   parameters in a prepared statement, supply a list of data types in
-   the <command>PREPARE</command> statement, and, in the statement to
-   be prepared itself, refer to the parameters by position using
-   <literal>$1</literal>, <literal>$2</literal>, etc. When executing
-   the statement, specify the actual values for these parameters in
-   the <command>EXECUTE</command> statement.  Refer to <xref
+   substituted into the statement when it is executed. When creating
+   the prepared statement, refer to parameters by position, using
+   <literal>$1</>, <literal>$2</>, etc. A corresponding list of
+   parameter data types can optionally be specified. When a
+   parameter's data type is not specified or is declared as
+   <literal>unknown</literal>, the type is inferred from the context
+   in which the parameter is used (if possible). When executing the
+   statement, specify the actual values for these parameters in the
+   <command>EXECUTE</command> statement.  Refer to <xref
    linkend="sql-execute" endterm="sql-execute-title"> for more
    information about that.
   </para>
@@ -84,7 +86,7 @@ PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable c
 
   <variablelist>
    <varlistentry>
-    <term><replaceable class="PARAMETER">plan_name</replaceable></term>
+    <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
       An arbitrary name given to this particular prepared
@@ -99,8 +101,11 @@ PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable c
     <term><replaceable class="PARAMETER">datatype</replaceable></term>
     <listitem>
      <para>
-      The data type of a parameter to the prepared statement.  To
-      refer to the parameters in the prepared statement itself, use
+      The data type of a parameter to the prepared statement.  If the
+      data type of a particular parameter is unspecified or is
+      specified as <literal>unknown</literal>, it will be inferred
+      from the context in which the parameter is used. To refer to the
+      parameters in the prepared statement itself, use
       <literal>$1</literal>, <literal>$2</literal>, etc.
      </para>
     </listitem>
@@ -155,8 +160,8 @@ PREPARE <replaceable class="PARAMETER">plan_name</replaceable> [ (<replaceable c
  <refsect1 id="sql-prepare-examples">
   <title id="sql-prepare-examples-title">Examples</title>
   <para>
-   Create a prepared query for an <command>INSERT</command> statement,
-   and then execute it:
+   Create a prepared statement for an <command>INSERT</command>
+   statement, and then execute it:
 <programlisting>
 PREPARE fooplan (int, text, bool, numeric) AS
     INSERT INTO foo VALUES($1, $2, $3, $4);
@@ -165,14 +170,17 @@ EXECUTE fooplan(1, 'Hunter Valley', 't', 200.00);
   </para>
 
   <para>
-   Create a prepared query for a <command>SELECT</command> statement,
-   and then execute it:
+   Create a prepared statement for a <command>SELECT</command>
+   statement, and then execute it:
 <programlisting>
-PREPARE usrrptplan (int, date) AS
+PREPARE usrrptplan (int) AS
     SELECT * FROM users u, logs l WHERE u.usrid=$1 AND u.usrid=l.usrid
     AND l.date = $2;
 EXECUTE usrrptplan(1, current_date);
 </programlisting>
+
+   Note that the data type of the second parameter is not specified,
+   so it is inferred from the context in which <literal>$2</> is used.
   </para>
  </refsect1>
  <refsect1>