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Improve formatting of PQexecParams argument descriptions, per

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Theo Kramer.
This commit is contained in:
Tom Lane 2006-11-10 22:15:26 +00:00
parent 2c2faa17f2
commit 1456c5b507
1 changed files with 103 additions and 28 deletions
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131
doc/src/sgml/libpq.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.219 2006/10/23 18:10:31 petere Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.220 2006/11/10 22:15:26 tgl Exp $ -->
<chapter id="libpq">
<title><application>libpq</application> - C Library</title>
@ -956,7 +956,7 @@ Applications may use this to determine the version of the database server they
are connected to. The number is formed by converting the major, minor, and
revision numbers into two-decimal-digit numbers and appending them
together. For example, version 8.1.5 will be returned as 80105, and version
8.1 will be returned as 80100 (leading zeroes are not shown). Zero is
8.2 will be returned as 80200 (leading zeroes are not shown). Zero is
returned if the connection is bad.
</para>
</listitem>
@ -1138,41 +1138,116 @@ connections; it will fail when using protocol 2.0.
</para>
<para>
If parameters are used, they are referred to in the command string
as <literal>$1</>, <literal>$2</>, etc.
<parameter>nParams</> is the number of parameters supplied; it is the length
of the arrays <parameter>paramTypes[]</>, <parameter>paramValues[]</>,
<parameter>paramLengths[]</>, and <parameter>paramFormats[]</>. (The
array pointers may be <symbol>NULL</symbol> when <parameter>nParams</> is zero.)
<parameter>paramTypes[]</> specifies, by OID, the data types to be assigned to
the parameter symbols. If <parameter>paramTypes</> is <symbol>NULL</symbol>, or any particular
element in the array is zero, the server assigns a data type to the parameter
symbol in the same way it would do for an untyped literal string.
<parameter>paramValues[]</> specifies the actual values of the parameters.
A null pointer in this array means the corresponding parameter is null;
otherwise the pointer points to a zero-terminated text string (for text
format) or binary data in the format expected by the server (for binary
format).
<parameter>paramLengths[]</> specifies the actual data lengths of
binary-format parameters. It is ignored for null parameters and text-format
parameters. The array pointer may be null when there are no binary
parameters.
<parameter>paramFormats[]</> specifies whether parameters are text (put a zero
in the array) or binary (put a one in the array). If the array pointer is
null then all parameters are presumed to be text.
<parameter>resultFormat</> is zero to obtain results in text format, or one to
obtain results in binary format. (There is not currently a provision to
obtain different result columns in different formats, although that is
possible in the underlying protocol.)
The function arguments are:
<variablelist>
<varlistentry>
<term><parameter>conn</parameter></term>
<listitem>
<para>
The connection object to send the command through.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>command</parameter></term>
<listitem>
<para>
The SQL command string to be executed. If parameters are used, they are
referred to in the command string as <literal>$1</>, <literal>$2</>,
etc.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>nParams</parameter></term>
<listitem>
<para>
The number of parameters supplied; it is the length of the arrays
<parameter>paramTypes[]</>, <parameter>paramValues[]</>,
<parameter>paramLengths[]</>, and <parameter>paramFormats[]</>. (The
array pointers may be <symbol>NULL</symbol> when <parameter>nParams</>
is zero.)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>paramTypes[]</parameter></term>
<listitem>
<para>
Specifies, by OID, the data types to be assigned to the parameter
symbols. If <parameter>paramTypes</> is <symbol>NULL</symbol>, or any
particular element in the array is zero, the server infers a data type
for the parameter symbol in the same way it would do for an untyped
literal string.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>paramValues[]</parameter></term>
<listitem>
<para>
Specifies the actual values of the parameters.
A null pointer in this array means the corresponding parameter is null;
otherwise the pointer points to a zero-terminated text string (for text
format) or binary data in the format expected by the server (for binary
format).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>paramLengths[]</parameter></term>
<listitem>
<para>
Specifies the actual data lengths of binary-format parameters.
It is ignored for null parameters and text-format parameters.
The array pointer may be null when there are no binary parameters.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>paramFormats[]</parameter></term>
<listitem>
<para>
Specifies whether parameters are text (put a zero in the array entry for
the corresponding parameter) or binary (put a one in the array entry for
the corresponding parameter). If the array pointer is null then all
parameters are presumed to be text strings.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>resultFormat</parameter></term>
<listitem>
<para>
Specify zero to obtain results in text format, or one to obtain results
in binary format. (There is not currently a provision to obtain
different result columns in different formats, although that is
possible in the underlying protocol.)
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
The primary advantage of <function>PQexecParams</> over <function>PQexec</>
is that parameter values may be separated from the command string, thus
avoiding the need for tedious and error-prone quoting and escaping.
</para>
<para>
Unlike <function>PQexec</>, <function>PQexecParams</> allows at most one SQL
command in the given string. (There can be semicolons in it, but not more
than one nonempty command.) This is a limitation of the underlying protocol,