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From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200204130143.g3D1h5O14015@candle.pha.pa.us>
Subject: Re: For review: documentation for libpgtcl pg_execute
In-Reply-To: <a6ours$1vp2$2@jupiter.hub.org>
To: ljb <lbayuk@mindspring.com>
Date: Fri, 12 Apr 2002 21:43:05 -0400 (EDT)
Cc: pgsql-docs@postgresql.org
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I will check the SGML build here.

Patch applied.  Thanks.

---------------------------------------------------------------------------


ljb wrote:
> This is a proposed patch to doc/src/sgml/libpgtcl.sgml which documents the
> libpgtcl "pg_execute" command. This was mentioned on pgsql-interfaces on
> Mar 3. I am posting it here in the hope that someone will check to see if
> it makes sense and is correct SGML-wise.  I did run it through jade, but this
> is my first try at this sort of thing.  Corrections would be appreciated.
> Thanks.
> 
> 
> *** libpgtcl.sgml.orig	Sun Jan 20 17:19:56 2002
> --- libpgtcl.sgml	Wed Mar 13 20:10:35 2002
> ***************
> *** 65,70 ****
> --- 65,73 ----
>       <ENTRY>loop over the result of a SELECT statement</ENTRY>
>     </ROW>
>     <ROW>
> +     <ENTRY><function>pg_execute</function></ENTRY>
> +     <ENTRY>send a query and optionally loop over the results</ENTRY>
> +   <ROW>
>       <ENTRY><function>pg_listen</function></ENTRY>
>       <ENTRY>establish a callback for NOTIFY messages</ENTRY>
>     </ROW>
> ***************
> *** 986,991 ****
> --- 989,1190 ----
>   	pg_select $pgconn "SELECT * FROM table" array {
>   		puts [format "%5d %s" $array(control) $array(name)]
>   	}
> + </ProgramListing>
> + </PARA>
> + </REFSECT1>
> + 
> + </REFENTRY>
> + 
> + <!-- ********************************************************** -->
> + 
> + <REFENTRY ID="PGTCL-PGEXECUTE">
> + <REFMETA>
> + <REFENTRYTITLE>pg_execute</REFENTRYTITLE>
> + <REFMISCINFO>PGTCL - Query Processing</REFMISCINFO>
> + </REFMETA>
> + <REFNAMEDIV>
> + <REFNAME>pg_execute
> + </REFNAME>
> + <REFPURPOSE>
> + send a query and optionally loop over the results
> + </REFPURPOSE>
> + <INDEXTERM ID="IX-PGTCL-PGEXECUTE-1"><PRIMARY>pgtcl</PRIMARY><SECONDARY>query</SECONDARY></INDEXTERM>
> + <INDEXTERM ID="IX-PGTCL-PGEXECUTE-2"><PRIMARY>pg_execute</PRIMARY></INDEXTERM>
> + </REFNAMEDIV>
> + <REFSYNOPSISDIV>
> + <REFSYNOPSISDIVINFO>
> + <DATE>2002-03-06</DATE>
> + </REFSYNOPSISDIVINFO>
> + <SYNOPSIS>
> + pg_execute <OPTIONAL>-array <REPLACEABLE CLASS="PARAMETER">arrayVar</REPLACEABLE></OPTIONAL> <OPTIONAL>-oid <REPLACEABLE CLASS="PARAMETER">oidVar</REPLACEABLE></OPTIONAL> <REPLACEABLE CLASS="PARAMETER">dbHandle</REPLACEABLE> <REPLACEABLE CLASS="PARAMETER">queryString</REPLACEABLE> <OPTIONAL><REPLACEABLE CLASS="PARAMETER">queryProcedure</REPLACEABLE></OPTIONAL>
> + </SYNOPSIS>
> + 
> + <REFSECT2 ID="R2-PGTCL-PGEXECUTE-1">
> + <REFSECT2INFO>
> + <DATE>2002-03-06</DATE>
> + </REFSECT2INFO>
> + <TITLE>Inputs
> + </TITLE>
> + <VARIABLELIST>
> + <VARLISTENTRY>
> + <TERM>
> +   <OPTIONAL>-array <REPLACEABLE CLASS="PARAMETER">arrayVar</REPLACEABLE></OPTIONAL>
> + </TERM>
> + <LISTITEM>
> + <PARA>Specifies the name of an array variable where result tuples are stored,
> + indexed by the field names.
> + This is ignored if queryString is not a SELECT statement. For SELECT
> + statements, if this option is not used, result tuples values are stored
> + in individual variables named according to the field names in the result.
> + </PARA>
> + </LISTITEM>
> + </VARLISTENTRY>
> + <VARLISTENTRY>
> + <TERM>
> +   <OPTIONAL>-oid <REPLACEABLE CLASS="PARAMETER">oidVar</REPLACEABLE></OPTIONAL>
> + </TERM>
> + <LISTITEM>
> + <PARA>Specifies the name of a variable into which the OID from an INSERT
> + statement will be stored.
> + </PARA>
> + </LISTITEM>
> + </VARLISTENTRY>
> + <VARLISTENTRY>
> + <TERM>
> +   <REPLACEABLE CLASS="PARAMETER">dbHandle</REPLACEABLE>
> + </TERM>
> + <LISTITEM>
> + <PARA>Specifies a valid database handle.
> + </PARA>
> + </LISTITEM>
> + </VARLISTENTRY>
> + <VARLISTENTRY>
> + <TERM>
> +   <REPLACEABLE CLASS="PARAMETER">queryString</REPLACEABLE>
> + </TERM>
> + <LISTITEM>
> + <PARA>Specifies a valid SQL query.
> + </PARA>
> + </LISTITEM>
> + </VARLISTENTRY>
> + <VARLISTENTRY>
> + <TERM>
> +   <OPTIONAL><REPLACEABLE CLASS="PARAMETER">queryProcedure</REPLACEABLE></OPTIONAL>
> + </TERM>
> + <LISTITEM>
> + <PARA>Optional command to execute for each result tuple of a SELECT statement.
> + </PARA>
> + </LISTITEM>
> + </VARLISTENTRY>
> + </VARIABLELIST>
> + 
> + </REFSECT2>
> + 
> + <REFSECT2 ID="R2-PGTCL-PGEXECUTE-2">
> + <REFSECT2INFO>
> + <DATE>2002-03-06</DATE>
> + </REFSECT2INFO>
> + <TITLE>Outputs
> + </TITLE>
> + <VARIABLELIST>
> + <VARLISTENTRY>
> + <TERM>
> +   <REPLACEABLE CLASS="PARAMETER">ntuples</REPLACEABLE>
> + </TERM>
> + <LISTITEM>
> + <PARA>
> + The number of tuples affected or returned by the query.
> + </PARA>
> + </LISTITEM>
> + </VARLISTENTRY>
> + </VARIABLELIST>
> + </REFSECT2></REFSYNOPSISDIV>
> + 
> + <REFSECT1 ID="R1-PGTCL-PGEXECUTE-1">
> + <REFSECT1INFO>
> + <DATE>2002-03-06</DATE>
> + </REFSECT1INFO>
> + <TITLE>Description
> + </TITLE>
> + <PARA>
> + <FUNCTION>pg_execute</FUNCTION> submits a query to the PostgreSQL backend.
> + </PARA>
> + <PARA>
> + If the query is not a SELECT statement, the query is executed and the
> + number of tuples affected by the query is returned.  If the query is an
> + INSERT and a single tuple is inserted, the OID of the inserted tuple is
> + stored in the oidVar variable if the optional <PARAMETER>-oid</PARAMETER>
> + argument is supplied.
> + </PARA>
> + <PARA>
> + If the query is a SELECT statement, the query is executed. For each tuple
> + in the result, the tuple field values are stored in the
> + <PARAMETER>arrayVar</PARAMETER> variable,
> + if supplied, using the field names as the array indexes, else in variables
> + named by the field names, and then the optional
> + <PARAMETER>queryProcedure</PARAMETER> is executed if supplied.
> + (Omitting the <PARAMETER>queryProcedure</PARAMETER> probably makes sense
> + only if the query will return a single tuple.)
> + The number of tuples selected is returned.
> + </PARA>
> + <PARA>
> + The <PARAMETER>queryProcedure</PARAMETER> can use the Tcl
> + <LITERAL>break</LITERAL>, <LITERAL>continue</LITERAL>, and
> + <LITERAL>return</LITERAL> commands, with the expected behavior.
> + Note that if the <PARAMETER>queryProcedure</PARAMETER> executes
> + <LITERAL>return</LITERAL>, <FUNCTION>pg_execute</FUNCTION> does
> + not return <PARAMETER>ntuples</PARAMETER>.
> + </PARA>
> + <PARA>
> + <FUNCTION>pg_execute</FUNCTION> is a newer function which provides a
> + superset of the features of <FUNCTION>pg_select</FUNCTION>, and can
> + replace <FUNCTION>pg_exec</FUNCTION> in many cases where access to
> + the result handle is not needed.
> + </PARA>
> + <PARA>
> + For backend-handled errors, <FUNCTION>pg_execute</FUNCTION> will
> + throw a Tcl error and return two element list. The first element
> + is an error code such as <LITERAL>PGRES_FATAL_ERROR</LITERAL>, and
> + the second element is the backend error text. For more serious
> + errors, such as failure to communicate with the backend,
> + <FUNCTION>pg_execute</FUNCTION> will throw a Tcl error and return
> + just the error message text.
> + </PARA>
> + 
> + </REFSECT1>
> + 
> + <REFSECT1 ID="R1-PGTCL-PGEXECUTE-2">
> + <TITLE>Usage
> + </TITLE>
> + <PARA>
> + In the following examples, error checking with <LITERAL>catch</LITERAL>
> + has been omitted for clarity.
> + </PARA>
> + <PARA>
> + Insert a row and save the OID in result_oid:
> + <ProgramListing>
> +     pg_execute -oid result_oid $pgconn "insert into mytable values (1)"
> + </ProgramListing>
> + </PARA>
> + <PARA>
> + Print the item and value fields from each row:
> + <ProgramListing>
> +     pg_execute -array d $pgconn "select item, value from mytable" {
> +        puts "Item=$d(item) Value=$d(value)"
> +     }
> + </ProgramListing>
> + </PARA>
> + <PARA>
> + Find the maximum and minimum values and store them in $s(max) and $s(min):
> + <ProgramListing>
> +     pg_execute -array s $pgconn "select max(value) as max,\
> +       min(value) as min from mytable"
> + </ProgramListing>
> + </PARA>
> + <PARA>
> + Find the maximum and minimum values and store them in $max and $min:
> + <ProgramListing>
> +     pg_execute $pgconn "select max(value) as max, min(value) as min from mytable"
>   </ProgramListing>
>   </PARA>
>   </REFSECT1>
> 
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-- 
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