Baoding-FenShuaJiang
/
Green_GoodERP18_FSJ_Standard


			
							<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>42.13. Porting from Oracle PL/SQL</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="plpgsql-development-tips.html" title="42.12. Tips for Developing in PL/pgSQL" /><link rel="next" href="pltcl.html" title="Chapter 43. PL/Tcl - Tcl Procedural Language" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">42.13. Porting from <span xmlns="http://www.w3.org/1999/xhtml" class="productname">Oracle</span> PL/SQL</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpgsql-development-tips.html" title="42.12. Tips for Developing in PL/pgSQL">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpgsql.html" title="Chapter 42. PL/pgSQL - SQL Procedural Language">Up</a></td><th width="60%" align="center">Chapter 42. <span xmlns="http://www.w3.org/1999/xhtml" class="application">PL/pgSQL</span> - <acronym xmlns="http://www.w3.org/1999/xhtml" class="acronym">SQL</acronym> Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pltcl.html" title="Chapter 43. PL/Tcl - Tcl Procedural Language">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="PLPGSQL-PORTING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">42.13. Porting from <span class="productname">Oracle</span> PL/SQL</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="plpgsql-porting.html#id-1.8.8.15.6">42.13.1. Porting Examples</a></span></dt><dt><span class="sect2"><a href="plpgsql-porting.html#PLPGSQL-PORTING-OTHER">42.13.2. Other Things to Watch For</a></span></dt><dt><span class="sect2"><a href="plpgsql-porting.html#PLPGSQL-PORTING-APPENDIX">42.13.3. Appendix</a></span></dt></dl></div><a id="id-1.8.8.15.2" class="indexterm"></a><a id="id-1.8.8.15.3" class="indexterm"></a><p>
   This section explains differences between
   <span class="productname">PostgreSQL</span>'s <span class="application">PL/pgSQL</span>
   language and Oracle's <span class="application">PL/SQL</span> language,
   to help developers who port applications from
   <span class="trademark">Oracle</span>® to <span class="productname">PostgreSQL</span>.
  </p><p>
   <span class="application">PL/pgSQL</span> is similar to PL/SQL in many
   aspects. It is a block-structured, imperative language, and all
   variables have to be declared.  Assignments, loops, and conditionals
   are similar.  The main differences you should keep in mind when
   porting from <span class="application">PL/SQL</span> to
   <span class="application">PL/pgSQL</span> are:

    </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
       If a name used in a SQL command could be either a column name of a
       table or a reference to a variable of the function,
       <span class="application">PL/SQL</span> treats it as a column name.  This corresponds
       to <span class="application">PL/pgSQL</span>'s
       <code class="literal">plpgsql.variable_conflict</code> = <code class="literal">use_column</code>
       behavior, which is not the default,
       as explained in <a class="xref" href="plpgsql-implementation.html#PLPGSQL-VAR-SUBST" title="42.11.1. Variable Substitution">Section 42.11.1</a>.
       It's often best to avoid such ambiguities in the first place,
       but if you have to port a large amount of code that depends on
       this behavior, setting <code class="literal">variable_conflict</code> may be the
       best solution.
      </p></li><li class="listitem"><p>
       In <span class="productname">PostgreSQL</span> the function body must be written as
       a string literal.  Therefore you need to use dollar quoting or escape
       single quotes in the function body. (See <a class="xref" href="plpgsql-development-tips.html#PLPGSQL-QUOTE-TIPS" title="42.12.1. Handling of Quotation Marks">Section 42.12.1</a>.)
      </p></li><li class="listitem"><p>
       Data type names often need translation.  For example, in Oracle string
       values are commonly declared as being of type <code class="type">varchar2</code>, which
       is a non-SQL-standard type.  In <span class="productname">PostgreSQL</span>,
       use type <code class="type">varchar</code> or <code class="type">text</code> instead.  Similarly, replace
       type <code class="type">number</code> with <code class="type">numeric</code>, or use some other numeric
       data type if there's a more appropriate one.
      </p></li><li class="listitem"><p>
       Instead of packages, use schemas to organize your functions
       into groups.
      </p></li><li class="listitem"><p>
       Since there are no packages, there are no package-level variables
       either. This is somewhat annoying.  You can keep per-session state
       in temporary tables instead.
      </p></li><li class="listitem"><p>
       Integer <code class="command">FOR</code> loops with <code class="literal">REVERSE</code> work
       differently: <span class="application">PL/SQL</span> counts down from the second
       number to the first, while <span class="application">PL/pgSQL</span> counts down
       from the first number to the second, requiring the loop bounds
       to be swapped when porting.  This incompatibility is unfortunate
       but is unlikely to be changed. (See <a class="xref" href="plpgsql-control-structures.html#PLPGSQL-INTEGER-FOR" title="42.6.5.5. FOR (Integer Variant)">Section 42.6.5.5</a>.)
      </p></li><li class="listitem"><p>
       <code class="command">FOR</code> loops over queries (other than cursors) also work
       differently: the target variable(s) must have been declared,
       whereas <span class="application">PL/SQL</span> always declares them implicitly.
       An advantage of this is that the variable values are still accessible
       after the loop exits.
      </p></li><li class="listitem"><p>
       There are various notational differences for the use of cursor
       variables.
      </p></li></ul></div><p>
   </p><div class="sect2" id="id-1.8.8.15.6"><div class="titlepage"><div><div><h3 class="title">42.13.1. Porting Examples</h3></div></div></div><p>
    <a class="xref" href="plpgsql-porting.html#PGSQL-PORTING-EX1" title="Example 42.9. Porting a Simple Function from PL/SQL to PL/pgSQL">Example 42.9</a> shows how to port a simple
    function from <span class="application">PL/SQL</span> to <span class="application">PL/pgSQL</span>.
   </p><div class="example" id="PGSQL-PORTING-EX1"><p class="title"><strong>Example 42.9. Porting a Simple Function from <span class="application">PL/SQL</span> to <span class="application">PL/pgSQL</span></strong></p><div class="example-contents"><p>
     Here is an <span class="productname">Oracle</span> <span class="application">PL/SQL</span> function:
</p><pre class="programlisting">
CREATE OR REPLACE FUNCTION cs_fmt_browser_version(v_name varchar2,
                                                  v_version varchar2)
RETURN varchar2 IS
BEGIN
    IF v_version IS NULL THEN
        RETURN v_name;
    END IF;
    RETURN v_name || '/' || v_version;
END;
/
show errors;
</pre><p>
    </p><p>
     Let's go through this function and see the differences compared to
     <span class="application">PL/pgSQL</span>:

     </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
        The type name <code class="type">varchar2</code> has to be changed to <code class="type">varchar</code>
        or <code class="type">text</code>.  In the examples in this section, we'll
        use <code class="type">varchar</code>, but <code class="type">text</code> is often a better choice if
        you do not need specific string length limits.
       </p></li><li class="listitem"><p>
        The <code class="literal">RETURN</code> key word in the function
        prototype (not the function body) becomes
        <code class="literal">RETURNS</code> in
        <span class="productname">PostgreSQL</span>.
        Also, <code class="literal">IS</code> becomes <code class="literal">AS</code>, and you need to
        add a <code class="literal">LANGUAGE</code> clause because <span class="application">PL/pgSQL</span>
        is not the only possible function language.
       </p></li><li class="listitem"><p>
        In <span class="productname">PostgreSQL</span>, the function body is considered
        to be a string literal, so you need to use quote marks or dollar
        quotes around it.  This substitutes for the terminating <code class="literal">/</code>
        in the Oracle approach.
       </p></li><li class="listitem"><p>
        The <code class="literal">show errors</code> command does not exist in
        <span class="productname">PostgreSQL</span>, and is not needed since errors are
        reported automatically.
       </p></li></ul></div><p>
    </p><p>
     This is how this function would look when ported to
     <span class="productname">PostgreSQL</span>:

</p><pre class="programlisting">
CREATE OR REPLACE FUNCTION cs_fmt_browser_version(v_name varchar,
                                                  v_version varchar)
RETURNS varchar AS $$
BEGIN
    IF v_version IS NULL THEN
        RETURN v_name;
    END IF;
    RETURN v_name || '/' || v_version;
END;
$$ LANGUAGE plpgsql;
</pre><p>
    </p></div></div><br class="example-break" /><p>
    <a class="xref" href="plpgsql-porting.html#PLPGSQL-PORTING-EX2" title="Example 42.10. Porting a Function that Creates Another Function from PL/SQL to PL/pgSQL">Example 42.10</a> shows how to port a
    function that creates another function and how to handle the
    ensuing quoting problems.
   </p><div class="example" id="PLPGSQL-PORTING-EX2"><p class="title"><strong>Example 42.10. Porting a Function that Creates Another Function from <span class="application">PL/SQL</span> to <span class="application">PL/pgSQL</span></strong></p><div class="example-contents"><p>
     The following procedure grabs rows from a
     <code class="command">SELECT</code> statement and builds a large function
     with the results in <code class="literal">IF</code> statements, for the
     sake of efficiency.
    </p><p>
     This is the Oracle version:
</p><pre class="programlisting">
CREATE OR REPLACE PROCEDURE cs_update_referrer_type_proc IS
    CURSOR referrer_keys IS
        SELECT * FROM cs_referrer_keys
        ORDER BY try_order;
    func_cmd VARCHAR(4000);
BEGIN
    func_cmd := 'CREATE OR REPLACE FUNCTION cs_find_referrer_type(v_host IN VARCHAR2,
                 v_domain IN VARCHAR2, v_url IN VARCHAR2) RETURN VARCHAR2 IS BEGIN';

    FOR referrer_key IN referrer_keys LOOP
        func_cmd := func_cmd ||
          ' IF v_' || referrer_key.kind
          || ' LIKE ''' || referrer_key.key_string
          || ''' THEN RETURN ''' || referrer_key.referrer_type
          || '''; END IF;';
    END LOOP;

    func_cmd := func_cmd || ' RETURN NULL; END;';

    EXECUTE IMMEDIATE func_cmd;
END;
/
show errors;
</pre><p>
    </p><p>
     Here is how this function would end up in <span class="productname">PostgreSQL</span>:
</p><pre class="programlisting">
CREATE OR REPLACE PROCEDURE cs_update_referrer_type_proc() AS $func$
DECLARE
    referrer_keys CURSOR IS
        SELECT * FROM cs_referrer_keys
        ORDER BY try_order;
    func_body text;
    func_cmd text;
BEGIN
    func_body := 'BEGIN';

    FOR referrer_key IN referrer_keys LOOP
        func_body := func_body ||
          ' IF v_' || referrer_key.kind
          || ' LIKE ' || quote_literal(referrer_key.key_string)
          || ' THEN RETURN ' || quote_literal(referrer_key.referrer_type)
          || '; END IF;' ;
    END LOOP;

    func_body := func_body || ' RETURN NULL; END;';

    func_cmd :=
      'CREATE OR REPLACE FUNCTION cs_find_referrer_type(v_host varchar,
                                                        v_domain varchar,
                                                        v_url varchar)
        RETURNS varchar AS '
      || quote_literal(func_body)
      || ' LANGUAGE plpgsql;' ;

    EXECUTE func_cmd;
END;
$func$ LANGUAGE plpgsql;
</pre><p>
     Notice how the body of the function is built separately and passed
     through <code class="literal">quote_literal</code> to double any quote marks in it.  This
     technique is needed because we cannot safely use dollar quoting for
     defining the new function: we do not know for sure what strings will
     be interpolated from the <code class="structfield">referrer_key.key_string</code> field.
     (We are assuming here that <code class="structfield">referrer_key.kind</code> can be
     trusted to always be <code class="literal">host</code>, <code class="literal">domain</code>, or
     <code class="literal">url</code>, but <code class="structfield">referrer_key.key_string</code> might be
     anything, in particular it might contain dollar signs.) This function
     is actually an improvement on the Oracle original, because it will
     not generate broken code when <code class="structfield">referrer_key.key_string</code> or
     <code class="structfield">referrer_key.referrer_type</code> contain quote marks.
    </p></div></div><br class="example-break" /><p>
    <a class="xref" href="plpgsql-porting.html#PLPGSQL-PORTING-EX3" title="Example 42.11. Porting a Procedure With String Manipulation and OUT Parameters from PL/SQL to PL/pgSQL">Example 42.11</a> shows how to port a function
    with <code class="literal">OUT</code> parameters and string manipulation.
    <span class="productname">PostgreSQL</span> does not have a built-in
    <code class="function">instr</code> function, but you can create one
    using a combination of other
    functions. In <a class="xref" href="plpgsql-porting.html#PLPGSQL-PORTING-APPENDIX" title="42.13.3. Appendix">Section 42.13.3</a> there is a
    <span class="application">PL/pgSQL</span> implementation of
    <code class="function">instr</code> that you can use to make your porting
    easier.
   </p><div class="example" id="PLPGSQL-PORTING-EX3"><p class="title"><strong>Example 42.11. Porting a Procedure With String Manipulation and
    <code class="literal">OUT</code> Parameters from <span class="application">PL/SQL</span> to
    <span class="application">PL/pgSQL</span></strong></p><div class="example-contents"><p>
     The following <span class="productname">Oracle</span> PL/SQL procedure is used
     to parse a URL and return several elements (host, path, and query).
    </p><p>
     This is the Oracle version:
</p><pre class="programlisting">
CREATE OR REPLACE PROCEDURE cs_parse_url(
    v_url IN VARCHAR2,
    v_host OUT VARCHAR2,  -- This will be passed back
    v_path OUT VARCHAR2,  -- This one too
    v_query OUT VARCHAR2) -- And this one
IS
    a_pos1 INTEGER;
    a_pos2 INTEGER;
BEGIN
    v_host := NULL;
    v_path := NULL;
    v_query := NULL;
    a_pos1 := instr(v_url, '//');

    IF a_pos1 = 0 THEN
        RETURN;
    END IF;
    a_pos2 := instr(v_url, '/', a_pos1 + 2);
    IF a_pos2 = 0 THEN
        v_host := substr(v_url, a_pos1 + 2);
        v_path := '/';
        RETURN;
    END IF;

    v_host := substr(v_url, a_pos1 + 2, a_pos2 - a_pos1 - 2);
    a_pos1 := instr(v_url, '?', a_pos2 + 1);

    IF a_pos1 = 0 THEN
        v_path := substr(v_url, a_pos2);
        RETURN;
    END IF;

    v_path := substr(v_url, a_pos2, a_pos1 - a_pos2);
    v_query := substr(v_url, a_pos1 + 1);
END;
/
show errors;
</pre><p>
    </p><p>
     Here is a possible translation into <span class="application">PL/pgSQL</span>:
</p><pre class="programlisting">
CREATE OR REPLACE FUNCTION cs_parse_url(
    v_url IN VARCHAR,
    v_host OUT VARCHAR,  -- This will be passed back
    v_path OUT VARCHAR,  -- This one too
    v_query OUT VARCHAR) -- And this one
AS $$
DECLARE
    a_pos1 INTEGER;
    a_pos2 INTEGER;
BEGIN
    v_host := NULL;
    v_path := NULL;
    v_query := NULL;
    a_pos1 := instr(v_url, '//');

    IF a_pos1 = 0 THEN
        RETURN;
    END IF;
    a_pos2 := instr(v_url, '/', a_pos1 + 2);
    IF a_pos2 = 0 THEN
        v_host := substr(v_url, a_pos1 + 2);
        v_path := '/';
        RETURN;
    END IF;

    v_host := substr(v_url, a_pos1 + 2, a_pos2 - a_pos1 - 2);
    a_pos1 := instr(v_url, '?', a_pos2 + 1);

    IF a_pos1 = 0 THEN
        v_path := substr(v_url, a_pos2);
        RETURN;
    END IF;

    v_path := substr(v_url, a_pos2, a_pos1 - a_pos2);
    v_query := substr(v_url, a_pos1 + 1);
END;
$$ LANGUAGE plpgsql;
</pre><p>

     This function could be used like this:
</p><pre class="programlisting">
SELECT * FROM cs_parse_url('http://foobar.com/query.cgi?baz');
</pre><p>
    </p></div></div><br class="example-break" /><p>
    <a class="xref" href="plpgsql-porting.html#PLPGSQL-PORTING-EX4" title="Example 42.12. Porting a Procedure from PL/SQL to PL/pgSQL">Example 42.12</a> shows how to port a procedure
    that uses numerous features that are specific to Oracle.
   </p><div class="example" id="PLPGSQL-PORTING-EX4"><p class="title"><strong>Example 42.12. Porting a Procedure from <span class="application">PL/SQL</span> to <span class="application">PL/pgSQL</span></strong></p><div class="example-contents"><p>
     The Oracle version:

</p><pre class="programlisting">
CREATE OR REPLACE PROCEDURE cs_create_job(v_job_id IN INTEGER) IS
    a_running_job_count INTEGER;
BEGIN
    LOCK TABLE cs_jobs IN EXCLUSIVE MODE;

    SELECT count(*) INTO a_running_job_count FROM cs_jobs WHERE end_stamp IS NULL;

    IF a_running_job_count &gt; 0 THEN
        COMMIT; -- free lock
        raise_application_error(-20000,
                 'Unable to create a new job: a job is currently running.');
    END IF;

    DELETE FROM cs_active_job;
    INSERT INTO cs_active_job(job_id) VALUES (v_job_id);

    BEGIN
        INSERT INTO cs_jobs (job_id, start_stamp) VALUES (v_job_id, now());
    EXCEPTION
        WHEN dup_val_on_index THEN NULL; -- don't worry if it already exists
    END;
    COMMIT;
END;
/
show errors
</pre><p>
   </p><p>
    This is how we could port this procedure to <span class="application">PL/pgSQL</span>:

</p><pre class="programlisting">
CREATE OR REPLACE PROCEDURE cs_create_job(v_job_id integer) AS $$
DECLARE
    a_running_job_count integer;
BEGIN
    LOCK TABLE cs_jobs IN EXCLUSIVE MODE;

    SELECT count(*) INTO a_running_job_count FROM cs_jobs WHERE end_stamp IS NULL;

    IF a_running_job_count &gt; 0 THEN
        COMMIT; -- free lock
        RAISE EXCEPTION 'Unable to create a new job: a job is currently running'; -- <span id="co.plpgsql-porting-raise"></span>(1)
    END IF;

    DELETE FROM cs_active_job;
    INSERT INTO cs_active_job(job_id) VALUES (v_job_id);

    BEGIN
        INSERT INTO cs_jobs (job_id, start_stamp) VALUES (v_job_id, now());
    EXCEPTION
        WHEN unique_violation THEN -- <span id="co.plpgsql-porting-exception"></span>(2)
            -- don't worry if it already exists
    END;
    COMMIT;
END;
$$ LANGUAGE plpgsql;
</pre><p>

    </p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#co.plpgsql-porting-raise">(1)</a> </p></td><td valign="top" align="left"><p>
       The syntax of <code class="literal">RAISE</code> is considerably different from
       Oracle's statement, although the basic case <code class="literal">RAISE</code>
       <em class="replaceable"><code>exception_name</code></em> works
       similarly.
      </p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#co.plpgsql-porting-exception">(2)</a> </p></td><td valign="top" align="left"><p>
       The exception names supported by <span class="application">PL/pgSQL</span> are
       different from Oracle's.  The set of built-in exception names
       is much larger (see <a class="xref" href="errcodes-appendix.html" title="Appendix A. PostgreSQL Error Codes">Appendix A</a>).  There
       is not currently a way to declare user-defined exception names,
       although you can throw user-chosen SQLSTATE values instead.
      </p></td></tr></table></div><p>
   </p></div></div><br class="example-break" /></div><div class="sect2" id="PLPGSQL-PORTING-OTHER"><div class="titlepage"><div><div><h3 class="title">42.13.2. Other Things to Watch For</h3></div></div></div><p>
    This section explains a few other things to watch for when porting
    Oracle <span class="application">PL/SQL</span> functions to
    <span class="productname">PostgreSQL</span>.
   </p><div class="sect3" id="PLPGSQL-PORTING-EXCEPTIONS"><div class="titlepage"><div><div><h4 class="title">42.13.2.1. Implicit Rollback after Exceptions</h4></div></div></div><p>
     In <span class="application">PL/pgSQL</span>, when an exception is caught by an
     <code class="literal">EXCEPTION</code> clause, all database changes since the block's
     <code class="literal">BEGIN</code> are automatically rolled back.  That is, the behavior
     is equivalent to what you'd get in Oracle with:

</p><pre class="programlisting">
BEGIN
    SAVEPOINT s1;
    ... code here ...
EXCEPTION
    WHEN ... THEN
        ROLLBACK TO s1;
        ... code here ...
    WHEN ... THEN
        ROLLBACK TO s1;
        ... code here ...
END;
</pre><p>

     If you are translating an Oracle procedure that uses
     <code class="command">SAVEPOINT</code> and <code class="command">ROLLBACK TO</code> in this style,
     your task is easy: just omit the <code class="command">SAVEPOINT</code> and
     <code class="command">ROLLBACK TO</code>.  If you have a procedure that uses
     <code class="command">SAVEPOINT</code> and <code class="command">ROLLBACK TO</code> in a different way
     then some actual thought will be required.
    </p></div><div class="sect3" id="id-1.8.8.15.7.4"><div class="titlepage"><div><div><h4 class="title">42.13.2.2. <code class="command">EXECUTE</code></h4></div></div></div><p>
     The <span class="application">PL/pgSQL</span> version of
     <code class="command">EXECUTE</code> works similarly to the
     <span class="application">PL/SQL</span> version, but you have to remember to use
     <code class="function">quote_literal</code> and
     <code class="function">quote_ident</code> as described in <a class="xref" href="plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN" title="42.5.4. Executing Dynamic Commands">Section 42.5.4</a>.  Constructs of the
     type <code class="literal">EXECUTE 'SELECT * FROM $1';</code> will not work
     reliably unless you use these functions.
    </p></div><div class="sect3" id="PLPGSQL-PORTING-OPTIMIZATION"><div class="titlepage"><div><div><h4 class="title">42.13.2.3. Optimizing <span class="application">PL/pgSQL</span> Functions</h4></div></div></div><p>
     <span class="productname">PostgreSQL</span> gives you two function creation
     modifiers to optimize execution: <span class="quote">“<span class="quote">volatility</span>”</span> (whether
     the function always returns the same result when given the same
     arguments) and <span class="quote">“<span class="quote">strictness</span>”</span> (whether the function
     returns null if any argument is null).  Consult the <a class="xref" href="sql-createfunction.html" title="CREATE FUNCTION"><span class="refentrytitle">CREATE FUNCTION</span></a>
     reference page for details.
    </p><p>
     When making use of these optimization attributes, your
     <code class="command">CREATE FUNCTION</code> statement might look something
     like this:

</p><pre class="programlisting">
CREATE FUNCTION foo(...) RETURNS integer AS $$
...
$$ LANGUAGE plpgsql STRICT IMMUTABLE;
</pre><p>
    </p></div></div><div class="sect2" id="PLPGSQL-PORTING-APPENDIX"><div class="titlepage"><div><div><h3 class="title">42.13.3. Appendix</h3></div></div></div><p>
    This section contains the code for a set of Oracle-compatible
    <code class="function">instr</code> functions that you can use to simplify
    your porting efforts.
   </p><a id="id-1.8.8.15.8.3" class="indexterm"></a><pre class="programlisting">
--
-- instr functions that mimic Oracle's counterpart
-- Syntax: instr(string1, string2 [, n [, m]])
-- where [] denotes optional parameters.
--
-- Search string1, beginning at the nth character, for the mth occurrence
-- of string2.  If n is negative, search backwards, starting at the abs(n)'th
-- character from the end of string1.
-- If n is not passed, assume 1 (search starts at first character).
-- If m is not passed, assume 1 (find first occurrence).
-- Returns starting index of string2 in string1, or 0 if string2 is not found.
--

CREATE FUNCTION instr(varchar, varchar) RETURNS integer AS $$
BEGIN
    RETURN instr($1, $2, 1);
END;
$$ LANGUAGE plpgsql STRICT IMMUTABLE;


CREATE FUNCTION instr(string varchar, string_to_search_for varchar,
                      beg_index integer)
RETURNS integer AS $$
DECLARE
    pos integer NOT NULL DEFAULT 0;
    temp_str varchar;
    beg integer;
    length integer;
    ss_length integer;
BEGIN
    IF beg_index &gt; 0 THEN
        temp_str := substring(string FROM beg_index);
        pos := position(string_to_search_for IN temp_str);

        IF pos = 0 THEN
            RETURN 0;
        ELSE
            RETURN pos + beg_index - 1;
        END IF;
    ELSIF beg_index &lt; 0 THEN
        ss_length := char_length(string_to_search_for);
        length := char_length(string);
        beg := length + 1 + beg_index;

        WHILE beg &gt; 0 LOOP
            temp_str := substring(string FROM beg FOR ss_length);
            IF string_to_search_for = temp_str THEN
                RETURN beg;
            END IF;

            beg := beg - 1;
        END LOOP;

        RETURN 0;
    ELSE
        RETURN 0;
    END IF;
END;
$$ LANGUAGE plpgsql STRICT IMMUTABLE;


CREATE FUNCTION instr(string varchar, string_to_search_for varchar,
                      beg_index integer, occur_index integer)
RETURNS integer AS $$
DECLARE
    pos integer NOT NULL DEFAULT 0;
    occur_number integer NOT NULL DEFAULT 0;
    temp_str varchar;
    beg integer;
    i integer;
    length integer;
    ss_length integer;
BEGIN
    IF occur_index &lt;= 0 THEN
        RAISE 'argument ''%'' is out of range', occur_index
          USING ERRCODE = '22003';
    END IF;

    IF beg_index &gt; 0 THEN
        beg := beg_index - 1;
        FOR i IN 1..occur_index LOOP
            temp_str := substring(string FROM beg + 1);
            pos := position(string_to_search_for IN temp_str);
            IF pos = 0 THEN
                RETURN 0;
            END IF;
            beg := beg + pos;
        END LOOP;

        RETURN beg;
    ELSIF beg_index &lt; 0 THEN
        ss_length := char_length(string_to_search_for);
        length := char_length(string);
        beg := length + 1 + beg_index;

        WHILE beg &gt; 0 LOOP
            temp_str := substring(string FROM beg FOR ss_length);
            IF string_to_search_for = temp_str THEN
                occur_number := occur_number + 1;
                IF occur_number = occur_index THEN
                    RETURN beg;
                END IF;
            END IF;

            beg := beg - 1;
        END LOOP;

        RETURN 0;
    ELSE
        RETURN 0;
    END IF;
END;
$$ LANGUAGE plpgsql STRICT IMMUTABLE;

</pre></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plpgsql-development-tips.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpgsql.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pltcl.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">42.12. Tips for Developing in <span class="application">PL/pgSQL</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 43. PL/Tcl - Tcl Procedural Language</td></tr></table></div></body></html>