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|
<?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>43.13. 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 Vsnapshot" /><link rel="prev" href="plpgsql-development-tips.html" title="43.12. Tips for Developing in PL/pgSQL" /><link rel="next" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">43.13. Porting from <span class="productname">Oracle</span> PL/SQL</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpgsql-development-tips.html" title="43.12. Tips for Developing in PL/pgSQL">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><th width="60%" align="center">Chapter 43. <span class="application">PL/pgSQL</span> — <acronym class="acronym">SQL</acronym> Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language">Next</a></td></tr></table><hr /></div><div class="sect1" id="PLPGSQL-PORTING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">43.13. Porting from <span class="productname">Oracle</span> PL/SQL <a href="#PLPGSQL-PORTING" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="plpgsql-porting.html#PLPGSQL-PORTING-EXAMPLES">43.13.1. Porting Examples</a></span></dt><dt><span class="sect2"><a href="plpgsql-porting.html#PLPGSQL-PORTING-OTHER">43.13.2. Other Things to Watch For</a></span></dt><dt><span class="sect2"><a href="plpgsql-porting.html#PLPGSQL-PORTING-APPENDIX">43.13.3. 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 an SQL command could be either a column name of a
table used in the command or a reference to a variable of the function,
<span class="application">PL/SQL</span> treats it as a column name.
By default, <span class="application">PL/pgSQL</span> will throw an error
complaining that the name is ambiguous. You can specify
<code class="literal">plpgsql.variable_conflict</code> = <code class="literal">use_column</code>
to change this behavior to match <span class="application">PL/SQL</span>,
as explained in <a class="xref" href="plpgsql-implementation.html#PLPGSQL-VAR-SUBST" title="43.11.1. Variable Substitution">Section 43.11.1</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="43.12.1. Handling of Quotation Marks">Section 43.12.1</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="43.6.5.5. FOR (Integer Variant)">Section 43.6.5.5</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="PLPGSQL-PORTING-EXAMPLES"><div class="titlepage"><div><div><h3 class="title">43.13.1. Porting Examples <a href="#PLPGSQL-PORTING-EXAMPLES" class="id_link">#</a></h3></div></div></div><p>
<a class="xref" href="plpgsql-porting.html#PGSQL-PORTING-EX1" title="Example 43.9. Porting a Simple Function from PL/SQL to PL/pgSQL">Example 43.9</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 43.9. 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 43.10. Porting a Function that Creates Another Function from PL/SQL to PL/pgSQL">Example 43.10</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 43.10. 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 43.11. Porting a Procedure With String Manipulation and OUT Parameters from PL/SQL to PL/pgSQL">Example 43.11</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="43.13.3. Appendix">Section 43.13.3</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 43.11. 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 43.12. Porting a Procedure from PL/SQL to PL/pgSQL">Example 43.12</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 43.12. 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 > 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 $$
DECLARE
a_running_job_count integer;
BEGIN
LOCK TABLE cs_jobs IN EXCLUSIVE MODE;
SELECT count(*) INTO a_running_job_count FROM cs_jobs WHERE end_stamp IS NULL;
IF a_running_job_count > 0 THEN
COMMIT; -- free lock
RAISE EXCEPTION 'Unable to create a new job: a job is currently running'; -- <span id="co.plpgsql-porting-raise"></span>(1)
END IF;
DELETE FROM cs_active_job;
INSERT INTO cs_active_job(job_id) VALUES (v_job_id);
BEGIN
INSERT INTO cs_jobs (job_id, start_stamp) VALUES (v_job_id, now());
EXCEPTION
WHEN unique_violation THEN -- <span id="co.plpgsql-porting-exception"></span>(2)
-- don't worry if it already exists
END;
COMMIT;
END;
$$ 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">43.13.2. Other Things to Watch For <a href="#PLPGSQL-PORTING-OTHER" class="id_link">#</a></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">43.13.2.1. Implicit Rollback after Exceptions <a href="#PLPGSQL-PORTING-EXCEPTIONS" class="id_link">#</a></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="PLPGSQL-PORTING-OTHER-EXECUTE"><div class="titlepage"><div><div><h4 class="title">43.13.2.2. <code class="command">EXECUTE</code> <a href="#PLPGSQL-PORTING-OTHER-EXECUTE" class="id_link">#</a></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="43.5.4. Executing Dynamic Commands">Section 43.5.4</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">43.13.2.3. Optimizing <span class="application">PL/pgSQL</span> Functions <a href="#PLPGSQL-PORTING-OPTIMIZATION" class="id_link">#</a></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">43.13.3. Appendix <a href="#PLPGSQL-PORTING-APPENDIX" class="id_link">#</a></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 $$
DECLARE
pos integer NOT NULL DEFAULT 0;
temp_str varchar;
beg integer;
length integer;
ss_length integer;
BEGIN
IF beg_index > 0 THEN
temp_str := substring(string FROM beg_index);
pos := position(string_to_search_for IN temp_str);
IF pos = 0 THEN
RETURN 0;
ELSE
RETURN pos + beg_index - 1;
END IF;
ELSIF beg_index < 0 THEN
ss_length := char_length(string_to_search_for);
length := char_length(string);
beg := length + 1 + beg_index;
WHILE beg > 0 LOOP
temp_str := substring(string FROM beg FOR ss_length);
IF string_to_search_for = temp_str THEN
RETURN beg;
END IF;
beg := beg - 1;
END LOOP;
RETURN 0;
ELSE
RETURN 0;
END IF;
END;
$$ LANGUAGE plpgsql STRICT IMMUTABLE;
CREATE FUNCTION instr(string varchar, string_to_search_for varchar,
beg_index integer, occur_index integer)
RETURNS integer AS $$
DECLARE
pos integer NOT NULL DEFAULT 0;
occur_number integer NOT NULL DEFAULT 0;
temp_str varchar;
beg integer;
i integer;
length integer;
ss_length integer;
BEGIN
IF occur_index <= 0 THEN
RAISE 'argument ''%'' is out of range', occur_index
USING ERRCODE = '22003';
END IF;
IF beg_index > 0 THEN
beg := beg_index - 1;
FOR i IN 1..occur_index LOOP
temp_str := substring(string FROM beg + 1);
pos := position(string_to_search_for IN temp_str);
IF pos = 0 THEN
RETURN 0;
END IF;
beg := beg + pos;
END LOOP;
RETURN beg;
ELSIF beg_index < 0 THEN
ss_length := char_length(string_to_search_for);
length := char_length(string);
beg := length + 1 + beg_index;
WHILE beg > 0 LOOP
temp_str := substring(string FROM beg FOR ss_length);
IF string_to_search_for = temp_str THEN
occur_number := occur_number + 1;
IF occur_number = occur_index THEN
RETURN beg;
END IF;
END IF;
beg := beg - 1;
END LOOP;
RETURN 0;
ELSE
RETURN 0;
END IF;
END;
$$ 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" title="43.12. Tips for Developing in PL/pgSQL">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpgsql.html" title="Chapter 43. PL/pgSQL — SQL Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pltcl.html" title="Chapter 44. PL/Tcl — Tcl Procedural Language">Next</a></td></tr><tr><td width="40%" align="left" valign="top">43.12. Tips for Developing in <span class="application">PL/pgSQL</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="40%" align="right" valign="top"> Chapter 44. PL/Tcl — Tcl Procedural Language</td></tr></table></div></body></html>
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