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Add documentation for the new "dollar quoting" feature, and update existing

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examples to use dollar quoting when appropriate. Original patch from David
Fetter, additional work and editorializing by Neil Conway.
This commit is contained in:
Neil Conway
2004-05-16 23:22:08 +00:00
parent 2871f60f23
commit 8295c27c89
11 changed files with 371 additions and 253 deletions
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46
doc/src/sgml/pltcl.sgml
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@@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.29 2004/01/24 23:06:29 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.30 2004/05/16 23:22:07 neilc Exp $
-->
<chapter id="pltcl">
@@ -77,9 +77,10 @@ $PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.29 2004/01/24 23:06:29 tgl Exp $
To create a function in the <application>PL/Tcl</> language, use the standard syntax:
<programlisting>
CREATE FUNCTION <replaceable>funcname</replaceable> (<replaceable>argument-types</replaceable>) RETURNS <replaceable>return-type</replaceable> AS '
CREATE FUNCTION <replaceable>funcname</replaceable>
(<replaceable>argument-types</replaceable>) RETURNS <replaceable>return-type</replaceable> AS $$
# PL/Tcl function body
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
<application>PL/TclU</> is the same, except that the language has to be specified as
@@ -100,10 +101,10 @@ CREATE FUNCTION <replaceable>funcname</replaceable> (<replaceable>argument-types
returning the greater of two integer values could be defined as:
<programlisting>
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS $$
if {$1 > $2} {return $1}
return $2
' LANGUAGE pltcl STRICT;
$$ LANGUAGE pltcl STRICT;
</programlisting>
Note the clause <literal>STRICT</>, which saves us from
@@ -122,7 +123,7 @@ CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
argument, rather than null:
<programlisting>
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS $$
if {[argisnull 1]} {
if {[argisnull 2]} { return_null }
return $2
@@ -130,7 +131,7 @@ CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
if {[argisnull 2]} { return $1 }
if {$1 > $2} {return $1}
return $2
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
</para>
@@ -154,7 +155,7 @@ CREATE TABLE employee (
age integer
);
CREATE FUNCTION overpaid(employee) RETURNS boolean AS '
CREATE FUNCTION overpaid(employee) RETURNS boolean AS $$
if {200000.0 < $1(salary)} {
return "t"
}
@@ -162,7 +163,7 @@ CREATE FUNCTION overpaid(employee) RETURNS boolean AS '
return "t"
}
return "f"
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
</para>
@@ -359,25 +360,24 @@ spi_exec -array C "SELECT * FROM pg_class" {
Here's an example of a PL/Tcl function using a prepared plan:
<programlisting>
CREATE FUNCTION t1_count(integer, integer) RETURNS integer AS '
CREATE FUNCTION t1_count(integer, integer) RETURNS integer AS $$
if {![ info exists GD(plan) ]} {
# prepare the saved plan on the first call
set GD(plan) [ spi_prepare \\
"SELECT count(*) AS cnt FROM t1 WHERE num &gt;= \\$1 AND num &lt;= \\$2" \\
set GD(plan) [ spi_prepare \
"SELECT count(*) AS cnt FROM t1 WHERE num &gt;= \$1 AND num &lt;= \$2" \
[ list int4 int4 ] ]
}
spi_execp -count 1 $GD(plan) [ list $1 $2 ]
return $cnt
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
Note that each backslash that Tcl should see must be doubled when
we type in the function, since the main parser processes
backslashes, too, in <command>CREATE FUNCTION</>. We need backslashes inside
the query string given to <function>spi_prepare</> to ensure that
the <literal>$<replaceable>n</replaceable></> markers will be passed through to
<function>spi_prepare</> as-is, and not
replaced by Tcl variable substitution.
We need backslashes inside the query string given to
<function>spi_prepare</> to ensure that the
<literal>$<replaceable>n</replaceable></> markers will be passed
through to <function>spi_prepare</> as-is, and not replaced by Tcl
variable substitution.
</para>
</listitem>
</varlistentry>
@@ -425,7 +425,7 @@ SELECT 'doesn't' AS ret
The submitted command should contain
<programlisting>
SELECT 'doesn''t' AS ret
SELECT $q$doesn't$q$ AS ret
</programlisting>
which can be formed in PL/Tcl using
@@ -611,7 +611,7 @@ SELECT 'doesn''t' AS ret
incremented on every update operation.
<programlisting>
CREATE FUNCTION trigfunc_modcount() RETURNS trigger AS '
CREATE FUNCTION trigfunc_modcount() RETURNS trigger AS $$
switch $TG_op {
INSERT {
set NEW($1) 0
@@ -625,7 +625,7 @@ CREATE FUNCTION trigfunc_modcount() RETURNS trigger AS '
}
}
return [array get NEW]
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
CREATE TABLE mytab (num integer, description text, modcnt integer);