Dollar quoting docs, round 1

David Fetter wrote:

Kind people,

Please find attached a diff to the SGML docs that attempts to go over
the new dollar quoting feature.

I think we should just use $$ in each case. Otherwise it might look
more complicated than before.

On Wed, Apr 28, 2004 at 08:28:58AM +0200, Peter Eisentraut wrote:

David Fetter wrote:

Kind people,

Please find attached a diff to the SGML docs that attempts to go
over the new dollar quoting feature.

I think we should just use $$ in each case. Otherwise it might look
more complicated than before.

Peter,

I'd be delighted to simplify some of the quotes. They can't all be $$
because of the nesting, so that's out. Also, I believe it is a good
idea to give some idea of what is going on with the tags, as I do with
similar structures in other languages. For example, when I am writing
up a piece of SQL in perl or php, the tag looks like this:

$sql = <<SQL
...
SQL

$sql = <<<SQL
...
SQL;

Thanks as always for your prompt insights.

Cheers,
D
--
David Fetter david@fetter.org http://fetter.org/
phone: +1 510 893 6100 mobile: +1 415 235 3778

Remember to vote!

Peter Eisentraut wrote:

David Fetter wrote:

Kind people,

Please find attached a diff to the SGML docs that attempts to go over
the new dollar quoting feature.

I think we should just use $$ in each case. Otherwise it might look
more complicated than before.

Agreed. I was worried about dollar arguments in functions, e.g. $1:

test=> select $$$1$$;
?column?
----------
$1
(1 row)

but that seems to be OK. Is our only problem actual $$ in a function
body? And there is no way of escaping that, right? They have to choose
a different quote characters sequence.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

David Fetter wrote:

On Wed, Apr 28, 2004 at 08:28:58AM +0200, Peter Eisentraut wrote:

David Fetter wrote:

Kind people,

Please find attached a diff to the SGML docs that attempts to go
over the new dollar quoting feature.

I think we should just use $$ in each case. Otherwise it might look
more complicated than before.

Peter,

I'd be delighted to simplify some of the quotes. They can't all be $$
because of the nesting, so that's out. Also, I believe it is a good
idea to give some idea of what is going on with the tags, as I do with
similar structures in other languages. For example, when I am writing
up a piece of SQL in perl or php, the tag looks like this:

$sql = <<SQL
...
SQL

$sql = <<<SQL
...
SQL;

Interesting, but I think most people like to use a tag that identifies
what is happening, rather than the content. I think that's why <<END is
used frequently, so END appears as the end. Seeing SQL alone on a line
seems strange.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Bruce Momjian wrote:

David Fetter wrote:

On Wed, Apr 28, 2004 at 08:28:58AM +0200, Peter Eisentraut wrote:

David Fetter wrote:

Kind people,

Please find attached a diff to the SGML docs that attempts to go
over the new dollar quoting feature.

I think we should just use $$ in each case. Otherwise it might look
more complicated than before.

Peter,

I'd be delighted to simplify some of the quotes. They can't all be $$
because of the nesting, so that's out. Also, I believe it is a good
idea to give some idea of what is going on with the tags, as I do with
similar structures in other languages. For example, when I am writing
up a piece of SQL in perl or php, the tag looks like this:

$sql = <<SQL
...
SQL

$sql = <<<SQL
...
SQL;

Interesting, but I think most people like to use a tag that identifies
what is happening, rather than the content. I think that's why <<END is
used frequently, so END appears as the end. Seeing SQL alone on a line
seems strange.

I typically combine these approaches, with a heredoc marker like EOSQL

cheers

andrew

On Wed, Apr 28, 2004 at 12:30:06PM -0400, Bruce Momjian wrote:

Peter Eisentraut wrote:

David Fetter wrote:

Kind people,

Please find attached a diff to the SGML docs that attempts to go over
the new dollar quoting feature.

I think we should just use $$ in each case. Otherwise it might look
more complicated than before.

Agreed. I was worried about dollar arguments in functions, e.g. $1:

test=> select $$$1$$;
?column?
----------
$1
(1 row)

but that seems to be OK. Is our only problem actual $$ in a
function body?

This is a design feature, as I understand it.

And there is no way of escaping that, right?

Right.

They have to choose a different quote characters sequence.

Yes. Here is a short, but (IMHO) useful example. Incidentally, I
have not yet found a way to get it working in versions prior to CVS
HEAD.

CREATE OR REPLACE FUNCTION has_bad_chars(TEXT) RETURNS BOOLEAN AS
$function$
BEGIN
RETURN ($1 ~ $q$[\t\r\n\v|\\]$q$);
END;
$function$ LANGUAGE plpgsql;

Cheers,
D
--
David Fetter david@fetter.org http://fetter.org/
phone: +1 510 893 6100 mobile: +1 415 235 3778

Remember to vote!

Bruce Momjian wrote:

Peter Eisentraut wrote:

David Fetter wrote:

Kind people,

Please find attached a diff to the SGML docs that attempts to go over
the new dollar quoting feature.

I think we should just use $$ in each case. Otherwise it might look
more complicated than before.

Agreed. I was worried about dollar arguments in functions, e.g. $1:

test=> select $$$1$$;
?column?
----------
$1
(1 row)

but that seems to be OK. Is our only problem actual $$ in a function
body? And there is no way of escaping that, right? They have to choose
a different quote characters sequence.

The string inside $x$ is totally opaque and unescaped. The restriction
on markers is that the string mustn't contain $x$, and mustn't end with
$x, i.e., the scanners see $x$ and simply accumulate all the characters
in the string until they see $x$ again - all 3 scanners (postgres, psql,
plpgsql) work the same way on this.

Functions with arguments might need to be quoted with something other
than plain $$, and in any case if their bodies make use of $$ they
certainly will. pg_dump's approach to quoting function bodies is to
start with $$ and then generate longer and longer markers until the
marker without trailing $ is not found in the string comprising the
function body. In most cases it ends up using $_$.

I hope that makes things clearer.

cheers

andrew