Revise plpgsql's scanner to process comments and string literals in a way

more nearly matching the core SQL scanner.  The user-visible effects are:

* Block comments (slash-star comments) now nest, as per SQL spec.

* In standard_conforming_strings mode, backslash as the last character of a
  non-E string literal is now correctly taken as an ordinary character;
  formerly it was misinterpreted as escaping the ending quote.  (Since the
  string also had to pass through the core scanner, this invariably led
  to syntax errors.)

* Formerly, backslashes in the format string of RAISE were always treated as
  quoting the next character, regardless of mode.  Now, they are ordinary
  characters with standard_conforming_strings on, while with it off, they
  introduce the same set of escapes as in the core SQL scanner.  Also,
  escape_string_warning is now effective for RAISE format strings.  These
  changes make RAISE format strings work just like any other string literal.

This is implemented by copying and pasting a lot of logic from the core
scanner.  It would be a good idea to look into getting rid of plpgsql's
scanner entirely in favor of using the core scanner.  However, that involves
more change than I can justify making during beta --- in particular, the core
scanner would have to become re-entrant.

In passing, remove the kluge that made the plpgsql scanner emit T_FUNCTION or
T_TRIGGER as a made-up first token.  That presumably had some value once upon
a time, but now it's just useless complication for both the scanner and the
grammar.

1 files changed, 3 insertions, 5 deletions

diff --git a/doc/src/sgml/plpgsql.sgml b/doc/src/sgml/plpgsql.sgml
index 6eb9b2b9e7..319547ec00 100644
--- a/doc/src/sgml/plpgsql.sgml
+++ b/doc/src/sgml/plpgsql.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.139 2009/04/02 19:20:45 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.140 2009/04/19 18:52:56 tgl Exp $ -->
 
 <chapter id="plpgsql">
   <title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title>
@@ -220,10 +220,8 @@ END <optional> <replaceable>label</replaceable> </optional>;
      There are two types of comments in <application>PL/pgSQL</>. A double
      dash (<literal>--</literal>) starts a comment that extends to the end of
      the line. A <literal>/*</literal> starts a block comment that extends to
-     the next occurrence of <literal>*/</literal>.  Block comments cannot be
-     nested, but double dash comments can be enclosed into a block comment and
-     a double dash can hide the block comment delimiters <literal>/*</literal>
-     and <literal>*/</literal>.
+     the next occurrence of <literal>*/</literal>.  Block comments nest,
+     just as in ordinary SQL.
     </para>
 
     <para>