9.5.1 standard conforming strings

Starting with PostgreSQL 8.2, there is a configuration file and runtime parameter standard_conforming_strings that controls how strictly the server parses SQL string syntax. When its value is on, strings that include the ‘\’ (backslash) character must be prefixed with ‘E’. Even when it is off, the server may emit a warning, anyway. To avoid such unpleasantness, Guile-PG provides sql-quote-auto-E?.

Fluid: sql-quote-auto-E? ¶

When non-#f, sql-quote will prefix a ‘E’ if it detects any ‘\’ (backslash) characters in its arg. For example:

(define (e.g.)
  (display (sql-quote "a\\b")))

(fluid-ref sql-quote-auto-E?)
⇒ #f

(e.g.)
-| 'a\134b'

(with-fluids ((sql-quote-auto-E? #t))
  (e.g.))
-| E'a\134b'

If there are no backslash characters, this has no effect.

The typical way to use this is to set the fluid soon after you make the connection and forget about it:

(and (pg-parameter-status CONN 'standard_conforming_strings)
     ;; Don't bother checking the parameter value;
     ;; enable functionality unconditionally.
     (fluid-set! sql-quote-auto-E? #t))

This can get hairy if you maintain more than one connection at a time to servers with mixed support for standard_conforming_strings, however (i.e., pre-8.2 and 8.2+ together). In that case, it is better to use with-fluids to enable the functionality completely dynamically.