Pg: Add escape_literal() and escape_identifier()

Didn't expect I'd ever need these, but they're useful for generating SQL
scripts.

FU.xs

@@ -216,6 +216,24 @@ void status(fupg_conn *c)
   CODE:
     ST(0) = sv_2mortal(newSVpv(fupg_conn_status(c), 0));
 
+void escape_literal(fupg_conn *c, SV *v)
+  CODE:
+    STRLEN len;
+    const char *str = SvPVutf8(v, len);
+    char *r = PQescapeLiteral(c->conn, str, len);
+    if (!r) fupg_conn_croak(c, "escapeLiteral");
+    ST(0) = newSVpvn_flags(r, strlen(r), SVf_UTF8|SVs_TEMP);
+    PQfreemem(r);
+
+void escape_identifier(fupg_conn *c, SV *v)
+  CODE:
+    STRLEN len;
+    const char *str = SvPVutf8(v, len);
+    char *r = PQescapeIdentifier(c->conn, str, len);
+    if (!r) fupg_conn_croak(c, "escapeIdentifier");
+    ST(0) = newSVpvn_flags(r, strlen(r), SVf_UTF8|SVs_TEMP);
+    PQfreemem(r);
+
 void cache(fupg_conn *x, ...)
   ALIAS:
     FU::Pg::conn::text_params  = FUPG_TEXT_PARAMS

FU/Pg.pm

@@ -123,6 +123,17 @@ Connection is dead or otherwise unusable.
 
 =back
 
+=item $conn->escape_literal($str)
+
+Return an escaped version of C<$str> suitable for use as a string literal in an
+SQL statement. You'll rarely need this, it's often better to pass data as bind
+parameters instead.
+
+=item $conn->escape_identifier($str)
+
+Return an escaped version of C<$str> suitable for use as an identifier (name of
+a table, column, function, etc) in an SQL statement.
+
 =item $conn->cache($enable)
 
 =item $conn->text_params($enable)

c/libpq.h

@@ -43,6 +43,8 @@ typedef enum { PQTRANS_IDLE, PQTRANS_ACTIVE, PQTRANS_INTRANS, PQTRANS_INERROR, P
     X(PQconnectdb, PGconn *, const char *) \
     X(PQenterPipelineMode, int, PGconn *) \
     X(PQerrorMessage, char *, const PGconn *) \
+    X(PQescapeIdentifier, char *, PGconn *, const char *, size_t) \
+    X(PQescapeLiteral, char *, PGconn *, const char *, size_t) \
     X(PQexec, PGresult *, PGconn *, const char *) \
     X(PQexecParams, PGresult *, PGconn *, const char *, int, const Oid *, const char * const *, const int *, const int *, int) \
     X(PQexecPrepared, PGresult *, PGconn *, const char *, int, const char * const *, const int *, const int *, int) \

t/pgconnect.t

@@ -353,6 +353,16 @@ subtest 'txn', sub {
     is_deeply $st->val, [1,3], 'not deep copy';
 }
 
+
+{
+    # Exact format returned by escape_literal() can differ between Postgres versions and configurations.
+    my $x = q{"' \" \\};
+    is $conn->q('SELECT '.$conn->escape_literal($x))->val, $x;
+
+    # Format can also change, but unsure how to test this otherwise.
+    is $conn->escape_identifier('hel\l"o'), '"hel\l""o"';
+}
+
 subtest 'Prepared statement cache', sub {
     my $txn = $conn->cache_size(2)->txn->cache;
     my sub numexec($sql) {