-Executes an SQL query. What the method does if the query fails depends
-on C<$may_fail>. If it is falsish then the method will simply die
-outputting the error message via L</db_error>. If C<$may_fail> is
-trueish then the current transaction will be rolled back, a new one
-will be started
+What the method does if the query fails depends on this parameter. If
+it is falsish (the default) then the method will simply die outputting
+the error message via L</db_error>. If C<may_fail> is trueish then the
+current transaction will be rolled back, a new one will be started.
+
+=item C<bind>
+
+An optional array reference containing bind parameter for the query.
+
+=item C<dbh>
+
+The database handle to use. If undefined then C<$self-E<gt>dbh> will
+be used.
+
+=back
+
+=item C<db_errstr [$handle]>
+
+Returns the last database from C<$handle> error message encoded in
+Perl's internal encoding. The PostgreSQL DBD before 2.16.1 leaves the
+UTF-8 flag off for error messages even if the C<pg_enable_utf8>
+attribute is set. For older versions the error string is already
+encoded correctly and is left unchanged.
+
+C<$handle> is optional and can be one of three things:
+
+=over 2
+
+=item 1. A database or statement handle. In that case
+C<$handle-E<gt>errstr> is used.
+
+=item 2. The string 'DBI'. In that case C<$DBI::errstr> is used.
+
+=item 3. If it is undefined then C<$self-E<gt>dbh-E<gt>errstr> is
+used.
+
+=back
+
+=item C<drop_constraints %params>
+
+Drops all constraints of a type (e.g. foreign keys) on a table. One
+parameter is mandatory: C<table>. Optional parameters include:
+
+=over 2
+
+=item * C<schema> -- if missing defaults to C<public>
+
+=item * C<type> -- if missing defaults to C<FOREIGN KEY>. Must be one of
+the values contained in the C<information_schema.table_constraints>
+view in the C<constraint_type> column.
+
+=back