Function PQfnumber

src/interfaces/libpq/fe-exec.c:3394–3489

* PQfnumber: find column number given column name * * The column name is parsed as if it were in a SQL statement, including * case-folding and double-quote processing. But note a possible gotcha: * downcasing in the frontend might follow different locale rules than * downcasing in the backend... * * Returns -1 if no match. In the present backend it is also possible * to have multiple mat

 * to have multiple matches, in which case the first one is found.
 */
int
PQfnumber(const PGresult *res, const char *field_name)
{
	char	   *field_case;
	bool		in_quotes;
	bool		all_lower = true;
	const char *iptr;
	char	   *optr;
	int			i;

	if (!res)
		return -1;

	/*
	 * Note: it is correct to reject a zero-length input string; the proper
	 * input to match a zero-length field name would be "".
	 */
	if (field_name == NULL ||
		field_name[0] == '\0' ||
		res->attDescs == NULL)
		return -1;

	/*
	 * Check if we can avoid the strdup() and related work because the
	 * passed-in string wouldn't be changed before we do the check anyway.
	 */
	for (iptr = field_name; *iptr; iptr++)
	{
		char		c = *iptr;

		if (c == '"' || c != pg_tolower((unsigned char) c))
		{
			all_lower = false;
			break;
		}
	}

	if (all_lower)
		for (i = 0; i < res->numAttributes; i++)
			if (strcmp(field_name, res->attDescs[i].name) == 0)
				return i;

	/* Fall through to the normal check if that didn't work out. */

	/*
	 * Note: this code will not reject partially quoted strings, eg
	 * foo"BAR"foo will become fooBARfoo when it probably ought to be an error
	 * condition.
	 */
	field_case = strdup(field_name);
	if (field_case == NULL)
		return -1;				/* grotty */

	in_quotes = false;
	optr = field_case;
	for (iptr = field_case; *iptr; iptr++)
	{
		char		c = *iptr;