On Mon, Nov 17, 2014 at 3:04 PM, Peter Geoghegan <p...@heroku.com> wrote: > postgres=# select qty from orderlines ; > ERROR: 42703: column "qty" does not exist > LINE 1: select qty from orderlines ; > ^ > HINT: Perhaps you meant to reference the column "orderlines"."quantity". > """
I don't buy this example, because it would give you the same hint if you told it you wanted to access a column called ant, or uay, or tit. And that's clearly ridiculous. The reason why quantity looks like a reasonable suggestion for qty is because it's a conventional abbreviation, but an extremely high percentage of comparable cases won't be. >> + /* >> + * Charge extra (for inexact matches only) when an alias was >> + * specified that differs from what might have been used to >> + * correctly qualify this RTE's closest column >> + */ >> + if (wrongalias) >> + rtestate.distance += 3; >> >> I don't understand what situation this is catering to. Can you >> explain? It seems to account for a good deal of complexity. > > Two cases: > > 1. Distinguishing between the case where there was an exact match to a > column that isn't visible (i.e. the existing reason for > errorMissingColumn() to call here), and the case where there is a > visible column, but our alias was the wrong one. I guess that could > live in errorMissingColumn(), but overall it's more convenient to do > it here, so that errorMissingColumn() handles things almost uniformly > and doesn't really have to care. > > 2. For non-exact (fuzzy) matches, it seems more useful to give one > match rather than two when the user gave an alias that matches one > particular RTE. Consider this: > > """ > postgres=# select ordersid from orders o join orderlines ol on > o.orderid = ol.orderid; > ERROR: 42703: column "ordersid" does not exist > LINE 1: select ordersid from orders o join orderlines ol on o.orderi... > ^ > HINT: Perhaps you meant to reference the column "o"."orderid" or the > column "ol"."orderid". > LOCATION: errorMissingColumn, parse_relation.c:3166 > > postgres=# select ol.ordersid from orders o join orderlines ol on > o.orderid = ol.orderid; > ERROR: 42703: column ol.ordersid does not exist > LINE 1: select ol.ordersid from orders o join orderlines ol on o.ord... > ^ > HINT: Perhaps you meant to reference the column "ol"."orderid". > LOCATION: errorMissingColumn, parse_relation.c:3147 > """ I guess I'm confused at a broader level. If the alias is wrong, why are we considering names in this RTE *at all*? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
