Re: Doing better at HINTing an appropriate column within errorMissingColumn()

Peter Geoghegan wrote:
> With the addition of LATERAL subqueries, Tom fixed up the mechanism
> for keeping track of which relations are visible for column references
> while the FROM clause is being scanned. That allowed
> errorMissingColumn() to give a more useful error to the one produced
> by the prior coding of that mechanism, with an errhint sometimes
> proffering: 'There is a column named "foo" in table "bar", but it
> cannot be referenced from this part of the query'.
> 
> I wondered how much further this could be taken. Attached patch
> modifies contrib/fuzzystrmatch, moving its Levenshtein distance code
> into core without actually moving the relevant SQL functions too. That
> change allowed me to modify errorMissingColumn() to make more useful
> suggestions as to what might have been intended under other
> circumstances, like when someone fat-fingers a column name.

> [local]/postgres=# select * from orders o join orderlines ol on o.orderid = ol.orderids limit 1;
> ERROR:  42703: column ol.orderids does not exist
> LINE 1: ...* from orders o join orderlines ol on o.orderid = ol.orderid...
>                                                              ^
> HINT:  Perhaps you meant to reference the column "ol"."orderid".

This sounds like a mild version of DWIM:
http://www.jargondb.org/glossary/dwim

Maybe it is just me, but I get uncomfortable when a program tries
to second-guess what I really want.

Yours,
Laurenz Albe