Horton

Re: Re: pg_stat_statements normalisation without invasive changes to the parser (was: Next steps on pg_stat_statements normalisation)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Geoghegan <peter@2ndquadrant.com>
Cc: PG Hackers <pgsql-hackers@postgresql.org>
Date: 2012-02-21T01:48:30Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Restructure SELECT INTO's parsetree representation into CreateTableAsStmt.

  2. Extend the parser location infrastructure to include a location field in

  3. Teach eval_const_expressions() to simplify an ArrayCoerceExpr to a constant

Peter Geoghegan <peter@2ndquadrant.com> writes:
> Here is the single, hacky change I've made just for now to the core
> parser to quickly see if it all works as expected:

> *************** transformTypeCast(ParseState *pstate, Ty
> *** 2108,2113 ****
> --- 2108,2116 ----
>   	if (location < 0)
>   		location = tc->typeName->location;

> + 	if (IsA(expr, Const))
> + 		location = ((Const*)expr)->location;
> +
>   	result = coerce_to_target_type(pstate, expr, inputType,
>   								   targetType, targetTypmod,
>   								   COERCION_EXPLICIT,

This does not look terribly sane to me.  AFAICS, the main effect of this
would be that if you have an error in coercing a literal to some
specified type, the error message would point at the literal and not
at the cast operator.  That is, in examples like these:

regression=# select 42::point;
ERROR:  cannot cast type integer to point
LINE 1: select 42::point;
                 ^
regression=# select cast (42 as point);
ERROR:  cannot cast type integer to point
LINE 1: select cast (42 as point);
               ^

you're proposing to move the error pointer to the "42", and that does
not seem like an improvement, especially not if it only happens when the
cast subject is a simple constant rather than an expression.

			regards, tom lane