Re: [Fwd: Re: [Pljava-dev] char with trailing space, PreparedStatement.setObject

[Thomas Hallgren <thomas(at)tada(dot)se>]

Tom Lane wrote:
> Thomas Hallgren <thomas(at)tada(dot)se> writes:
>   
> > so why does it make a difference to use varchar instead of text?
> >     
>
> It's a question of type resolution rules.  text is the preferred string
> type so it "wins" in cross-type situations, in particular
> 	char_value = text_value
> will be interpreted as
> 	char_value::text text_eq text_value
> varchar is not only not a preferred type, it doesn't even have any
> comparison ops of its own (it depends on text's ops).  Therefore given
> 	char_value = varchar_value
> the parser is faced with the alternative interpretations
> 	char_value::text text_eq varchar_value::text
> 	char_value char_eq varchar_value::char
> and it will prefer the latter because it has fewer casts.
> See
> http://www.postgresql.org/docs/8.1/static/typeconv.html
> particularly rules 10.2.3b and 3c.  The upshot of all this
> is that a parameter specified as "text" dominates any comparison
> to other string datatypes, whereas one specified as "varchar"
> does not.  Yeah, it's a bit grotty, but it gets the job done
> and it's not an area we're likely to change much.
>
> 			regards, tom lane
>   
Hmm, OK. I checked my code and I don't use any specific type. Instead, I 
use SPI_getargtypeid(ePlan, idx) on the prepared query and the 
pgType->typinput function of the type that corresponds to the returned 
oid. Perhaps the SPI_getargtypeid should return varchar for all text types?

Regards,
Thomas Hallgren