Re: avoid recasting text to tsvector when calculating selectivity

Tom Lane wrote:
> Jan Urbański <j.urbanski@students.mimuw.edu.pl> writes:
>> I'm about to write a oprrest function for the @@ operator. Currently @@ 
>> handles multiple cases, like tsvector @@ tsquery, text @@ tsquery, 
>> tsquery @@ tsvector etc. The text @@ text case is for instance handled 
>> by calling to_tsvector and plainto_tsquery on the input arguments.
> 
>> For a @@ restriction function, I need to have a tsquery and a tsvector, 
>> so in the text @@ text situation I'd end up calling plainto_tsquery 
>> during planning, which would consequently get called again during 
>> execution. Also, I'd need a not-so-elegant if-elsif-elsif sequence at 
>> the beginning of the function. Is this OK/unavoidable/easly avoided?
> 
> I'm not following your point here.  Sure, there are multiple flavors of
> @@, but why shouldn't they each have their own oprrest function?

Because they'll all boil down to the same function. Suppose I have an 
oprrest function for tsvector @@ tsquery. An oprrest for text @@ text 
would just be:
tv = DatumGetTSVector(DirectFunctionCall1(to_tsvector, PG_GETARG_DATUM(0)));
tq = DatumGetTSQuery(DirectFunctionCall1(plainto_tsquery, 
PG_GETARG_DATUM(1)));
res = DirectFunctionCall2(my_oprrest, TSVectorGetDatum(tv), 
TSQueryGetDatun(tq))
...

I thought I might avoid having to call ts_tsvector and plainto_tsquery, 
because the arguments need to be transformed to tsvector and tsquery 
anyway during execution.

-- 
Jan Urbanski
GPG key ID: E583D7D2

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