Re: Where are the detoast function called in select * from table_name case?

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От Pavel Stehule
Тема Re: Where are the detoast function called in select * from table_name case?
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Msg-id CAFj8pRCONBsoZMv4sT=9cSq9=Vc0AQsMvLw6JuENhSsE7CboHg@mail.gmail.com
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Ответ на Where are the detoast function called in select * from table_name case?  (Rui Hai Jiang <ruihaijiang@msn.com>)
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Hi

Depends on usage, but often times the detoasting is called from DatumGet***** macros

The values are detoasted only when it is required

#define PG_GETARG_TEXT_PP(n)   DatumGetTextPP(PG_GETARG_DATUM(n))
#define DatumGetTextPP(X)              ((text *) PG_DETOAST_DATUM_PACKED(X))
#define PG_DETOAST_DATUM(datum)   >pg_detoast_datum((struct varlena *) DatumGetPointer(datum))

Regards

Pavel Stehule

2015-05-06 15:00 GMT+02:00 Rui Hai Jiang <ruihaijiang@msn.com>:
Hello,

I've been reading the PostgreSQL code for weeks to figure out how TOAST works.
I couldn't find where are the TOAST function called to detoast a tuple comes from a select query, for example, select * from table_name.
Does anyone know this? Can you give me some help? And any help would save me a lot of time.

Thanks,
Rui Hai



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