From: | Christoph Berg <myon(at)debian(dot)org> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: VARDATA_COMPRESSED_GET_COMPRESS_METHOD comment? |
Date: | 2021-09-08 15:33:22 |
Message-ID: | YTjXwhKH/4J6U48u@msg.df7cb.de |
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Lists: | pgsql-hackers |
Re: Robert Haas
> But I agree with you that referring to the argument to
> VARDATA_COMPRESSED_GET_EXTSIZE or
> VARDATA_COMPRESSED_GET_COMPRESS_METHOD as an "external compressed
> Datum" doesn't seem quite right. It is compressed, but it is not
> external, at least in the sense that I understand that term.
How about "compressed-in-line Datum" like on the comment 5 lines above?
/* caution: this will not work on an external or compressed-in-line Datum */
/* caution: this will return a possibly unaligned pointer */
#define VARDATA_ANY(PTR) \
(VARATT_IS_1B(PTR) ? VARDATA_1B(PTR) : VARDATA_4B(PTR))
/* Decompressed size and compression method of an external compressed Datum */
#define VARDATA_COMPRESSED_GET_EXTSIZE(PTR) \
(((varattrib_4b *) (PTR))->va_compressed.va_tcinfo & VARLENA_EXTSIZE_MASK)
#define VARDATA_COMPRESSED_GET_COMPRESS_METHOD(PTR) \
(((varattrib_4b *) (PTR))->va_compressed.va_tcinfo >> VARLENA_EXTSIZE_BITS)
This "external" there cost me about one hour of extra poking around
until I realized this is actually the macro I wanted.
-> /* Decompressed size and compression method of a compressed-in-line Datum */
Christoph
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