Re: OCTET_LENGTH is wrong

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Peter Eisentraut <peter_e(at)gmx(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: OCTET_LENGTH is wrong
Date: 2001-11-19 18:28:31
Message-ID: 200111191828.fAJISVP07644@candle.pha.pa.us
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OK, I have applied this patch so text octet_length returns
non-compressed length of data, to match octet_length of other types.

I also removed the XXX comments added by Tom.

---------------------------------------------------------------------------

> > I think "the value of S" implies "the user-accessible representation of
> > the value of S", in the sense, "How much memory do I need to allocate to
> > store this value".
> >
> > Furthermore, the size of the TOAST representation that is returned now is
> > just one particular of several intermediate representations. For
> > instance, it does not include the VARHDRSZ and it does not include the
> > size of the tuple headers when it's stored externally. Thus, this size is
> > heavily skewed toward low numbers and doesn't tell you much about either
> > the disk end or the user's end.
>
> Yes, good arguments. If we want to implement storage_length at some
> later time, I think the compressed length may be appropriate, but for
> general use, I think we need to return the uncompressed length,
> especially considering that multibyte makes the ordinary 2length return
> number of characters, so users need a way to get byte length.
>
> Attached is a patch that makes text return the same value type as char()
> and varchar() already do. As Tatsuo pointed out, they were
> inconsistent. All the other octet_length() functions look fine so it
> was only text that had this problem.
>
> --
> Bruce Momjian | http://candle.pha.pa.us
> pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
> + If your life is a hard drive, | 830 Blythe Avenue
> + Christ can be your backup. | Drexel Hill, Pennsylvania 19026

> Index: src/backend/utils/adt/varlena.c
> ===================================================================
> RCS file: /cvsroot/pgsql/src/backend/utils/adt/varlena.c,v
> retrieving revision 1.74
> diff -c -r1.74 varlena.c
> *** src/backend/utils/adt/varlena.c 2001/10/25 05:49:46 1.74
> --- src/backend/utils/adt/varlena.c 2001/11/18 19:11:52
> ***************
> *** 273,284 ****
> Datum
> textoctetlen(PG_FUNCTION_ARGS)
> {
> ! struct varattrib *t = (struct varattrib *) PG_GETARG_RAW_VARLENA_P(0);
>
> ! if (!VARATT_IS_EXTERNAL(t))
> ! PG_RETURN_INT32(VARATT_SIZE(t) - VARHDRSZ);
> !
> ! PG_RETURN_INT32(t->va_content.va_external.va_extsize);
> }
>
> /*
> --- 273,281 ----
> Datum
> textoctetlen(PG_FUNCTION_ARGS)
> {
> ! text *arg = PG_GETARG_VARCHAR_P(0);
>
> ! PG_RETURN_INT32(VARSIZE(arg) - VARHDRSZ);
> }
>
> /*

>
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--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026

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