From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | "Bryan White" <bryan(at)arcamax(dot)com> |
Cc: | "pgsql-general" <pgsql-general(at)postgreSQL(dot)org> |
Subject: | Re: Corrupt Table |
Date: | 2000-09-15 14:31:05 |
Message-ID: | 20227.969028265@sss.pgh.pa.us |
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Lists: | pgsql-general |
"Bryan White" <bryan(at)arcamax(dot)com> writes:
> I would still like to refine my pganal tool to look inside of tuples. Where
> should I look to find information about the internal structure? Is it
> parsable at some level on its own or do I have to consult the system tables
> to determine stucture. I suspect this might get more complicated once TOAST
> is available.
The tuple layout is basically
header
bitmap of which fields are null
values for non-null fields
The header is type HeapTupleHeaderData defined in
src/include/access/htup.h. The bitmap is omitted if the header's
infomask shows the tuple contains no nulls; otherwise its length
in bits is the same as the t_natts field of the header.
The data values are uninterpretable without looking up the set of
column datatypes for the table...
regards, tom lane
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