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Add BufFileRead variants with short read and EOF detection

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Most callers of BufFileRead() want to check whether they read the full
specified length.  Checking this at every call site is very tedious.
This patch provides additional variants BufFileReadExact() and
BufFileReadMaybeEOF() that include the length checks.

I considered changing BufFileRead() itself, but this function is also
used in extensions, and so changing the behavior like this would
create a lot of problems there.  The new names are analogous to the
existing LogicalTapeReadExact().

Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/f3501945-c591-8cc3-5ef0-b72a2e0eaa9c@enterprisedb.com
This commit is contained in:
Peter Eisentraut
2023-01-16 09:20:44 +01:00
parent 1561612e3b
commit 20428d344a
9 changed files with 73 additions and 134 deletions
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18
src/backend/executor/nodeHashjoin.c
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@ -1260,28 +1260,18 @@ ExecHashJoinGetSavedTuple(HashJoinState *hjstate,
* we can read them both in one BufFileRead() call without any type
* cheating.
*/
nread = BufFileRead(file, header, sizeof(header));
nread = BufFileReadMaybeEOF(file, header, sizeof(header), true);
if (nread == 0) /* end of file */
{
ExecClearTuple(tupleSlot);
return NULL;
}
if (nread != sizeof(header))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from hash-join temporary file: read only %zu of %zu bytes",
nread, sizeof(header))));
*hashvalue = header[0];
tuple = (MinimalTuple) palloc(header[1]);
tuple->t_len = header[1];
nread = BufFileRead(file,
((char *) tuple + sizeof(uint32)),
header[1] - sizeof(uint32));
if (nread != header[1] - sizeof(uint32))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from hash-join temporary file: read only %zu of %zu bytes",
nread, header[1] - sizeof(uint32))));
BufFileReadExact(file,
(char *) tuple + sizeof(uint32),
header[1] - sizeof(uint32));
ExecForceStoreMinimalTuple(tuple, tupleSlot, true);
return tupleSlot;
}