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Update buffile.h/.c comments for removal of non-temp option.

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Commit 11e264517 removed BufFile's isTemp flag, thereby eliminating
the possibility of resurrecting BufFileCreate().  But it left that
function in place, as well as a bunch of comments describing how things
worked for the non-temp-file case.  At best, that's now a source of
confusion.  So remove the long-since-commented-out function and change
relevant comments.

I (tgl) wanted to rename BufFileCreateTemp() to BufFileCreate(), but
that seems not to be the consensus position, so leave it as-is.

In passing, fix commit f0828b2fc's failure to update BufFileSeek's
comment to match the change of its argument type from long to off_t.
(I think that might actually have been intentional at the time, but
now that 64-bit off_t is nearly universal, it looks anachronistic.)

Thomas Munro and Tom Lane

Discussion: https://postgr.es/m/E1eFVyl-0008J1-RO@gemulon.postgresql.org
This commit is contained in:
Tom Lane 2017-11-25 13:19:43 -05:00
parent df3a66e282
commit ab97aaac8f
2 changed files with 10 additions and 30 deletions
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38
src/backend/storage/file/buffile.c
View File

@ -1,7 +1,7 @@
/*-------------------------------------------------------------------------
*
* buffile.c
* Management of large buffered files, primarily temporary files.
* Management of large buffered temporary files.
*
* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
@ -20,8 +20,8 @@
* of opening/closing file descriptors.
*
* Note that BufFile structs are allocated with palloc(), and therefore
* will go away automatically at transaction end. If the underlying
* virtual File is made with OpenTemporaryFile, then all resources for
* will go away automatically at query/transaction end. Since the underlying
* virtual Files are made with OpenTemporaryFile, all resources for
* the file are certain to be cleaned up even if processing is aborted
* by ereport(ERROR). The data structures required are made in the
* palloc context that was current when the BufFile was created, and
@ -45,8 +45,8 @@
/*
* We break BufFiles into gigabyte-sized segments, regardless of RELSEG_SIZE.
* The reason is that we'd like large temporary BufFiles to be spread across
* multiple tablespaces when available.
* The reason is that we'd like large BufFiles to be spread across multiple
* tablespaces when available.
*/
#define MAX_PHYSICAL_FILESIZE 0x40000000
#define BUFFILE_SEG_SIZE (MAX_PHYSICAL_FILESIZE / BLCKSZ)
@ -175,21 +175,6 @@ BufFileCreateTemp(bool interXact)
return file;
}
#ifdef NOT_USED
/*
* Create a BufFile and attach it to an already-opened virtual File.
*
* This is comparable to fdopen() in stdio. This is the only way at present
* to attach a BufFile to a non-temporary file. Note that BufFiles created
* in this way CANNOT be expanded into multiple files.
*/
BufFile *
BufFileCreate(File file)
{
return makeBufFile(file);
}
#endif
/*
* Close a BufFile
*
@ -202,7 +187,7 @@ BufFileClose(BufFile *file)
/* flush any unwritten data */
BufFileFlush(file);
/* close the underlying file(s) (with delete if it's a temp file) */
/* close and delete the underlying file(s) */
for (i = 0; i < file->numFiles; i++)
FileClose(file->files[i]);
/* release the buffer space */
@ -225,10 +210,6 @@ BufFileLoadBuffer(BufFile *file)
/*
* Advance to next component file if necessary and possible.
*
* This path can only be taken if there is more than one component, so it
* won't interfere with reading a non-temp file that is over
* MAX_PHYSICAL_FILESIZE.
*/
if (file->curOffset >= MAX_PHYSICAL_FILESIZE &&
file->curFile + 1 < file->numFiles)
@ -298,8 +279,7 @@ BufFileDumpBuffer(BufFile *file)
}
/*
* Enforce per-file size limit only for temp files, else just try to
* write as much as asked...
* Determine how much we need to write into this file.
*/
bytestowrite = file->nbytes - wpos;
availbytes = MAX_PHYSICAL_FILESIZE - file->curOffset;
@ -471,8 +451,8 @@ BufFileFlush(BufFile *file)
* BufFileSeek
*
* Like fseek(), except that target position needs two values in order to
* work when logical filesize exceeds maximum value representable by long.
* We do not support relative seeks across more than LONG_MAX, however.
* work when logical filesize exceeds maximum value representable by off_t.
* We do not support relative seeks across more than that, however.
*
* Result is 0 if OK, EOF if not. Logical position is not moved if an
* impossible seek is attempted.

2
src/include/storage/buffile.h
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@ -1,7 +1,7 @@
/*-------------------------------------------------------------------------
*
* buffile.h
* Management of large buffered files, primarily temporary files.
* Management of large buffered temporary files.
*
* The BufFile routines provide a partial replacement for stdio atop
* virtual file descriptors managed by fd.c. Currently they only support