Fix some sloppiness in the new BufFileSize() and BufFileAppend() functions.

hlinnaka · hlinnaka · commit 445e31bdc749 · 2018-05-02T17:23:13.000+03:00
There were three related issues: * BufFileAppend() incorrectly reset the seek position on the 'source' file. As a result, if you had called BufFileRead() on the file before calling BufFileAppend(), it got confused, and subsequent calls would read/write at wrong position. * BufFileSize() did not work with files opened with BufFileOpenShared(). * FileGetSize() only worked on temporary files. To fix, change the way BufFileSize() works so that it works on shared files. Remove FileGetSize() altogether, as it's no longer needed. Remove buffilesize from TapeShare struct, as the leader process can simply call BufFileSize() to get the tape's size, there's no need to pass it through shared memory anymore. Discussion: https://www.postgresql.org/message-id/CAH2-WznEDYe_NZXxmnOfsoV54oFkTdMy7YLE2NPBLuttO96vTQ@mail.gmail.com
diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c
@@ -802,14 +802,24 @@ BufFileTellBlock(BufFile *file)
 #endif
 
 /*
- * Return the current file size.  Counts any holes left behind by
- * BufFileViewAppend as part of the size.
+ * Return the current file size.
+ *
+ * Counts any holes left behind by BufFileAppend as part of the size.
+ * Returns -1 on error.
  */
 off_t
 BufFileSize(BufFile *file)
 {
+	off_t		lastFileSize;
+
+	/* Get the size of the last physical file by seeking to end. */
+	lastFileSize = FileSeek(file->files[file->numFiles - 1], 0, SEEK_END);
+	if (lastFileSize < 0)
+		return -1;
+	file->offsets[file->numFiles - 1] = lastFileSize;
+
 	return ((file->numFiles - 1) * (off_t) MAX_PHYSICAL_FILESIZE) +
-		FileGetSize(file->files[file->numFiles - 1]);
+		lastFileSize;
 }
 
 /*
@@ -853,7 +863,7 @@ BufFileAppend(BufFile *target, BufFile *source)
 	for (i = target->numFiles; i < newNumFiles; i++)
 	{
 		target->files[i] = source->files[i - target->numFiles];
-		target->offsets[i] = 0L;
+		target->offsets[i] = source->offsets[i - target->numFiles];
 	}
 	target->numFiles = newNumFiles;
 
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
@@ -2255,16 +2255,6 @@ FileGetRawMode(File file)
 	return VfdCache[file].fileMode;
 }
 
-/*
- * FileGetSize - returns the size of file
- */
-off_t
-FileGetSize(File file)
-{
-	Assert(FileIsValid(file));
-	return VfdCache[file].fileSize;
-}
-
 /*
  * Make room for another allocatedDescs[] array entry if needed and possible.
  * Returns true if an array element is available.
diff --git a/src/backend/utils/sort/logtape.c b/src/backend/utils/sort/logtape.c
@@ -426,11 +426,17 @@ ltsConcatWorkerTapes(LogicalTapeSet *lts, TapeShare *shared,
 	{
 		char		filename[MAXPGPATH];
 		BufFile    *file;
+		off_t		filesize;
 
 		lt = &lts->tapes[i];
 
 		pg_itoa(i, filename);
 		file = BufFileOpenShared(fileset, filename);
+		filesize = BufFileSize(file);
+		if (filesize < 0)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not determine size of temporary file \"%s\"", filename)));
 
 		/*
 		 * Stash first BufFile, and concatenate subsequent BufFiles to that.
@@ -447,8 +453,8 @@ ltsConcatWorkerTapes(LogicalTapeSet *lts, TapeShare *shared,
 			lt->offsetBlockNumber = BufFileAppend(lts->pfile, file);
 		}
 		/* Don't allocate more for read buffer than could possibly help */
-		lt->max_size = Min(MaxAllocSize, shared[i].buffilesize);
-		tapeblocks = shared[i].buffilesize / BLCKSZ;
+		lt->max_size = Min(MaxAllocSize, filesize);
+		tapeblocks = filesize / BLCKSZ;
 		nphysicalblocks += tapeblocks;
 	}
 
@@ -938,7 +944,6 @@ LogicalTapeFreeze(LogicalTapeSet *lts, int tapenum, TapeShare *share)
 	{
 		BufFileExportShared(lts->pfile);
 		share->firstblocknumber = lt->firstBlockNumber;
-		share->buffilesize = BufFileSize(lts->pfile);
 	}
 }
 
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
@@ -4395,7 +4395,6 @@ tuplesort_initialize_shared(Sharedsort *shared, int nWorkers, dsm_segment *seg)
 	for (i = 0; i < nWorkers; i++)
 	{
 		shared->tapes[i].firstblocknumber = 0L;
-		shared->tapes[i].buffilesize = 0;
 	}
 }
 
diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h
@@ -78,7 +78,6 @@ extern char *FilePathName(File file);
 extern int	FileGetRawDesc(File file);
 extern int	FileGetRawFlags(File file);
 extern mode_t FileGetRawMode(File file);
-extern off_t FileGetSize(File file);
 
 /* Operations used for sharing named temporary files */
 extern File PathNameCreateTemporaryFile(const char *name, bool error_on_failure);
diff --git a/src/include/utils/logtape.h b/src/include/utils/logtape.h
@@ -44,13 +44,10 @@ typedef struct LogicalTapeSet LogicalTapeSet;
 typedef struct TapeShare
 {
 	/*
-	 * firstblocknumber is first block that should be read from materialized
-	 * tape.
-	 *
-	 * buffilesize is the size of associated BufFile following freezing.
+	 * Currently, all the leader process needs is the location of the
+	 * materialized tape's first block.
 	 */
 	long		firstblocknumber;
-	off_t		buffilesize;
 } TapeShare;
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -426,11 +426,17 @@ ltsConcatWorkerTapes(LogicalTapeSet lts, TapeShare shared,`
`426`	`426`	`{`
`427`	`427`	`char filename[MAXPGPATH];`
`428`	`428`	`BufFile *file;`
	`429`	`+ off_t filesize;`
`429`	`430`
`430`	`431`	`lt = &lts->tapes[i];`
`431`	`432`
`432`	`433`	`pg_itoa(i, filename);`
`433`	`434`	`file = BufFileOpenShared(fileset, filename);`
	`435`	`+ filesize = BufFileSize(file);`
	`436`	`+ if (filesize < 0)`
	`437`	`+ ereport(ERROR,`
	`438`	`+ (errcode_for_file_access(),`
	`439`	`+ errmsg("could not determine size of temporary file \"%s\"", filename)));`
`434`	`440`
`435`	`441`	`/*`
`436`	`442`	`* Stash first BufFile, and concatenate subsequent BufFiles to that.`
`@@ -447,8 +453,8 @@ ltsConcatWorkerTapes(LogicalTapeSet lts, TapeShare shared,`
`447`	`453`	`lt->offsetBlockNumber = BufFileAppend(lts->pfile, file);`
`448`	`454`	`}`
`449`	`455`	`/* Don't allocate more for read buffer than could possibly help */`
`450`		`- lt->max_size = Min(MaxAllocSize, shared[i].buffilesize);`
`451`		`- tapeblocks = shared[i].buffilesize / BLCKSZ;`
	`456`	`+ lt->max_size = Min(MaxAllocSize, filesize);`
	`457`	`+ tapeblocks = filesize / BLCKSZ;`
`452`	`458`	`nphysicalblocks += tapeblocks;`
`453`	`459`	`}`
`454`	`460`
`@@ -938,7 +944,6 @@ LogicalTapeFreeze(LogicalTapeSet lts, int tapenum, TapeShare share)`
`938`	`944`	`{`
`939`	`945`	`BufFileExportShared(lts->pfile);`
`940`	`946`	`share->firstblocknumber = lt->firstBlockNumber;`
`941`		`- share->buffilesize = BufFileSize(lts->pfile);`
`942`	`947`	`}`
`943`	`948`	`}`
`944`	`949`
Original file line number	Diff line number	Diff line change
`@@ -4395,7 +4395,6 @@ tuplesort_initialize_shared(Sharedsort shared, int nWorkers, dsm_segment seg)`
`4395`	`4395`	`for (i = 0; i < nWorkers; i++)`
`4396`	`4396`	`{`
`4397`	`4397`	`shared->tapes[i].firstblocknumber = 0L;`
`4398`		`- shared->tapes[i].buffilesize = 0;`
`4399`	`4398`	`}`
`4400`	`4399`	`}`
`4401`	`4400`