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445e31bdc7
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
78 lines
2.9 KiB
C
78 lines
2.9 KiB
C
/*-------------------------------------------------------------------------
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*
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* logtape.h
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* Management of "logical tapes" within temporary files.
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*
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* See logtape.c for explanations.
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*
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* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/logtape.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef LOGTAPE_H
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#define LOGTAPE_H
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#include "storage/sharedfileset.h"
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/* LogicalTapeSet is an opaque type whose details are not known outside logtape.c. */
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typedef struct LogicalTapeSet LogicalTapeSet;
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/*
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* The approach tuplesort.c takes to parallel external sorts is that workers,
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* whose state is almost the same as independent serial sorts, are made to
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* produce a final materialized tape of sorted output in all cases. This is
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* frozen, just like any case requiring a final materialized tape. However,
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* there is one difference, which is that freezing will also export an
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* underlying shared fileset BufFile for sharing. Freezing produces TapeShare
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* metadata for the worker when this happens, which is passed along through
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* shared memory to leader.
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*
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* The leader process can then pass an array of TapeShare metadata (one per
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* worker participant) to LogicalTapeSetCreate(), alongside a handle to a
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* shared fileset, which is sufficient to construct a new logical tapeset that
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* consists of each of the tapes materialized by workers.
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*
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* Note that while logtape.c does create an empty leader tape at the end of the
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* tapeset in the leader case, it can never be written to due to a restriction
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* in the shared buffile infrastructure.
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*/
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typedef struct TapeShare
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{
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/*
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* Currently, all the leader process needs is the location of the
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* materialized tape's first block.
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*/
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long firstblocknumber;
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} TapeShare;
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/*
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* prototypes for functions in logtape.c
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*/
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extern LogicalTapeSet *LogicalTapeSetCreate(int ntapes, TapeShare *shared,
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SharedFileSet *fileset, int worker);
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extern void LogicalTapeSetClose(LogicalTapeSet *lts);
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extern void LogicalTapeSetForgetFreeSpace(LogicalTapeSet *lts);
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extern size_t LogicalTapeRead(LogicalTapeSet *lts, int tapenum,
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void *ptr, size_t size);
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extern void LogicalTapeWrite(LogicalTapeSet *lts, int tapenum,
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void *ptr, size_t size);
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extern void LogicalTapeRewindForRead(LogicalTapeSet *lts, int tapenum,
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size_t buffer_size);
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extern void LogicalTapeRewindForWrite(LogicalTapeSet *lts, int tapenum);
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extern void LogicalTapeFreeze(LogicalTapeSet *lts, int tapenum,
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TapeShare *share);
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extern size_t LogicalTapeBackspace(LogicalTapeSet *lts, int tapenum,
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size_t size);
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extern void LogicalTapeSeek(LogicalTapeSet *lts, int tapenum,
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long blocknum, int offset);
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extern void LogicalTapeTell(LogicalTapeSet *lts, int tapenum,
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long *blocknum, int *offset);
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extern long LogicalTapeSetBlocks(LogicalTapeSet *lts);
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#endif /* LOGTAPE_H */
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