| /*------------------------------------------------------------------------- | |
| * | |
| * logtape.h | |
| * Management of "logical tapes" within temporary files. | |
| * | |
| * See logtape.c for explanations. | |
| * | |
| * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group | |
| * Portions Copyright (c) 1994, Regents of the University of California | |
| * | |
| * src/include/utils/logtape.h | |
| * | |
| *------------------------------------------------------------------------- | |
| */ | |
| /* | |
| * LogicalTapeSet and LogicalTape are opaque types whose details are not | |
| * known outside logtape.c. | |
| */ | |
| typedef struct LogicalTapeSet LogicalTapeSet; | |
| typedef struct LogicalTape LogicalTape; | |
| /* | |
| * The approach tuplesort.c takes to parallel external sorts is that workers, | |
| * whose state is almost the same as independent serial sorts, are made to | |
| * produce a final materialized tape of sorted output in all cases. This is | |
| * frozen, just like any case requiring a final materialized tape. However, | |
| * there is one difference, which is that freezing will also export an | |
| * underlying shared fileset BufFile for sharing. Freezing produces TapeShare | |
| * metadata for the worker when this happens, which is passed along through | |
| * shared memory to leader. | |
| * | |
| * The leader process can then pass an array of TapeShare metadata (one per | |
| * worker participant) to LogicalTapeSetCreate(), alongside a handle to a | |
| * shared fileset, which is sufficient to construct a new logical tapeset that | |
| * consists of each of the tapes materialized by workers. | |
| * | |
| * Note that while logtape.c does create an empty leader tape at the end of the | |
| * tapeset in the leader case, it can never be written to due to a restriction | |
| * in the shared buffile infrastructure. | |
| */ | |
| typedef struct TapeShare | |
| { | |
| /* | |
| * Currently, all the leader process needs is the location of the | |
| * materialized tape's first block. | |
| */ | |
| int64 firstblocknumber; | |
| } TapeShare; | |
| /* | |
| * prototypes for functions in logtape.c | |
| */ | |
| extern LogicalTapeSet *LogicalTapeSetCreate(bool preallocate, | |
| SharedFileSet *fileset, int worker); | |
| extern void LogicalTapeClose(LogicalTape *lt); | |
| extern void LogicalTapeSetClose(LogicalTapeSet *lts); | |
| extern LogicalTape *LogicalTapeCreate(LogicalTapeSet *lts); | |
| extern LogicalTape *LogicalTapeImport(LogicalTapeSet *lts, int worker, TapeShare *shared); | |
| extern void LogicalTapeSetForgetFreeSpace(LogicalTapeSet *lts); | |
| extern size_t LogicalTapeRead(LogicalTape *lt, void *ptr, size_t size); | |
| extern void LogicalTapeWrite(LogicalTape *lt, const void *ptr, size_t size); | |
| extern void LogicalTapeRewindForRead(LogicalTape *lt, size_t buffer_size); | |
| extern void LogicalTapeFreeze(LogicalTape *lt, TapeShare *share); | |
| extern size_t LogicalTapeBackspace(LogicalTape *lt, size_t size); | |
| extern void LogicalTapeSeek(LogicalTape *lt, int64 blocknum, int offset); | |
| extern void LogicalTapeTell(LogicalTape *lt, int64 *blocknum, int *offset); | |
| extern int64 LogicalTapeSetBlocks(LogicalTapeSet *lts); | |