diff options
Diffstat (limited to 'src/backend/storage/file/fd.c')
| -rw-r--r-- | src/backend/storage/file/fd.c | 38 |
1 files changed, 37 insertions, 1 deletions
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c index f67ab94fd52..b91946a0350 100644 --- a/src/backend/storage/file/fd.c +++ b/src/backend/storage/file/fd.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.146 2009/01/01 17:23:47 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.147 2009/01/12 05:10:44 tgl Exp $ * * NOTES: * @@ -1029,6 +1029,42 @@ FileClose(File file) FreeVfd(file); } +/* + * FilePrefetch - initiate asynchronous read of a given range of the file. + * The logical seek position is unaffected. + * + * Currently the only implementation of this function is using posix_fadvise + * which is the simplest standardized interface that accomplishes this. + * We could add an implementation using libaio in the future; but note that + * this API is inappropriate for libaio, which wants to have a buffer provided + * to read into. + */ +int +FilePrefetch(File file, off_t offset, int amount) +{ +#if defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_WILLNEED) + int returnCode; + + Assert(FileIsValid(file)); + + DO_DB(elog(LOG, "FilePrefetch: %d (%s) " INT64_FORMAT " %d", + file, VfdCache[file].fileName, + (int64) offset, amount)); + + returnCode = FileAccess(file); + if (returnCode < 0) + return returnCode; + + returnCode = posix_fadvise(VfdCache[file].fd, offset, amount, + POSIX_FADV_WILLNEED); + + return returnCode; +#else + Assert(FileIsValid(file)); + return 0; +#endif +} + int FileRead(File file, char *buffer, int amount) { |