597 lines
14 KiB
C
597 lines
14 KiB
C
/*-------------------------------------------------------------------------
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*
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* be-fsstubs.c
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* Builtin functions for open/close/read/write operations on large objects
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*
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* Portions Copyright (c) 1996-2006, 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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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/libpq/be-fsstubs.c,v 1.83 2006/09/07 15:37:25 momjian Exp $
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*
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* NOTES
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* This should be moved to a more appropriate place. It is here
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* for lack of a better place.
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*
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* These functions store LargeObjectDesc structs in a private MemoryContext,
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* which means that large object descriptors hang around until we destroy
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* the context at transaction end. It'd be possible to prolong the lifetime
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* of the context so that LO FDs are good across transactions (for example,
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* we could release the context only if we see that no FDs remain open).
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* But we'd need additional state in order to do the right thing at the
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* end of an aborted transaction. FDs opened during an aborted xact would
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* still need to be closed, since they might not be pointing at valid
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* relations at all. Locking semantics are also an interesting problem
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* if LOs stay open across transactions. For now, we'll stick with the
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* existing documented semantics of LO FDs: they're only good within a
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* transaction.
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*
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* As of PostgreSQL 8.0, much of the angst expressed above is no longer
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* relevant, and in fact it'd be pretty easy to allow LO FDs to stay
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* open across transactions. (Snapshot relevancy would still be an issue.)
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* However backwards compatibility suggests that we should stick to the
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* status quo.
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "libpq/be-fsstubs.h"
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#include "libpq/libpq-fs.h"
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#include "miscadmin.h"
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#include "storage/fd.h"
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#include "storage/large_object.h"
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#include "utils/memutils.h"
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/*#define FSDB 1*/
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#define BUFSIZE 8192
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/*
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* LO "FD"s are indexes into the cookies array.
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*
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* A non-null entry is a pointer to a LargeObjectDesc allocated in the
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* LO private memory context "fscxt". The cookies array itself is also
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* dynamically allocated in that context. Its current allocated size is
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* cookies_len entries, of which any unused entries will be NULL.
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*/
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static LargeObjectDesc **cookies = NULL;
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static int cookies_size = 0;
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static MemoryContext fscxt = NULL;
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#define CreateFSContext() \
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do { \
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if (fscxt == NULL) \
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fscxt = AllocSetContextCreate(TopMemoryContext, \
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"Filesystem", \
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ALLOCSET_DEFAULT_MINSIZE, \
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ALLOCSET_DEFAULT_INITSIZE, \
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ALLOCSET_DEFAULT_MAXSIZE); \
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} while (0)
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static int newLOfd(LargeObjectDesc *lobjCookie);
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static void deleteLOfd(int fd);
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/*****************************************************************************
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* File Interfaces for Large Objects
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*****************************************************************************/
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Datum
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lo_open(PG_FUNCTION_ARGS)
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{
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Oid lobjId = PG_GETARG_OID(0);
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int32 mode = PG_GETARG_INT32(1);
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LargeObjectDesc *lobjDesc;
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int fd;
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#if FSDB
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elog(DEBUG4, "lo_open(%u,%d)", lobjId, mode);
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#endif
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CreateFSContext();
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lobjDesc = inv_open(lobjId, mode, fscxt);
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if (lobjDesc == NULL)
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{ /* lookup failed */
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#if FSDB
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elog(DEBUG4, "could not open large object %u", lobjId);
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#endif
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PG_RETURN_INT32(-1);
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}
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fd = newLOfd(lobjDesc);
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PG_RETURN_INT32(fd);
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}
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Datum
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lo_close(PG_FUNCTION_ARGS)
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{
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int32 fd = PG_GETARG_INT32(0);
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if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
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{
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ereport(ERROR,
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(errcode(ERRCODE_UNDEFINED_OBJECT),
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errmsg("invalid large-object descriptor: %d", fd)));
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PG_RETURN_INT32(-1);
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}
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#if FSDB
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elog(DEBUG4, "lo_close(%d)", fd);
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#endif
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inv_close(cookies[fd]);
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deleteLOfd(fd);
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PG_RETURN_INT32(0);
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}
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/*****************************************************************************
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* Bare Read/Write operations --- these are not fmgr-callable!
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*
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* We assume the large object supports byte oriented reads and seeks so
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* that our work is easier.
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*
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*****************************************************************************/
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int
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lo_read(int fd, char *buf, int len)
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{
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int status;
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if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
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{
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ereport(ERROR,
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(errcode(ERRCODE_UNDEFINED_OBJECT),
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errmsg("invalid large-object descriptor: %d", fd)));
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return -1;
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}
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status = inv_read(cookies[fd], buf, len);
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return status;
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}
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int
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lo_write(int fd, const char *buf, int len)
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{
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int status;
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if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
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{
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ereport(ERROR,
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(errcode(ERRCODE_UNDEFINED_OBJECT),
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errmsg("invalid large-object descriptor: %d", fd)));
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return -1;
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}
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if ((cookies[fd]->flags & IFS_WRLOCK) == 0)
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ereport(ERROR,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
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errmsg("large object descriptor %d was not opened for writing",
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fd)));
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status = inv_write(cookies[fd], buf, len);
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return status;
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}
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Datum
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lo_lseek(PG_FUNCTION_ARGS)
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{
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int32 fd = PG_GETARG_INT32(0);
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int32 offset = PG_GETARG_INT32(1);
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int32 whence = PG_GETARG_INT32(2);
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int status;
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if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
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{
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ereport(ERROR,
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(errcode(ERRCODE_UNDEFINED_OBJECT),
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errmsg("invalid large-object descriptor: %d", fd)));
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PG_RETURN_INT32(-1);
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}
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status = inv_seek(cookies[fd], offset, whence);
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PG_RETURN_INT32(status);
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}
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Datum
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lo_creat(PG_FUNCTION_ARGS)
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{
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Oid lobjId;
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/*
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* We don't actually need to store into fscxt, but create it anyway to
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* ensure that AtEOXact_LargeObject knows there is state to clean up
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*/
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CreateFSContext();
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lobjId = inv_create(InvalidOid);
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PG_RETURN_OID(lobjId);
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}
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Datum
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lo_create(PG_FUNCTION_ARGS)
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{
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Oid lobjId = PG_GETARG_OID(0);
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/*
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* We don't actually need to store into fscxt, but create it anyway to
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* ensure that AtEOXact_LargeObject knows there is state to clean up
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*/
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CreateFSContext();
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lobjId = inv_create(lobjId);
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PG_RETURN_OID(lobjId);
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}
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Datum
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lo_tell(PG_FUNCTION_ARGS)
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{
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int32 fd = PG_GETARG_INT32(0);
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if (fd < 0 || fd >= cookies_size || cookies[fd] == NULL)
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{
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ereport(ERROR,
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(errcode(ERRCODE_UNDEFINED_OBJECT),
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errmsg("invalid large-object descriptor: %d", fd)));
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PG_RETURN_INT32(-1);
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}
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PG_RETURN_INT32(inv_tell(cookies[fd]));
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}
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Datum
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lo_unlink(PG_FUNCTION_ARGS)
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{
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Oid lobjId = PG_GETARG_OID(0);
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/*
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* If there are any open LO FDs referencing that ID, close 'em.
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*/
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if (fscxt != NULL)
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{
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int i;
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for (i = 0; i < cookies_size; i++)
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{
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if (cookies[i] != NULL && cookies[i]->id == lobjId)
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{
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inv_close(cookies[i]);
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deleteLOfd(i);
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}
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}
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}
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/*
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* inv_drop does not create a need for end-of-transaction cleanup and
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* hence we don't need to have created fscxt.
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*/
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PG_RETURN_INT32(inv_drop(lobjId));
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}
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/*****************************************************************************
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* Read/Write using bytea
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*****************************************************************************/
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Datum
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loread(PG_FUNCTION_ARGS)
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{
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int32 fd = PG_GETARG_INT32(0);
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int32 len = PG_GETARG_INT32(1);
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bytea *retval;
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int totalread;
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if (len < 0)
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len = 0;
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retval = (bytea *) palloc(VARHDRSZ + len);
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totalread = lo_read(fd, VARDATA(retval), len);
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VARATT_SIZEP(retval) = totalread + VARHDRSZ;
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PG_RETURN_BYTEA_P(retval);
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}
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Datum
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lowrite(PG_FUNCTION_ARGS)
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{
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int32 fd = PG_GETARG_INT32(0);
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bytea *wbuf = PG_GETARG_BYTEA_P(1);
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int bytestowrite;
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int totalwritten;
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bytestowrite = VARSIZE(wbuf) - VARHDRSZ;
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totalwritten = lo_write(fd, VARDATA(wbuf), bytestowrite);
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PG_RETURN_INT32(totalwritten);
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}
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/*****************************************************************************
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* Import/Export of Large Object
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*****************************************************************************/
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/*
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* lo_import -
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* imports a file as an (inversion) large object.
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*/
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Datum
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lo_import(PG_FUNCTION_ARGS)
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{
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text *filename = PG_GETARG_TEXT_P(0);
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File fd;
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int nbytes,
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tmp;
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char buf[BUFSIZE];
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char fnamebuf[MAXPGPATH];
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LargeObjectDesc *lobj;
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Oid lobjOid;
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#ifndef ALLOW_DANGEROUS_LO_FUNCTIONS
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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errmsg("must be superuser to use server-side lo_import()"),
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errhint("Anyone can use the client-side lo_import() provided by libpq.")));
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#endif
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CreateFSContext();
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/*
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* open the file to be read in
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*/
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nbytes = VARSIZE(filename) - VARHDRSZ;
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if (nbytes >= MAXPGPATH)
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nbytes = MAXPGPATH - 1;
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memcpy(fnamebuf, VARDATA(filename), nbytes);
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fnamebuf[nbytes] = '\0';
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fd = PathNameOpenFile(fnamebuf, O_RDONLY | PG_BINARY, 0666);
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if (fd < 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not open server file \"%s\": %m",
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fnamebuf)));
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/*
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* create an inversion object
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*/
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lobjOid = inv_create(InvalidOid);
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/*
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* read in from the filesystem and write to the inversion object
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*/
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lobj = inv_open(lobjOid, INV_WRITE, fscxt);
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while ((nbytes = FileRead(fd, buf, BUFSIZE)) > 0)
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{
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tmp = inv_write(lobj, buf, nbytes);
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Assert(tmp == nbytes);
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}
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if (nbytes < 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not read server file \"%s\": %m",
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fnamebuf)));
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inv_close(lobj);
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FileClose(fd);
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PG_RETURN_OID(lobjOid);
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}
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/*
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* lo_export -
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* exports an (inversion) large object.
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*/
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Datum
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lo_export(PG_FUNCTION_ARGS)
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{
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Oid lobjId = PG_GETARG_OID(0);
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text *filename = PG_GETARG_TEXT_P(1);
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File fd;
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int nbytes,
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tmp;
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char buf[BUFSIZE];
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char fnamebuf[MAXPGPATH];
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LargeObjectDesc *lobj;
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mode_t oumask;
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#ifndef ALLOW_DANGEROUS_LO_FUNCTIONS
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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errmsg("must be superuser to use server-side lo_export()"),
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errhint("Anyone can use the client-side lo_export() provided by libpq.")));
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#endif
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CreateFSContext();
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/*
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* open the inversion object (no need to test for failure)
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*/
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lobj = inv_open(lobjId, INV_READ, fscxt);
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/*
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* open the file to be written to
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*
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* Note: we reduce backend's normal 077 umask to the slightly friendlier
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* 022. This code used to drop it all the way to 0, but creating
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* world-writable export files doesn't seem wise.
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*/
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nbytes = VARSIZE(filename) - VARHDRSZ;
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if (nbytes >= MAXPGPATH)
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nbytes = MAXPGPATH - 1;
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memcpy(fnamebuf, VARDATA(filename), nbytes);
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fnamebuf[nbytes] = '\0';
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oumask = umask((mode_t) 0022);
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fd = PathNameOpenFile(fnamebuf, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY, 0666);
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umask(oumask);
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if (fd < 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not create server file \"%s\": %m",
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fnamebuf)));
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/*
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* read in from the inversion file and write to the filesystem
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*/
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while ((nbytes = inv_read(lobj, buf, BUFSIZE)) > 0)
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{
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tmp = FileWrite(fd, buf, nbytes);
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if (tmp != nbytes)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not write server file \"%s\": %m",
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fnamebuf)));
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}
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FileClose(fd);
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inv_close(lobj);
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PG_RETURN_INT32(1);
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}
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/*
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* AtEOXact_LargeObject -
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* prepares large objects for transaction commit
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*/
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void
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AtEOXact_LargeObject(bool isCommit)
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{
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int i;
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if (fscxt == NULL)
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return; /* no LO operations in this xact */
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/*
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* Close LO fds and clear cookies array so that LO fds are no longer good.
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* On abort we skip the close step.
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*/
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for (i = 0; i < cookies_size; i++)
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{
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if (cookies[i] != NULL)
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{
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if (isCommit)
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inv_close(cookies[i]);
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deleteLOfd(i);
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}
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}
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/* Needn't actually pfree since we're about to zap context */
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cookies = NULL;
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cookies_size = 0;
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/* Release the LO memory context to prevent permanent memory leaks. */
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MemoryContextDelete(fscxt);
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fscxt = NULL;
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/* Give inv_api.c a chance to clean up, too */
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close_lo_relation(isCommit);
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}
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/*
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* AtEOSubXact_LargeObject
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* Take care of large objects at subtransaction commit/abort
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*
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* Reassign LOs created/opened during a committing subtransaction
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* to the parent subtransaction. On abort, just close them.
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*/
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void
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AtEOSubXact_LargeObject(bool isCommit, SubTransactionId mySubid,
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SubTransactionId parentSubid)
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{
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int i;
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if (fscxt == NULL) /* no LO operations in this xact */
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return;
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for (i = 0; i < cookies_size; i++)
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{
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LargeObjectDesc *lo = cookies[i];
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if (lo != NULL && lo->subid == mySubid)
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{
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if (isCommit)
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lo->subid = parentSubid;
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else
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{
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/*
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* Make sure we do not call inv_close twice if it errors out
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* for some reason. Better a leak than a crash.
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*/
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deleteLOfd(i);
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inv_close(lo);
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}
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}
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}
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}
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/*****************************************************************************
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* Support routines for this file
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*****************************************************************************/
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static int
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newLOfd(LargeObjectDesc *lobjCookie)
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{
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int i,
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newsize;
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/* Try to find a free slot */
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for (i = 0; i < cookies_size; i++)
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{
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if (cookies[i] == NULL)
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{
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cookies[i] = lobjCookie;
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return i;
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}
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}
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/* No free slot, so make the array bigger */
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if (cookies_size <= 0)
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{
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/* First time through, arbitrarily make 64-element array */
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i = 0;
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newsize = 64;
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cookies = (LargeObjectDesc **)
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MemoryContextAllocZero(fscxt, newsize * sizeof(LargeObjectDesc *));
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cookies_size = newsize;
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}
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else
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|
{
|
|
/* Double size of array */
|
|
i = cookies_size;
|
|
newsize = cookies_size * 2;
|
|
cookies = (LargeObjectDesc **)
|
|
repalloc(cookies, newsize * sizeof(LargeObjectDesc *));
|
|
MemSet(cookies + cookies_size, 0,
|
|
(newsize - cookies_size) * sizeof(LargeObjectDesc *));
|
|
cookies_size = newsize;
|
|
}
|
|
|
|
Assert(cookies[i] == NULL);
|
|
cookies[i] = lobjCookie;
|
|
return i;
|
|
}
|
|
|
|
static void
|
|
deleteLOfd(int fd)
|
|
{
|
|
cookies[fd] = NULL;
|
|
}
|