codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * large_object.h4 *	  Declarations for PostgreSQL large objects.  POSTGRES 4.2 supported5 *	  zillions of large objects (internal, external, jaquith, inversion).6 *	  Now we only support inversion.7 *8 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group9 * Portions Copyright (c) 1994, Regents of the University of California10 *11 * src/include/storage/large_object.h12 *13 *-------------------------------------------------------------------------14 */15#ifndef LARGE_OBJECT_H16#define LARGE_OBJECT_H17 18#include "utils/snapshot.h"19 20 21/*----------22 * Data about a currently-open large object.23 *24 * id is the logical OID of the large object25 * snapshot is the snapshot to use for read/write operations26 * subid is the subtransaction that opened the desc (or currently owns it)27 * offset is the current seek offset within the LO28 * flags contains some flag bits29 *30 * NOTE: as of v11, permission checks are made when the large object is31 * opened; therefore IFS_RDLOCK/IFS_WRLOCK indicate that read or write mode32 * has been requested *and* the corresponding permission has been checked.33 *34 * NOTE: before 7.1, we also had to store references to the separate table35 * and index of a specific large object.  Now they all live in pg_largeobject36 * and are accessed via a common relation descriptor.37 *----------38 */39typedef struct LargeObjectDesc40{41	Oid			id;				/* LO's identifier */42	Snapshot	snapshot;		/* snapshot to use */43	SubTransactionId subid;		/* owning subtransaction ID */44	uint64		offset;			/* current seek pointer */45	int			flags;			/* see flag bits below */46 47/* bits in flags: */48#define IFS_RDLOCK		(1 << 0)	/* LO was opened for reading */49#define IFS_WRLOCK		(1 << 1)	/* LO was opened for writing */50 51} LargeObjectDesc;52 53 54/*55 * Each "page" (tuple) of a large object can hold this much data56 *57 * We could set this as high as BLCKSZ less some overhead, but it seems58 * better to make it a smaller value, so that not as much space is used59 * up when a page-tuple is updated.  Note that the value is deliberately60 * chosen large enough to trigger the tuple toaster, so that we will61 * attempt to compress page tuples in-line.  (But they won't be moved off62 * unless the user creates a toast-table for pg_largeobject...)63 *64 * Also, it seems to be a smart move to make the page size be a power of 2,65 * since clients will often be written to send data in power-of-2 blocks.66 * This avoids unnecessary tuple updates caused by partial-page writes.67 *68 * NB: Changing LOBLKSIZE requires an initdb.69 */70#define LOBLKSIZE		(BLCKSZ / 4)71 72/*73 * Maximum length in bytes for a large object.  To make this larger, we'd74 * have to widen pg_largeobject.pageno as well as various internal variables.75 */76#define MAX_LARGE_OBJECT_SIZE	((int64) INT_MAX * LOBLKSIZE)77 78 79/*80 * GUC: backwards-compatibility flag to suppress LO permission checks81 */82extern PGDLLIMPORT bool lo_compat_privileges;83 84/*85 * Function definitions...86 */87 88/* inversion stuff in inv_api.c */89extern void close_lo_relation(bool isCommit);90extern Oid	inv_create(Oid lobjId);91extern LargeObjectDesc *inv_open(Oid lobjId, int flags, MemoryContext mcxt);92extern void inv_close(LargeObjectDesc *obj_desc);93extern int	inv_drop(Oid lobjId);94extern int64 inv_seek(LargeObjectDesc *obj_desc, int64 offset, int whence);95extern int64 inv_tell(LargeObjectDesc *obj_desc);96extern int	inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes);97extern int	inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes);98extern void inv_truncate(LargeObjectDesc *obj_desc, int64 len);99 100#endif							/* LARGE_OBJECT_H */101