| /*------------------------------------------------------------------------- | |
| * | |
| * large_object.h | |
| * Declarations for PostgreSQL large objects. POSTGRES 4.2 supported | |
| * zillions of large objects (internal, external, jaquith, inversion). | |
| * Now we only support inversion. | |
| * | |
| * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group | |
| * Portions Copyright (c) 1994, Regents of the University of California | |
| * | |
| * src/include/storage/large_object.h | |
| * | |
| *------------------------------------------------------------------------- | |
| */ | |
| /*---------- | |
| * Data about a currently-open large object. | |
| * | |
| * id is the logical OID of the large object | |
| * snapshot is the snapshot to use for read/write operations | |
| * subid is the subtransaction that opened the desc (or currently owns it) | |
| * offset is the current seek offset within the LO | |
| * flags contains some flag bits | |
| * | |
| * NOTE: as of v11, permission checks are made when the large object is | |
| * opened; therefore IFS_RDLOCK/IFS_WRLOCK indicate that read or write mode | |
| * has been requested *and* the corresponding permission has been checked. | |
| * | |
| * NOTE: before 7.1, we also had to store references to the separate table | |
| * and index of a specific large object. Now they all live in pg_largeobject | |
| * and are accessed via a common relation descriptor. | |
| *---------- | |
| */ | |
| typedef struct LargeObjectDesc | |
| { | |
| Oid id; /* LO's identifier */ | |
| Snapshot snapshot; /* snapshot to use */ | |
| SubTransactionId subid; /* owning subtransaction ID */ | |
| uint64 offset; /* current seek pointer */ | |
| int flags; /* see flag bits below */ | |
| /* bits in flags: */ | |
| } LargeObjectDesc; | |
| /* | |
| * Each "page" (tuple) of a large object can hold this much data | |
| * | |
| * We could set this as high as BLCKSZ less some overhead, but it seems | |
| * better to make it a smaller value, so that not as much space is used | |
| * up when a page-tuple is updated. Note that the value is deliberately | |
| * chosen large enough to trigger the tuple toaster, so that we will | |
| * attempt to compress page tuples in-line. (But they won't be moved off | |
| * unless the user creates a toast-table for pg_largeobject...) | |
| * | |
| * Also, it seems to be a smart move to make the page size be a power of 2, | |
| * since clients will often be written to send data in power-of-2 blocks. | |
| * This avoids unnecessary tuple updates caused by partial-page writes. | |
| * | |
| * NB: Changing LOBLKSIZE requires an initdb. | |
| */ | |
| /* | |
| * Maximum length in bytes for a large object. To make this larger, we'd | |
| * have to widen pg_largeobject.pageno as well as various internal variables. | |
| */ | |
| /* | |
| * GUC: backwards-compatibility flag to suppress LO permission checks | |
| */ | |
| extern PGDLLIMPORT bool lo_compat_privileges; | |
| /* | |
| * Function definitions... | |
| */ | |
| /* inversion stuff in inv_api.c */ | |
| extern void close_lo_relation(bool isCommit); | |
| extern Oid inv_create(Oid lobjId); | |
| extern LargeObjectDesc *inv_open(Oid lobjId, int flags, MemoryContext mcxt); | |
| extern void inv_close(LargeObjectDesc *obj_desc); | |
| extern int inv_drop(Oid lobjId); | |
| extern int64 inv_seek(LargeObjectDesc *obj_desc, int64 offset, int whence); | |
| extern int64 inv_tell(LargeObjectDesc *obj_desc); | |
| extern int inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes); | |
| extern int inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes); | |
| extern void inv_truncate(LargeObjectDesc *obj_desc, int64 len); | |