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4f44aa04b5
kibitzing from Tom Lane. Large objects are now all stored in a single system relation "pg_largeobject" --- no more xinv or xinx files, no more relkind 'l'. This should offer substantial performance improvement for large numbers of LOs, since there won't be directory bloat anymore. It'll also fix problems like running out of locktable space when you access thousands of LOs in one transaction. Also clean up cruft in read/write routines. LOs with "holes" in them (never-written byte ranges) now work just like Unix files with holes do: a hole reads as zeroes but doesn't occupy storage space. INITDB forced!
74 lines
2.3 KiB
C
74 lines
2.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* large_object.h
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* file of info for Postgres large objects. POSTGRES 4.2 supports
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* zillions of large objects (internal, external, jaquith, inversion).
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* Now we only support inversion.
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*
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: large_object.h,v 1.18 2000/10/24 01:38:43 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef LARGE_OBJECT_H
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#define LARGE_OBJECT_H
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#include "utils/rel.h"
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/*----------
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* Data about a currently-open large object.
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*
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* id is the logical OID of the large object
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* offset is the current seek offset within the LO
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* heap_r holds an open-relation reference to pg_largeobject
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* index_r holds an open-relation reference to pg_largeobject_loid_pn_index
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*
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* NOTE: before 7.1, heap_r and index_r held references to the separate
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* table and index of a specific large object. Now they all live in one rel.
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*----------
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*/
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typedef struct LargeObjectDesc {
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Oid id;
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uint32 offset; /* current seek pointer */
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int flags; /* locking info, etc */
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/* flag bits: */
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#define IFS_RDLOCK (1 << 0)
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#define IFS_WRLOCK (1 << 1)
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Relation heap_r;
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Relation index_r;
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} LargeObjectDesc;
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/*
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* Each "page" (tuple) of a large object can hold this much data
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*
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* Calculation is max tuple size less tuple header, loid field (Oid),
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* pageno field (int32), and varlena header of data (int32). Note we
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* assume none of the fields will be NULL, hence no need for null bitmap.
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*/
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#define LOBLKSIZE (MaxTupleSize \
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- MAXALIGN(offsetof(HeapTupleHeaderData, t_bits)) \
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- sizeof(Oid) - sizeof(int32) * 2)
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/*
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* Function definitions...
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*/
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/* inversion stuff in inv_api.c */
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extern LargeObjectDesc *inv_create(int flags);
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extern LargeObjectDesc *inv_open(Oid lobjId, int flags);
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extern void inv_close(LargeObjectDesc *obj_desc);
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extern int inv_drop(Oid lobjId);
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extern int inv_seek(LargeObjectDesc *obj_desc, int offset, int whence);
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extern int inv_tell(LargeObjectDesc *obj_desc);
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extern int inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes);
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extern int inv_write(LargeObjectDesc *obj_desc, char *buf, int nbytes);
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#endif /* LARGE_OBJECT_H */
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