relpath.h

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/*-------------------------------------------------------------------------
 *
 * relpath.h
 *      Declarations for GetRelationPath() and friends
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/common/relpath.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef RELPATH_H
#define RELPATH_H
 
/*
 *  Required here; note that CppAsString2() does not throw an error if the
 *  symbol is not defined.
 */
#include "catalog/catversion.h"
 
/*
 * RelFileNumber data type identifies the specific relation file name.
 */
typedef Oid RelFileNumber;
#define InvalidRelFileNumber        ((RelFileNumber) InvalidOid)
#define RelFileNumberIsValid(relnumber) \
                ((bool) ((relnumber) != InvalidRelFileNumber))
 
/*
 * Name of major-version-specific tablespace subdirectories
 */
#define TABLESPACE_VERSION_DIRECTORY    "PG_" PG_MAJORVERSION "_" \
                                    CppAsString2(CATALOG_VERSION_NO)
 
/*
 * Tablespace path (relative to installation's $PGDATA).
 *
 * These values should not be changed as many tools rely on it.
 */
#define PG_TBLSPC_DIR "pg_tblspc"
#define PG_TBLSPC_DIR_SLASH "pg_tblspc/"    /* required for strings
                                             * comparisons */
 
/* Characters to allow for an OID in a relation path */
#define OIDCHARS        10      /* max chars printed by %u */
 
/*
 * Stuff for fork names.
 *
 * The physical storage of a relation consists of one or more forks.
 * The main fork is always created, but in addition to that there can be
 * additional forks for storing various metadata. ForkNumber is used when
 * we need to refer to a specific fork in a relation.
 */
typedef enum ForkNumber
{
    InvalidForkNumber = -1,
    MAIN_FORKNUM = 0,
    FSM_FORKNUM,
    VISIBILITYMAP_FORKNUM,
    INIT_FORKNUM,
 
    /*
     * NOTE: if you add a new fork, change MAX_FORKNUM and possibly
     * FORKNAMECHARS below, and update the forkNames array in
     * src/common/relpath.c
     */
} ForkNumber;
 
#define MAX_FORKNUM     INIT_FORKNUM
 
#define FORKNAMECHARS   4       /* max chars for a fork name */
 
extern PGDLLIMPORT const char *const forkNames[];
 
extern ForkNumber forkname_to_number(const char *forkName);
extern int  forkname_chars(const char *str, ForkNumber *fork);
 
 
/*
 * Unfortunately, there's no easy way to derive PROCNUMBER_CHARS from
 * MAX_BACKENDS. MAX_BACKENDS is 2^18-1. Crosschecked in test_relpath().
 */
#define PROCNUMBER_CHARS    6
 
/*
 * The longest possible relation path lengths is from the following format:
 * sprintf(rp.path, "%s/%u/%s/%u/t%d_%u",
 *         PG_TBLSPC_DIR, spcOid,
 *         TABLESPACE_VERSION_DIRECTORY,
 *         dbOid, procNumber, relNumber);
 *
 * Note this does *not* include the trailing null-byte, to make it easier to
 * combine it with other lengths.
 */
#define REL_PATH_STR_MAXLEN \
    ( \
        sizeof(PG_TBLSPC_DIR) - 1 \
        + sizeof((char)'/') \
        + OIDCHARS /* spcOid */ \
        + sizeof((char)'/') \
        + sizeof(TABLESPACE_VERSION_DIRECTORY) - 1 \
        + sizeof((char)'/') \
        + OIDCHARS /* dbOid */ \
        + sizeof((char)'/') \
        + sizeof((char)'t') /* temporary table indicator */ \
        + PROCNUMBER_CHARS /* procNumber */ \
        + sizeof((char)'_') \
        + OIDCHARS /* relNumber */ \
        + sizeof((char)'_') \
        + FORKNAMECHARS /* forkNames[forkNumber] */ \
    )
 
/*
 * String of the exact length required to represent a relation path. We return
 * this struct, instead of char[REL_PATH_STR_MAXLEN + 1], as the pointer would
 * decay to a plain char * too easily, possibly preventing the compiler from
 * detecting invalid references to the on-stack return value of
 * GetRelationPath().
 */
typedef struct RelPathStr
{
    char        str[REL_PATH_STR_MAXLEN + 1];
} RelPathStr;
 
 
/*
 * Stuff for computing filesystem pathnames for relations.
 */
extern char *GetDatabasePath(Oid dbOid, Oid spcOid);
 
extern RelPathStr GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
                                  int procNumber, ForkNumber forkNumber);
 
/*
 * Wrapper macros for GetRelationPath.  Beware of multiple
 * evaluation of the RelFileLocator or RelFileLocatorBackend argument!
 */
 
/* First argument is a RelFileLocator */
#define relpathbackend(rlocator, backend, forknum) \
    GetRelationPath((rlocator).dbOid, (rlocator).spcOid, (rlocator).relNumber, \
                    backend, forknum)
 
/* First argument is a RelFileLocator */
#define relpathperm(rlocator, forknum) \
    relpathbackend(rlocator, INVALID_PROC_NUMBER, forknum)
 
/* First argument is a RelFileLocatorBackend */
#define relpath(rlocator, forknum) \
    relpathbackend((rlocator).locator, (rlocator).backend, forknum)
 
#endif                          /* RELPATH_H */