/*-------------------------------------------------------------------------

 *

 * fileset.c

 *    Management of named temporary files.

 *

 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group

 * Portions Copyright (c) 1994, Regents of the University of California

 *

 * IDENTIFICATION

 *    src/backend/storage/file/fileset.c

 *

 * FileSets provide a temporary namespace (think directory) so that files can

 * be discovered by name.

 *

 * FileSets can be used by backends when the temporary files need to be

 * opened/closed multiple times and the underlying files need to survive across

 * transactions.

 *

 *-------------------------------------------------------------------------

 */

#include "postgres.h"

#include <limits.h>

#include "commands/tablespace.h"

#include "common/file_utils.h"

#include "common/hashfn.h"

#include "miscadmin.h"

#include "storage/fileset.h"

static void FileSetPath(char *path, FileSet *fileset, Oid tablespace);

static void FilePath(char *path, FileSet *fileset, const char *name);

static Oid  ChooseTablespace(const FileSet *fileset, const char *name);

/*

 * Initialize a space for temporary files. This API can be used by shared

 * fileset as well as if the temporary files are used only by single backend

 * but the files need to be opened and closed multiple times and also the

 * underlying files need to survive across transactions.

 *

 * The callers are expected to explicitly remove such files by using

 * FileSetDelete/FileSetDeleteAll.

 *

 * Files will be distributed over the tablespaces configured in

 * temp_tablespaces.

 *

 * Under the covers the set is one or more directories which will eventually

 * be deleted.

 */

void

FileSetInit(FileSet *fileset)

{

  static uint32 counter = 0;

  fileset->creator_pid = MyProcPid;

  fileset->number = counter;

  counter = (counter + 1) % INT_MAX;

  /* Capture the tablespace OIDs so that all backends agree on them. */

  PrepareTempTablespaces();

  fileset->ntablespaces =

    GetTempTablespaces(&fileset->tablespaces[0],

               lengthof(fileset->tablespaces));

  if (fileset->ntablespaces == 0)

  {

    /* If the GUC is empty, use current database's default tablespace */

    fileset->tablespaces[0] = MyDatabaseTableSpace;

    fileset->ntablespaces = 1;

  }

  else

  {

    int     i;

    /*

     * An entry of InvalidOid means use the default tablespace for the

     * current database.  Replace that now, to be sure that all users of

     * the FileSet agree on what to do.

     */

    for (i = 0; i < fileset->ntablespaces; i++)

    {

      if (fileset->tablespaces[i] == InvalidOid)

        fileset->tablespaces[i] = MyDatabaseTableSpace;

    }

  }

}

/*

 * Create a new file in the given set.

 */

File

FileSetCreate(FileSet *fileset, const char *name)

{

  char    path[MAXPGPATH];

  File    file;

  FilePath(path, fileset, name);

  file = PathNameCreateTemporaryFile(path, false);

  /* If we failed, see if we need to create the directory on demand. */

  if (file <= 0)

  {

    char    tempdirpath[MAXPGPATH];

    char    filesetpath[MAXPGPATH];

    Oid     tablespace = ChooseTablespace(fileset, name);

    TempTablespacePath(tempdirpath, tablespace);

    FileSetPath(filesetpath, fileset, tablespace);

    PathNameCreateTemporaryDir(tempdirpath, filesetpath);

    file = PathNameCreateTemporaryFile(path, true);

  }

  return file;

}

/*

 * Open a file that was created with FileSetCreate()

 */

File

FileSetOpen(FileSet *fileset, const char *name, int mode)

{

  char    path[MAXPGPATH];

  File    file;

  FilePath(path, fileset, name);

  file = PathNameOpenTemporaryFile(path, mode);

  return file;

}

/*

 * Delete a file that was created with FileSetCreate().

 *

 * Return true if the file existed, false if didn't.

 */

bool

FileSetDelete(FileSet *fileset, const char *name,

        bool error_on_failure)

{

  char    path[MAXPGPATH];

  FilePath(path, fileset, name);

  return PathNameDeleteTemporaryFile(path, error_on_failure);

}

/*

 * Delete all files in the set.

 */

void

FileSetDeleteAll(FileSet *fileset)

{

  char    dirpath[MAXPGPATH];

  int     i;

  /*

   * Delete the directory we created in each tablespace.  Doesn't fail

   * because we use this in error cleanup paths, but can generate LOG

   * message on IO error.

   */

  for (i = 0; i < fileset->ntablespaces; ++i)

  {

    FileSetPath(dirpath, fileset, fileset->tablespaces[i]);

    PathNameDeleteTemporaryDir(dirpath);

  }

}

/*

 * Build the path for the directory holding the files backing a FileSet in a

 * given tablespace.

 */

static void

FileSetPath(char *path, FileSet *fileset, Oid tablespace)

{

  char    tempdirpath[MAXPGPATH];

  TempTablespacePath(tempdirpath, tablespace);

  snprintf(path, MAXPGPATH, "%s/%s%lu.%u.fileset",

       tempdirpath, PG_TEMP_FILE_PREFIX,

       (unsigned long) fileset->creator_pid, fileset->number);

}

/*

 * Sorting has to determine which tablespace a given temporary file belongs in.

 */

static Oid

ChooseTablespace(const FileSet *fileset, const char *name)

{

  uint32    hash = hash_bytes((const unsigned char *) name, strlen(name));

  return fileset->tablespaces[hash % fileset->ntablespaces];

}

/*

 * Compute the full path of a file in a FileSet.

 */

static void

FilePath(char *path, FileSet *fileset, const char *name)

{

  char    dirpath[MAXPGPATH];

  FileSetPath(dirpath, fileset, ChooseTablespace(fileset, name));

  snprintf(path, MAXPGPATH, "%s/%s", dirpath, name);

}