删除老的临时文件。当postmaster主进程运行到该函数时，当前数据目录下肯定没有其他POSTGRES进程运行，所以删除老的临时文件是安全的。

RemovePgTempFiles函数删除之前postmaster session留下的临时文件和临时relation文件。该函数在Postmaster启动时调用，强制删除由OpenTemporaryFile创建的留存的文件和mdcreate创建的留存的临时relation文件。
删除pg_default tablespace下的临时文件：

  • ​​$PGDATA/base/pgsql_tmp​​
  • ​​$PGDATA/base/database_oid(目录)/t<digits>_<digits>​​
  • ​​$PGDATA/base/database_oid(目录)/t<digits>_<digits>_<forkname>​​

删除非default tablespace下的临时文件：

  • ​​pg_tblspc/目录名dname/PG_PG_MAJORVERSION_201909212/pgsql_tmp​​
  • ​​pg_tblspc/目录名dname/PG_PG_MAJORVERSION_201909212//database_oid(目录)/t<digits>_<digits>​​
  • ​​pg_tblspc/目录名dname/PG_PG_MAJORVERSION_201909212//database_oid(目录)/t<digits>_<digits>_<forkname>​​
void RemovePgTempFiles(void) {
  char    temp_path[MAXPGPATH + 10 + sizeof(TABLESPACE_VERSION_DIRECTORY) + sizeof(PG_TEMP_FILES_DIR)];
  DIR       *spc_dir;
  struct dirent *spc_de;

  /* First process temp files in pg_default ($PGDATA/base) */
  snprintf(temp_path, sizeof(temp_path), "base/%s", PG_TEMP_FILES_DIR);
  RemovePgTempFilesInDir(temp_path, true, false);
  RemovePgTempRelationFiles("base");
  
  /* Cycle through temp directories for all non-default tablespaces. */
  spc_dir = AllocateDir("pg_tblspc");
  while ((spc_de = ReadDirExtended(spc_dir, "pg_tblspc", LOG)) != NULL){
    if (strcmp(spc_de->d_name, ".") == 0 || strcmp(spc_de->d_name, "..") == 0) continue;
    snprintf(temp_path, sizeof(temp_path), "pg_tblspc/%s/%s/%s", spc_de->d_name, TABLESPACE_VERSION_DIRECTORY, PG_TEMP_FILES_DIR);
    RemovePgTempFilesInDir(temp_path, true, false);
    snprintf(temp_path, sizeof(temp_path), "pg_tblspc/%s/%s", spc_de->d_name, TABLESPACE_VERSION_DIRECTORY);
    RemovePgTempRelationFiles(temp_path);
  }
  FreeDir(spc_dir);

  /* In EXEC_BACKEND case there is a pgsql_tmp directory at the top level of DataDir as well. */
#ifdef EXEC_BACKEND
  RemovePgTempFilesInDir(PG_TEMP_FILES_DIR, true, false);
#endif
}