comments

storage/maria/ma_checkpoint.c

@@ -501,11 +501,6 @@ filter_flush_data_file_evenly(enum pagecache_page_type type,
 
    @note MikaelR questioned why the same thread does two different jobs, the
    risk could be that while a checkpoint happens no LRD flushing happens.
-
-   @note MikaelR noted that he observed that Linux's file cache may never
-   fsync to  disk until this cache is full, at which point it decides to empty
-   the cache, making the machine very slow. A solution was to fsync after
-   writing 2 MB.
 */
 
 pthread_handler_t ma_checkpoint_background(void *arg)
@@ -622,6 +617,13 @@ pthread_handler_t ma_checkpoint_background(void *arg)
           if (filter_param.max_pages == 0) /* bunch all flushed, sleep */
             break; /* and we will continue with the same file */
           dfile++; /* otherwise all this file is flushed, move to next file */
+          /*
+            MikaelR noted that he observed that Linux's file cache may never
+            fsync to  disk until this cache is full, at which point it decides
+            to empty the cache, making the machine very slow. A solution was
+            to fsync after writing 2 MB. So we might want to fsync() here if
+            we wrote enough pages.
+          */
         }
         filter_param.is_data_file= FALSE;
         while (kfile != kfiles_end)

storage/maria/ma_pagecache.c

@@ -3568,6 +3568,10 @@ static int flush_cached_blocks(PAGECACHE *pagecache,
                         PCBLOCK_NUMBER(pagecache, block), (ulong)block,
                         block->pins));
     DBUG_ASSERT(block->pins == 1);
+    /**
+       @todo If page is contiguous with next page to flush, group flushes in
+       one single my_pwrite().
+    */
     error= pagecache_fwrite(pagecache, file,
                             block->buffer,
                             block->hash_link->pageno,

storage/maria/ma_recovery.c

@@ -253,6 +253,11 @@ int maria_apply_log(LSN from_lsn, enum maria_apply_log_way apply,
       there was a crash during a DDL (see comment in execution of
       REDO_RENAME_TABLE ).
     */
+    /**
+       @todo RECOVERY BUG instead of this warning, whenever log becomes
+       incomplete (ALTER TABLE, CREATE SELECT) write a log record
+       LOGREC_INCOMPLETE; when seeing this record, print warning below.
+    */
     tprint(tracef, "WARNING: MySQL server currently disables log records"
            " about insertion of data by ALTER TABLE"
            " (copy_data_between_tables()), applying of log records may"

storage/maria/ma_write.c

@@ -176,8 +176,15 @@ int maria_write(MARIA_HA *info, uchar *record)
       info->cur_row.checksum;
   }
   if (share->base.auto_key)
+  {
+    /**
+       @todo RECOVERY BUG
+       if updated here, it's not recoverable (no mutex => checkpoint may see a
+       crazy value and flush it into the table's state on disk).
+    */
     set_if_bigger(info->s->state.auto_increment,
                   ma_retrieve_auto_increment(info, record));
+  }
   info->update= (HA_STATE_CHANGED | HA_STATE_AKTIV | HA_STATE_WRITTEN |
 		 HA_STATE_ROW_CHANGED);
   info->state->records+= !share->now_transactional; /*otherwise already done*/