List:Commits« Previous MessageNext Message »
From:Tatjana Azundris Nuernberg Date:February 21 2012 11:42am
Subject:bzr push into mysql-5.1 branch (tatjana.nuernberg:3691 to 3692) Bug#35396
View as plain text  
 3692 Tatjana Azundris Nuernberg	2012-02-19
      If a query's end time is before before its start time, the system clock has been turn back
      (daylight savings time etc.). When the system clock is changed, we can't tell for certain a
      given query was actually slow. We did not protect against logging such a query with a bogus
      execution time (resulting from end_time - start_time being negative), and possibly logging it
      even though it did not really take long to run.
      We now have a sanity check in place.
     @ sql/
        Make sure end time is not before start time - otherwise, we can be SURE the system clock
        was changed in between, but not by how much. In other words, when the clock is changed,
        we don't know how long a query ran, and whether it was slow.

 3691 Marko Mäkelä	2012-02-17
      This bug was originally filed and fixed as Bug#12612184. The original
      fix was buggy, and it was patched by Bug#12704861. Also that patch was
      buggy (potentially breaking crash recovery), and both fixes were
      This fix was not ported to the built-in InnoDB of MySQL 5.1, because
      the function signatures of many core functions are different from
      InnoDB Plugin and later versions. The block allocation routines and
      their callers would have to changed so that they handle block
      descriptors instead of page frames.
      When a record is updated so that its size grows, non-updated columns
      can be selected for external (off-page) storage. The bug is that the
      initially inserted updated record contains an all-zero BLOB pointer to
      the field that was not updated. Only after the BLOB pages have been
      allocated and written, the valid pointer can be written to the record.
      Between the release of the page latch in mtr_commit(mtr) after
      btr_cur_pessimistic_update() and the re-latching of the page in
      btr_pcur_restore_position(), other threads can see the invalid BLOB
      pointer consisting of 20 zero bytes. Moreover, if the system crashes
      at this point, the situation could persist after crash recovery, and
      the contents of the non-updated column would be permanently lost.
      The problem is amplified by the ROW_FORMAT=DYNAMIC and
      ROW_FORMAT=COMPRESSED that were introduced in
      innodb_file_format=barracuda in InnoDB Plugin, but the bug does exist
      in all InnoDB versions.
      The fix is as follows. After a pessimistic B-tree operation that needs
      to write out off-page columns, allocate the pages for these columns in
      the mini-transaction that performed the B-tree operation (btr_mtr),
      but write the pages in a separate mini-transaction (blob_mtr). Do
      mtr_commit(blob_mtr) before mtr_commit(btr_mtr). A quirk: Do not reuse
      pages that were previously freed in btr_mtr. Only write the off-page
      columns to 'fresh' pages.
      In this way, crash recovery will see redo log entries for blob_mtr
      before any redo log entry for btr_mtr. It will apply the BLOB page
      writes to pages that were marked free at that point. If crash recovery
      fails to see all of the btr_mtr redo log, there will be some
      unreachable BLOB data in free pages, but the B-tree will be in a
      consistent state.
      btr_page_alloc_low(): Renamed from btr_page_alloc(). Add the parameter
      init_mtr. Return an allocated block, or NULL. If init_mtr!=mtr but
      the page was already X-latched in mtr, do not initialize the page.
      btr_page_alloc(): Wrapper for btr_page_alloc_for_ibuf() and
      btr_page_free(): Add a debug assertion that the page was a B-tree page.
      btr_lift_page_up(): Return the father block.
      btr_compress(), btr_cur_compress_if_useful(): Add the parameter ibool
      adjust, for adjusting the cursor position.
      btr_cur_pessimistic_update(): Preserve the cursor position when
      big_rec will be written and the new flag BTR_KEEP_POS_FLAG is defined.
      Remove a duplicate rec_get_offsets() call. Keep the X-latch on
      index->lock when big_rec is needed.
      btr_store_big_rec_extern_fields(): Replace update_inplace with
      an operation code, and local_mtr with btr_mtr. When not doing a
      fresh insert and btr_mtr has freed pages, put aside any pages that
      were previously X-latched in btr_mtr, and free the pages after
      writing out all data. The data must be written to 'fresh' pages,
      because btr_mtr will be committed and written to the redo log after
      the BLOB writes have been written to the redo log.
      btr_blob_op_is_update(): Check if an operation passed to
      btr_store_big_rec_extern_fields() is an update or insert-by-update.
      fseg_alloc_free_page_low(), fsp_alloc_free_page(),
      fseg_alloc_free_extent(), fseg_alloc_free_page_general(): Add the
      parameter init_mtr. Return an allocated block, or NULL. If
      init_mtr!=mtr but the page was already X-latched in mtr, do not
      initialize the page.
      xdes_get_descriptor_with_space_hdr(): Assert that the file space
      header is being X-latched.
      fsp_alloc_from_free_frag(): Refactored from fsp_alloc_free_page().
      fsp_page_create(): New function, for allocating, X-latching and
      potentially initializing a page. If init_mtr!=mtr but the page was
      already X-latched in mtr, do not initialize the page.
      fsp_free_page(): Add ut_ad(0) to the error outcomes.
      fsp_free_page(), fseg_free_page_low(): Increment mtr->n_freed_pages.
      fsp_alloc_seg_inode_page(), fseg_create_general(): Assert that the
      page was not previously X-latched in the mini-transaction. A file
      segment or inode page should never be allocated in the middle of an
      mini-transaction that frees pages, such as btr_cur_pessimistic_delete().
      fseg_alloc_free_page_low(): If the hinted page was allocated, skip the
      check if the tablespace should be extended. Return NULL instead of
      FIL_NULL on failure. Remove the flag frag_page_allocated. Instead,
      return directly, because the page would already have been initialized.
      fseg_find_free_frag_page_slot() would return ULINT_UNDEFINED on error,
      not FIL_NULL. Correct a bogus assertion.
      fseg_alloc_free_page(): Redefine as a wrapper macro around
      buf_block_buf_fix_inc(): Move the definition from the buf0buf.ic to
      buf0buf.h, so that it can be called from other modules.
      mtr_t: Add n_freed_pages (number of pages that have been freed).
      page_rec_get_nth_const(), page_rec_get_nth(): The inverse function of
      page_rec_get_n_recs_before(), get the nth record of the record
      list. This is faster than iterating the linked list. Refactored from
      trx_undo_rec_copy(): Add a debug assertion for the length.
      trx_undo_add_page(): Return a block descriptor or NULL instead of a
      page number or FIL_NULL.
      trx_undo_report_row_operation(): Add debug assertions.
      trx_sys_create_doublewrite_buf(): Assert that each page was not
      previously X-latched.
      page_cur_insert_rec_zip_reorg(): Make use of page_rec_get_nth().
      row_ins_clust_index_entry_by_modify(): Pass BTR_KEEP_POS_FLAG, so that
      the repositioning of the cursor can be avoided.
      row_ins_index_entry_low(): Add DEBUG_SYNC points before and after
      writing off-page columns. If inserting by updating a delete-marked
      record, do not reposition the cursor or commit the mini-transaction
      before writing the off-page columns.
      row_build(): Tighten a debug assertion about null BLOB pointers.
      row_upd_clust_rec(): Add DEBUG_SYNC points before and after writing
      off-page columns. Do not reposition the cursor or commit the
      mini-transaction before writing the off-page columns.
      rb:939 approved by Jimmy Yang

=== modified file 'sql/'
--- a/sql/	2011-10-19 02:21:31 +0000
+++ b/sql/	2012-02-19 03:18:49 +0000
@@ -1734,8 +1734,9 @@ void log_slow_statement(THD *thd)
     ulonglong end_utime_of_query= thd->current_utime();
     thd_proc_info(thd, "logging slow query");
-    if (((end_utime_of_query - thd->utime_after_lock) >
-         thd->variables.long_query_time ||
+    if ((((end_utime_of_query > thd->utime_after_lock) &&
+          ((end_utime_of_query - thd->utime_after_lock) >
+           thd->variables.long_query_time)) ||
          ((thd->server_status &
           opt_log_queries_not_using_indexes &&

No bundle (reason: useless for push emails).
bzr push into mysql-5.1 branch (tatjana.nuernberg:3691 to 3692) Bug#35396Tatjana Azundris Nuernberg22 Feb