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Diffstat (limited to 'innobase/btr/btr0btr.c')
| -rw-r--r-- | innobase/btr/btr0btr.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/innobase/btr/btr0btr.c b/innobase/btr/btr0btr.c index 38d97785832..7a7678b2dcf 100644 --- a/innobase/btr/btr0btr.c +++ b/innobase/btr/btr0btr.c @@ -22,6 +22,25 @@ Created 6/2/1994 Heikki Tuuri #include "ibuf0ibuf.h" /* +Latching strategy of the InnoDB B-tree +-------------------------------------- +A tree latch protects all non-leaf nodes of the tree. Each node of a tree +also has a latch of its own. + +A B-tree operation normally first acquires an S-latch on the tree. It +searches down the tree and releases the tree latch when it has the +leaf node latch. To save CPU time we do not acquire any latch on +non-leaf nodes of the tree during a search, those pages are only bufferfixed. + +If an operation needs to restructure the tree, it acquires an X-latch on +the tree before searching to a leaf node. If it needs, for example, to +split a leaf, +(1) InnoDB decides the split point in the leaf, +(2) allocates a new page, +(3) inserts the appropriate node pointer to the first non-leaf level, +(4) releases the tree X-latch, +(5) and then moves records from the leaf to the new allocated page. + Node pointers ------------- Leaf pages of a B-tree contain the index records stored in the |