btr0btr.c Add more documentation about B-tree latching

ha_innodb.cc	Remove gaps in auto-inc in multi-row inserts, more space for foreign key listings in SHOW TABLE STATUS, move resetting of active_trx to amore logical place
dict0dict.h	Remove gaps from auto-inc sequence if errors in multi-row insert
dict0dict.c	Remove gaps from auto-inc sequence if errors in multi-row insert

3 files changed, 28 insertions, 22 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
diff --git a/innobase/dict/dict0dict.c b/innobase/dict/dict0dict.c
index 85199b90a5a..7bf85557cde 100644
--- a/innobase/dict/dict0dict.c
+++ b/innobase/dict/dict0dict.c
@@ -308,29 +308,18 @@ dict_table_autoinc_get(
 }
 
 /************************************************************************
-Reads the autoinc counter value, 0 if not yet initialized. Does not
-increment the counter. */
+Decrements the autoinc counter value by 1. */
 
-ib_longlong
-dict_table_autoinc_read(
-/*====================*/
-				/* out: value of the counter */
+void
+dict_table_autoinc_decrement(
+/*=========================*/
 	dict_table_t*	table)	/* in: table */
 {
-	ib_longlong	value;
-
 	mutex_enter(&(table->autoinc_mutex));
 
-	if (!table->autoinc_inited) {
-
-		value = 0;
-	} else {
-		value = table->autoinc;
-	}
+	table->autoinc = table->autoinc - 1;
 	
 	mutex_exit(&(table->autoinc_mutex));
-
-	return(value);
 }
 
 /************************************************************************
diff --git a/innobase/include/dict0dict.h b/innobase/include/dict0dict.h
index 832654d2666..bf393210763 100644
--- a/innobase/include/dict0dict.h
+++ b/innobase/include/dict0dict.h
@@ -114,13 +114,11 @@ dict_table_autoinc_get(
 				/* out: value for a new row, or 0 */
 	dict_table_t*	table);	/* in: table */
 /************************************************************************
-Reads the autoinc counter value, 0 if not yet initialized. Does not
-increment the counter. */
+Decrements the autoinc counter value by 1. */
 
-ib_longlong
-dict_table_autoinc_read(
-/*====================*/
-				/* out: value of the counter */
+void
+dict_table_autoinc_decrement(
+/*=========================*/
 	dict_table_t*	table);	/* in: table */
 /************************************************************************
 Peeks the autoinc counter value, 0 if not yet initialized. Does not