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-rw-r--r--innobase/include/btr0pcur.h64
1 files changed, 37 insertions, 27 deletions
diff --git a/innobase/include/btr0pcur.h b/innobase/include/btr0pcur.h
index 6465093e3c1..05b55e4491d 100644
--- a/innobase/include/btr0pcur.h
+++ b/innobase/include/btr0pcur.h
@@ -19,9 +19,15 @@ Created 2/23/1996 Heikki Tuuri
#include "btr0types.h"
/* Relative positions for a stored cursor position */
-#define BTR_PCUR_ON 1
-#define BTR_PCUR_BEFORE 2
-#define BTR_PCUR_AFTER 3
+#define BTR_PCUR_ON 1
+#define BTR_PCUR_BEFORE 2
+#define BTR_PCUR_AFTER 3
+/* Note that if the tree is not empty, btr_pcur_store_position does not
+use the following, but only uses the above three alternatives, where the
+position is stored relative to a specific record: this makes implementation
+of a scroll cursor easier */
+#define BTR_PCUR_BEFORE_FIRST_IN_TREE 4 /* in an empty tree */
+#define BTR_PCUR_AFTER_LAST_IN_TREE 5 /* in an empty tree */
/******************************************************************
Allocates memory for a persistent cursor object and initializes the cursor. */
@@ -170,34 +176,16 @@ btr_pcur_close(
/******************************************************************
The position of the cursor is stored by taking an initial segment of the
record the cursor is positioned on, before, or after, and copying it to the
-cursor data structure. NOTE that the page where the cursor is positioned
-must not be empty! */
+cursor data structure, or just setting a flag if the cursor id before the
+first in an EMPTY tree, or after the last in an EMPTY tree. NOTE that the
+page where the cursor is positioned must not be empty if the index tree is
+not totally empty! */
void
btr_pcur_store_position(
/*====================*/
- btr_pcur_t* cursor, /* in: persistent cursor */
- mtr_t* mtr); /* in: mtr */
-/******************************************************************
-If the latch mode of the cursor is BTR_LEAF_SEARCH or BTR_LEAF_MODIFY,
-releases the page latch and bufferfix reserved by the cursor.
-NOTE! In the case of BTR_LEAF_MODIFY, there should not exist changes
-made by the current mini-transaction to the data protected by the
-cursor latch, as then the latch must not be released until mtr_commit. */
-
-void
-btr_pcur_release_leaf(
-/*==================*/
btr_pcur_t* cursor, /* in: persistent cursor */
mtr_t* mtr); /* in: mtr */
-/*************************************************************
-Gets the rel_pos field for a cursor whose position has been stored. */
-UNIV_INLINE
-ulint
-btr_pcur_get_rel_pos(
-/*=================*/
- /* out: BTR_PCUR_ON, ... */
- btr_pcur_t* cursor);/* in: persistent cursor */
/******************************************************************
Restores the stored position of a persistent cursor bufferfixing the page and
obtaining the specified latches. If the cursor position was saved when the
@@ -207,7 +195,9 @@ to the last record LESS OR EQUAL to the stored record;
the last record LESS than the user record which was the successor of the page
infimum;
(3) cursor was positioned on the page supremum: restores to the first record
-GREATER than the user record which was the predecessor of the supremum. */
+GREATER than the user record which was the predecessor of the supremum.
+(4) cursor was positioned before the first or after the last in an empty tree:
+restores to before first or after the last in the tree. */
ibool
btr_pcur_restore_position(
@@ -220,6 +210,26 @@ btr_pcur_restore_position(
ulint latch_mode, /* in: BTR_SEARCH_LEAF, ... */
btr_pcur_t* cursor, /* in: detached persistent cursor */
mtr_t* mtr); /* in: mtr */
+/******************************************************************
+If the latch mode of the cursor is BTR_LEAF_SEARCH or BTR_LEAF_MODIFY,
+releases the page latch and bufferfix reserved by the cursor.
+NOTE! In the case of BTR_LEAF_MODIFY, there should not exist changes
+made by the current mini-transaction to the data protected by the
+cursor latch, as then the latch must not be released until mtr_commit. */
+
+void
+btr_pcur_release_leaf(
+/*==================*/
+ btr_pcur_t* cursor, /* in: persistent cursor */
+ mtr_t* mtr); /* in: mtr */
+/*************************************************************
+Gets the rel_pos field for a cursor whose position has been stored. */
+UNIV_INLINE
+ulint
+btr_pcur_get_rel_pos(
+/*=================*/
+ /* out: BTR_PCUR_ON, ... */
+ btr_pcur_t* cursor);/* in: persistent cursor */
/*************************************************************
Sets the mtr field for a pcur. */
UNIV_INLINE
@@ -458,7 +468,7 @@ struct btr_pcur_struct{
ulint search_mode; /* PAGE_CUR_G, ... */
/*-----------------------------*/
/* NOTE that the following fields may possess dynamically allocated
- memory, which should be freed if not needed anymore! */
+ memory which should be freed if not needed anymore! */
mtr_t* mtr; /* NULL, or this field may contain
a mini-transaction which holds the