row0sel.c, btr0pcur.c, btr0pcur.ic, btr0pcur.h:

  Add diagnostic code to track assertion failure in ut_a(cursor->old_stored == BTR_PCUR_OLD_STORED); the failure happened in OPTIMIZE TABLE, and in 4.0.24 in some other context

innobase/btr/btr0pcur.c

@@ -14,6 +14,7 @@ Created 2/23/1996 Heikki Tuuri
 
 #include "ut0byte.h"
 #include "rem0cmp.h"
+#include "trx0trx.h"
 
 /******************************************************************
 Allocates memory for a persistent cursor object and initializes the cursor. */
@@ -203,7 +204,14 @@ btr_pcur_restore_position(
 
 	ut_a(cursor->pos_state == BTR_PCUR_WAS_POSITIONED
 			|| cursor->pos_state == BTR_PCUR_IS_POSITIONED);
-	ut_a(cursor->old_stored == BTR_PCUR_OLD_STORED);
+	if (cursor->old_stored != BTR_PCUR_OLD_STORED) {
+		ut_print_buf(stderr, (const byte*)cursor, sizeof(btr_pcur_t));
+		if (cursor->trx_if_known) {
+			trx_print(stderr, cursor->trx_if_known);
+		}
+		
+		ut_a(0);
+	}
 
 	if (cursor->rel_pos == BTR_PCUR_AFTER_LAST_IN_TREE
 	    || cursor->rel_pos == BTR_PCUR_BEFORE_FIRST_IN_TREE) {

innobase/include/btr0pcur.h

@@ -477,6 +477,10 @@ struct btr_pcur_struct{
 					BTR_PCUR_WAS_POSITIONED,
 					BTR_PCUR_NOT_POSITIONED */
 	ulint		search_mode;	/* PAGE_CUR_G, ... */
+	trx_t*		trx_if_known;	/* the transaction, if we know it;
+					otherwise this field is not defined;
+					can ONLY BE USED in error prints in
+					fatal assertion failures! */
 	/*-----------------------------*/
 	/* NOTE that the following fields may possess dynamically allocated
 	memory which should be freed if not needed anymore! */

innobase/include/btr0pcur.ic

@@ -493,6 +493,8 @@ btr_pcur_open(
 	btr_cur_search_to_nth_level(index, 0, tuple, mode, latch_mode,
 							btr_cursor, 0, mtr);
 	cursor->pos_state = BTR_PCUR_IS_POSITIONED;
+
+	cursor->trx_if_known = NULL;
 }
 
 /******************************************************************
@@ -535,6 +537,8 @@ btr_pcur_open_with_no_init(
 	cursor->pos_state = BTR_PCUR_IS_POSITIONED;
 
 	cursor->old_stored = BTR_PCUR_OLD_NOT_STORED;
+
+	cursor->trx_if_known = NULL;
 }
 
 /*********************************************************************
@@ -568,6 +572,8 @@ btr_pcur_open_at_index_side(
 	pcur->pos_state = BTR_PCUR_IS_POSITIONED;
 
 	pcur->old_stored = BTR_PCUR_OLD_NOT_STORED;
+
+	pcur->trx_if_known = NULL;
 }
 
 /**************************************************************************
@@ -592,6 +598,8 @@ btr_pcur_open_at_rnd_pos(
 					btr_pcur_get_btr_cur(cursor), mtr);
 	cursor->pos_state = BTR_PCUR_IS_POSITIONED;
 	cursor->old_stored = BTR_PCUR_OLD_NOT_STORED;
+
+	cursor->trx_if_known = NULL;
 }
 	
 /******************************************************************
@@ -617,4 +625,6 @@ btr_pcur_close(
 	
 	cursor->latch_mode = BTR_NO_LATCHES;
 	cursor->pos_state = BTR_PCUR_NOT_POSITIONED;
+
+	cursor->trx_if_known = NULL;
 }

innobase/row/row0sel.c

@@ -2507,6 +2507,8 @@ row_sel_get_clust_rec_for_mysql(
 
 	clust_rec = btr_pcur_get_rec(prebuilt->clust_pcur);
 
+	prebuilt->clust_pcur->trx_if_known = trx;
+
 	/* Note: only if the search ends up on a non-infimum record is the
 	low_match value the real match to the search tuple */
 
@@ -3222,6 +3224,8 @@ row_search_for_mysql(
 		btr_pcur_open_with_no_init(index, search_tuple, mode,
 					BTR_SEARCH_LEAF,
 					pcur, 0, &mtr);
+
+		pcur->trx_if_known = trx;
 	} else {
 		if (mode == PAGE_CUR_G) {
 			btr_pcur_open_at_index_side(TRUE, index,