MDEV-8827 Duplicate key with auto increment

fix innodb auto-increment handling
three bugs:
1. innobase_next_autoinc treated the case of current<offset incorrectly
2. ha_innobase::get_auto_increment didn't recalculate current when increment changed
3. ha_innobase::get_auto_increment didn't pass offset down to innobase_next_autoinc

mysql-test/suite/innodb/r/innodb-autoinc.result

@@ -567,7 +567,7 @@ Variable_name	Value
 auto_increment_increment	65535
 auto_increment_offset	65535
 INSERT INTO t1 VALUES (NULL),(NULL);
-ERROR 22003: Out of range value for column 'c1' at row 1
+ERROR HY000: Failed to read auto-increment value from storage engine
 SELECT * FROM t1;
 c1
 1
@@ -660,7 +660,7 @@ t2	CREATE TABLE `t2` (
   `n` int(10) unsigned NOT NULL,
   `o` enum('FALSE','TRUE') DEFAULT NULL,
   PRIMARY KEY (`m`)
-) ENGINE=InnoDB AUTO_INCREMENT=19 DEFAULT CHARSET=latin1
+) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=latin1
 INSERT INTO t1 (b,c) SELECT n,o FROM t2 ;
 SHOW CREATE TABLE t1;
 Table	Create Table

mysql-test/suite/innodb/t/innodb-autoinc.test

@@ -349,7 +349,7 @@ INSERT INTO t1 VALUES (18446744073709551610); #-- 2^64 - 2
 SELECT * FROM t1;
 SET @@SESSION.AUTO_INCREMENT_INCREMENT=1152921504606846976, @@SESSION.AUTO_INCREMENT_OFFSET=1152921504606846976;
 SHOW VARIABLES LIKE "%auto_inc%";
---error 167
+--error 1467
 INSERT INTO t1 VALUES (NULL),(NULL);
 SELECT * FROM t1;
 DROP TABLE t1;

storage/innobase/handler/ha_innodb.cc

@@ -1504,10 +1504,11 @@ innobase_next_autoinc(
 	if (next_value == 0) {
 		ulonglong	next;
 
-		if (current > offset) {
+		if (current >= offset) {
 			next = (current - offset) / step;
 		} else {
-			next = (offset - current) / step;
+			next = 0;
+			block -= step;
 		}
 
 		ut_a(max_value > next);
@@ -10445,15 +10446,12 @@ ha_innobase::get_auto_increment(
 
 		current = *first_value;
 
-		/* If the increment step of the auto increment column
-		decreases then it is not affecting the immediate
-		next value in the series. */
-		if (prebuilt->autoinc_increment > increment) {
+		if (prebuilt->autoinc_increment != increment) {
 
 			current = autoinc - prebuilt->autoinc_increment;
 
 			current = innobase_next_autoinc(
-				current, 1, increment, 1, col_max_value);
+				current, 1, increment, offset, col_max_value);
 
 			dict_table_autoinc_initialize(prebuilt->table, current);
 

storage/xtradb/handler/ha_innodb.cc

@@ -1748,10 +1748,11 @@ innobase_next_autoinc(
 	if (next_value == 0) {
 		ulonglong	next;
 
-		if (current > offset) {
+		if (current >= offset) {
 			next = (current - offset) / step;
 		} else {
-			next = (offset - current) / step;
+			next = 0;
+			block -= step;
 		}
 
 		ut_a(max_value > next);
@@ -11604,15 +11605,12 @@ ha_innobase::get_auto_increment(
 
 		current = *first_value;
 
-		/* If the increment step of the auto increment column
-		decreases then it is not affecting the immediate
-		next value in the series. */
-		if (prebuilt->autoinc_increment > increment) {
+		if (prebuilt->autoinc_increment != increment) {
 
 			current = autoinc - prebuilt->autoinc_increment;
 
 			current = innobase_next_autoinc(
-				current, 1, increment, 1, col_max_value);
+				current, 1, increment, offset, col_max_value);
 
 			dict_table_autoinc_initialize(prebuilt->table, current);