branches/zip: ha_innobase::prepare_drop_index(): When there is a

foreign key constraint, find a truly equivalent index for it.
If none is available, refuse to drop the index.  MySQL can drop
an index when creating a "stronger" index.

This was reported as Mantis issue #70 and MySQL Bug #38786.

innodb-index.test: Add a test case.

dict_foreign_find_equiv_index(): New function, to replace the
incorrectly written function dict_table_find_equivalent_index().

dict_table_replace_index_in_foreign_list(): Simplify the implementation.

dict/dict0dict.c

@@ -2162,6 +2162,30 @@ next_rec:
 	return(NULL);
 }
 
+/**************************************************************************
+Find an index that is equivalent to the one passed in and is not marked
+for deletion. */
+UNIV_INTERN
+dict_index_t*
+dict_foreign_find_equiv_index(
+/*==========================*/
+				/* out: index equivalent to
+				foreign->foreign_index, or NULL */
+	dict_foreign_t*	foreign)/* in: foreign key */
+{
+	ut_a(foreign != NULL);
+
+	/* Try to find an index which contains the columns as the
+	first fields and in the right order, and the types are the
+	same as in foreign->foreign_index */
+
+	return(dict_foreign_find_index(
+		       foreign->foreign_table,
+		       foreign->foreign_col_names, foreign->n_fields,
+		       foreign->foreign_index, TRUE, /* check types */
+		       FALSE/* allow columns to be NULL */));
+}
+
 /**************************************************************************
 Returns an index object by matching on the name and column names and
 if more than one index matches return the index with the max id */
@@ -4485,43 +4509,6 @@ dict_table_get_index_on_name(
 
 }
 
-/**************************************************************************
-Find an index that is equivalent to the one passed in and is not marked
-for deletion. */
-UNIV_INTERN
-dict_index_t*
-dict_table_find_equivalent_index(
-/*=============================*/
-				/* out: equivalent index, or NULL */
-	dict_table_t*	table,  /* in: table */
-	dict_index_t*	index)	/* in: index to match */
-{
-	ulint		i;
-	const char**	column_names;
-	dict_index_t*	equiv_index;
-
-	if (UT_LIST_GET_LEN(table->foreign_list) == 0) {
-
-		return(NULL);
-	}
-
-	column_names = mem_alloc(index->n_fields * sizeof *column_names);
-
-	/* Convert the column names to the format & type accepted by the find
-	index function */
-	for (i = 0; i < index->n_fields; i++) {
-		column_names[i] = index->fields[i].name;
-	}
-
-	equiv_index = dict_foreign_find_index(
-		table, column_names, index->n_fields,
-		index, TRUE, FALSE);
-
-	mem_free((void*) column_names);
-
-	return(equiv_index);
-}
-
 /**************************************************************************
 Replace the index passed in with another equivalent index in the tables
 foreign key list. */
@@ -4532,30 +4519,18 @@ dict_table_replace_index_in_foreign_list(
 	dict_table_t*	table,  /* in/out: table */
 	dict_index_t*	index)	/* in: index to be replaced */
 {
-	dict_index_t*	new_index;
-
-	new_index = dict_table_find_equivalent_index(table, index);
-
-	/* If match found */
-	if (new_index) {
-		dict_foreign_t*	foreign;
-
-		ut_a(new_index != index);
-
-		foreign = UT_LIST_GET_FIRST(table->foreign_list);
-
-		/* If the list is not empty then this should hold */
-		ut_a(foreign);
+	dict_foreign_t*	foreign;
 
-		/* Iterate over the foreign index list and replace the index
-		passed in with the new index */
-		while (foreign) {
+	for (foreign = UT_LIST_GET_FIRST(table->foreign_list);
+	     foreign;
+	     foreign = UT_LIST_GET_NEXT(foreign_list, foreign)) {
 
-			if (foreign->foreign_index == index) {
-				foreign->foreign_index = new_index;
-			}
+		if (foreign->foreign_index == index) {
+			dict_index_t*	new_index
+				= dict_foreign_find_equiv_index(foreign);
+			ut_a(new_index);
 
-			foreign = UT_LIST_GET_NEXT(foreign_list, foreign);
+			foreign->foreign_index = new_index;
 		}
 	}
 }

handler/handler0alter.cc

@@ -983,15 +983,16 @@ ha_innobase::prepare_drop_index(
 
 	if (trx->check_foreigns
 	    && thd_sql_command(user_thd) != SQLCOM_CREATE_INDEX) {
-		dict_index_t*	index
-			= dict_table_get_first_index(prebuilt->table);
+		dict_index_t*	index;
 
-		do {
+		for (index = dict_table_get_first_index(prebuilt->table);
+		     index;
+		     index = dict_table_get_next_index(index)) {
 			dict_foreign_t*	foreign;
 
 			if (!index->to_be_dropped) {
 
-				goto next_index;
+				continue;
 			}
 
 			/* Check if the index is referenced. */
@@ -1019,20 +1020,61 @@ index_needed:
 					ut_a(foreign->foreign_index == index);
 
 					/* Search for an equivalent index that
-					the foreign key contraint could use
+					the foreign key constraint could use
 					if this index were to be deleted. */
-					if (!dict_table_find_equivalent_index(
-						prebuilt->table,
-						foreign->foreign_index)) {
+					if (!dict_foreign_find_equiv_index(
+						foreign)) {
 
 						goto index_needed;
 					}
 				}
 			}
+		}
+	} else if (thd_sql_command(user_thd) == SQLCOM_CREATE_INDEX) {
+		/* This is a drop of a foreign key constraint index that
+		was created by MySQL when the constraint was added.  MySQL
+		does this when the user creates an index explicitly which
+		can be used in place of the automatically generated index. */
 
-next_index:
-			index = dict_table_get_next_index(index);
-		} while (index);
+		dict_index_t*	index;
+
+		for (index = dict_table_get_first_index(prebuilt->table);
+		     index;
+		     index = dict_table_get_next_index(index)) {
+			dict_foreign_t*	foreign;
+
+			if (!index->to_be_dropped) {
+
+				continue;
+			}
+
+			/* Check if this index references some other table */
+			foreign = dict_table_get_foreign_constraint(
+				prebuilt->table, index);
+
+			if (foreign == NULL) {
+
+				continue;
+			}
+
+			ut_a(foreign->foreign_index == index);
+
+			/* Search for an equivalent index that the
+			foreign key constraint could use if this index
+			were to be deleted. */
+
+			if (!dict_foreign_find_equiv_index(foreign)) {
+				trx_set_detailed_error(
+					trx,
+					"Index needed in foreign key "
+					"constraint");
+
+				trx->error_info = foreign->foreign_index;
+
+				err = HA_ERR_DROP_INDEX_FK;
+				break;
+			}
+		}
 	}
 
 func_exit:

include/dict0dict.h

@@ -420,6 +420,16 @@ dict_table_get_on_id_low(
 				/* out: table, NULL if does not exist */
 	dulint	table_id);	/* in: table id */
 /**************************************************************************
+Find an index that is equivalent to the one passed in and is not marked
+for deletion. */
+UNIV_INTERN
+dict_index_t*
+dict_foreign_find_equiv_index(
+/*==========================*/
+				/* out: index equivalent to
+				foreign->foreign_index, or NULL */
+	dict_foreign_t*	foreign);/* in: foreign key */
+/**************************************************************************
 Returns an index object by matching on the name and column names and if
 more than index is found return the index with the higher id.*/
 UNIV_INTERN
@@ -1085,16 +1095,6 @@ dict_table_get_index_on_name(
 	dict_table_t*	table,	/* in: table */
 	const char*	name);	/* in: name of the index to find */
 /**************************************************************************
-Find an index that is equivalent to the one passed in and is not marked
-for deletion. */
-UNIV_INTERN
-dict_index_t*
-dict_table_find_equivalent_index(
-/*=============================*/
-				/* out: equivalent index, or NULL */
-	dict_table_t*	table,  /* in: table */
-	dict_index_t*	index);	/* in: index to match */
-/**************************************************************************
 In case there is more than one index with the same name return the index
 with the min(id). */
 UNIV_INTERN

mysql-test/innodb-index.result

@@ -960,3 +960,167 @@ t1	CREATE TABLE `t1` (
   KEY `t1st` (`s`(1),`t`(1))
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 drop table t1;
+SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
+SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0;
+CREATE TABLE t1(
+c1	BIGINT(12) NOT NULL,
+PRIMARY KEY (c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+CREATE TABLE t2(
+c1	BIGINT(16) NOT NULL,
+c2	BIGINT(12) NOT NULL,
+c3	BIGINT(12) NOT NULL,
+PRIMARY KEY (c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+FOREIGN KEY (c3) REFERENCES t1(c1);
+SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
+SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`),
+  KEY `fk_t2_ca` (`c3`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+CREATE INDEX i_t2_c3_c2 ON t2(c3, c2);
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`),
+  KEY `i_t2_c3_c2` (`c3`,`c2`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
+SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;
+INSERT INTO t2 VALUES(0,0,0);
+ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`))
+INSERT INTO t1 VALUES(0);
+INSERT INTO t2 VALUES(0,0,0);
+DROP TABLE t2;
+CREATE TABLE t2(
+c1	BIGINT(16) NOT NULL,
+c2	BIGINT(12) NOT NULL,
+c3	BIGINT(12) NOT NULL,
+PRIMARY KEY (c1,c2,c3)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+FOREIGN KEY (c3) REFERENCES t1(c1);
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`,`c2`,`c3`),
+  KEY `fk_t2_ca` (`c3`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+CREATE INDEX i_t2_c3_c2 ON t2(c3, c2);
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`,`c2`,`c3`),
+  KEY `i_t2_c3_c2` (`c3`,`c2`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+INSERT INTO t2 VALUES(0,0,1);
+ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`))
+INSERT INTO t2 VALUES(0,0,0);
+DELETE FROM t1;
+ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`) REFERENCES `t1` (`c1`))
+DELETE FROM t2;
+DROP TABLE t2;
+DROP TABLE t1;
+CREATE TABLE t1(
+c1	BIGINT(12) NOT NULL,
+c2	INT(4) NOT NULL,
+PRIMARY KEY (c2,c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+CREATE TABLE t2(
+c1	BIGINT(16) NOT NULL,
+c2	BIGINT(12) NOT NULL,
+c3	BIGINT(12) NOT NULL,
+PRIMARY KEY (c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+FOREIGN KEY (c3,c2) REFERENCES t1(c1,c1);
+ERROR HY000: Can't create table '#sql-temporary' (errno: 150)
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2);
+ERROR HY000: Can't create table '#sql-temporary' (errno: 150)
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1);
+ERROR HY000: Can't create table '#sql-temporary' (errno: 150)
+ALTER TABLE t1 MODIFY COLUMN c2 BIGINT(12) NOT NULL;
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2);
+ERROR HY000: Can't create table '#sql-temporary' (errno: 150)
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1);
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c1` bigint(12) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  PRIMARY KEY (`c2`,`c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`),
+  KEY `fk_t2_ca` (`c3`,`c2`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+CREATE INDEX i_t2_c2_c1 ON t2(c2, c1);
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`),
+  KEY `fk_t2_ca` (`c3`,`c2`),
+  KEY `i_t2_c2_c1` (`c2`,`c1`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+CREATE INDEX i_t2_c3_c1_c2 ON t2(c3, c1, c2);
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`),
+  KEY `fk_t2_ca` (`c3`,`c2`),
+  KEY `i_t2_c2_c1` (`c2`,`c1`),
+  KEY `i_t2_c3_c1_c2` (`c3`,`c1`,`c2`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+CREATE INDEX i_t2_c3_c2 ON t2(c3, c2);
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` bigint(16) NOT NULL,
+  `c2` bigint(12) NOT NULL,
+  `c3` bigint(12) NOT NULL,
+  PRIMARY KEY (`c1`),
+  KEY `i_t2_c2_c1` (`c2`,`c1`),
+  KEY `i_t2_c3_c1_c2` (`c3`,`c1`,`c2`),
+  KEY `i_t2_c3_c2` (`c3`,`c2`),
+  CONSTRAINT `fk_t2_ca` FOREIGN KEY (`c3`, `c2`) REFERENCES `t1` (`c2`, `c1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+DROP TABLE t2;
+DROP TABLE t1;

mysql-test/innodb-index.test

@@ -387,3 +387,114 @@ create index t1ut on t1 (u(1), t(1));
 create index t1st on t1 (s(1), t(1));
 show create table t1;
 drop table t1;
+
+#
+# Test to check whether CREATE INDEX handles implicit foreign key
+# constraint modifications (Issue #70, Bug #38786)
+#
+SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
+SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0;
+
+CREATE TABLE t1(
+  c1	BIGINT(12) NOT NULL,
+  PRIMARY KEY (c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+
+CREATE TABLE t2(
+  c1	BIGINT(16) NOT NULL,
+  c2	BIGINT(12) NOT NULL,
+  c3	BIGINT(12) NOT NULL,
+  PRIMARY KEY (c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+ FOREIGN KEY (c3) REFERENCES t1(c1);
+
+SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
+SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;
+
+SHOW CREATE TABLE t2;
+
+CREATE INDEX i_t2_c3_c2 ON t2(c3, c2);
+
+SHOW CREATE TABLE t2;
+
+SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
+SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;
+
+--error ER_NO_REFERENCED_ROW_2
+INSERT INTO t2 VALUES(0,0,0);
+INSERT INTO t1 VALUES(0);
+INSERT INTO t2 VALUES(0,0,0);
+
+DROP TABLE t2;
+
+CREATE TABLE t2(
+  c1	BIGINT(16) NOT NULL,
+  c2	BIGINT(12) NOT NULL,
+  c3	BIGINT(12) NOT NULL,
+  PRIMARY KEY (c1,c2,c3)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+ FOREIGN KEY (c3) REFERENCES t1(c1);
+
+SHOW CREATE TABLE t2;
+
+CREATE INDEX i_t2_c3_c2 ON t2(c3, c2);
+
+SHOW CREATE TABLE t2;
+--error ER_NO_REFERENCED_ROW_2
+INSERT INTO t2 VALUES(0,0,1);
+INSERT INTO t2 VALUES(0,0,0);
+--error ER_ROW_IS_REFERENCED_2
+DELETE FROM t1;
+DELETE FROM t2;
+
+DROP TABLE t2;
+DROP TABLE t1;
+
+CREATE TABLE t1(
+  c1	BIGINT(12) NOT NULL,
+  c2	INT(4) NOT NULL,
+  PRIMARY KEY (c2,c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+
+CREATE TABLE t2(
+  c1	BIGINT(16) NOT NULL,
+  c2	BIGINT(12) NOT NULL,
+  c3	BIGINT(12) NOT NULL,
+  PRIMARY KEY (c1)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1;
+
+--replace_regex /'test\.#sql-[0-9a-f-]*_1'/'#sql-temporary'/
+--error ER_CANT_CREATE_TABLE
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+ FOREIGN KEY (c3,c2) REFERENCES t1(c1,c1);
+--replace_regex /'test\.#sql-[0-9a-f-]*_1'/'#sql-temporary'/
+--error ER_CANT_CREATE_TABLE
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+ FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2);
+--replace_regex /'test\.#sql-[0-9a-f-]*_1'/'#sql-temporary'/
+--error ER_CANT_CREATE_TABLE
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+ FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1);
+ALTER TABLE t1 MODIFY COLUMN c2 BIGINT(12) NOT NULL;
+--replace_regex /'test\.#sql-[0-9a-f-]*_1'/'#sql-temporary'/
+--error ER_CANT_CREATE_TABLE
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+ FOREIGN KEY (c3,c2) REFERENCES t1(c1,c2);
+
+ALTER TABLE t2 ADD CONSTRAINT fk_t2_ca
+ FOREIGN KEY (c3,c2) REFERENCES t1(c2,c1);
+SHOW CREATE TABLE t1;
+SHOW CREATE TABLE t2;
+CREATE INDEX i_t2_c2_c1 ON t2(c2, c1);
+SHOW CREATE TABLE t2;
+CREATE INDEX i_t2_c3_c1_c2 ON t2(c3, c1, c2);
+SHOW CREATE TABLE t2;
+CREATE INDEX i_t2_c3_c2 ON t2(c3, c2);
+SHOW CREATE TABLE t2;
+
+DROP TABLE t2;
+DROP TABLE t1;