Bug#16208542 DROP INDEX ON A FOREIGN KEY COLUMN LEADS TO MISSING TABLE

== Analysis ==
The bug is caused by the reason that dict_load_foreigns() will return error 
when it couldn't find a equivalent fk index, and dict_load_table() who get 
the error will return NULL to indicate there is something wrong with the 
table. This happens no matter which value(1/0) is set to FOREIGN_KEY_CHECKS.

== Solution ==
Allow user to open the table with missing fk indexes when 
FOREIGN_KEY_CHECKS=0. When the table is opened, user has to recreate 
the missing indexes to fulfill the fk constraints. After that the table 
can be open in a normal way.

A new enum type in dict_err_ignore_t called DICT_ERR_IGNORE_FK_NOKEY 
is defined, with which dict_load_foreigns() will always load all the 
fk constraints and fk indexes ignoring those missing. User can decide 
which indexes should be created according to the table definition with 
all the fk constraints.

An error message can be found when open a table with missing fk indexes. 
I think using ib_logf in dict_load_table() to print the error message is 
an easy way.

rb#2308 is approved by Marko

storage/innobase/dict/dict0dict.cc

@@ -3218,11 +3218,16 @@ UNIV_INTERN
 dberr_t
 dict_foreign_add_to_cache(
 /*======================*/
-	dict_foreign_t*	foreign,	/*!< in, own: foreign key constraint */
-	const char**	col_names,	/*!< in: column names, or NULL to use
-					foreign->foreign_table->col_names */
-	bool		check_charsets)	/*!< in: whether to check charset
-					compatibility */
+	dict_foreign_t*		foreign,
+				/*!< in, own: foreign key constraint */
+	const char**		col_names,
+				/*!< in: column names, or NULL to use
+				foreign->foreign_table->col_names */
+	bool			check_charsets,
+				/*!< in: whether to check charset
+				compatibility */
+	dict_err_ignore_t	ignore_err)
+				/*!< in: error to be ignored */
 {
 	dict_table_t*	for_table;
 	dict_table_t*	ref_table;
@@ -3262,7 +3267,8 @@ dict_foreign_add_to_cache(
 			for_in_cache->n_fields, for_in_cache->foreign_index,
 			check_charsets, false);
 
-		if (index == NULL) {
+		if (index == NULL
+		    && !(ignore_err & DICT_ERR_IGNORE_FK_NOKEY)) {
 			dict_foreign_error_report(
 				ef, for_in_cache,
 				"there is no index in referenced table"
@@ -3297,7 +3303,8 @@ dict_foreign_add_to_cache(
 			& (DICT_FOREIGN_ON_DELETE_SET_NULL
 			   | DICT_FOREIGN_ON_UPDATE_SET_NULL));
 
-		if (index == NULL) {
+		if (index == NULL
+		    && !(ignore_err & DICT_ERR_IGNORE_FK_NOKEY)) {
 			dict_foreign_error_report(
 				ef, for_in_cache,
 				"there is no index in the table"

storage/innobase/dict/dict0load.cc

@@ -1,6 +1,6 @@
 /*****************************************************************************
 
-Copyright (c) 1996, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 1996, 2013, Oracle and/or its affiliates. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -2411,9 +2411,16 @@ dict_load_table(
 	if (!cached || table->ibd_file_missing) {
 		/* Don't attempt to load the indexes from disk. */
 	} else if (err == DB_SUCCESS) {
-		err = dict_load_foreigns(table->name, NULL, true, true);
+		err = dict_load_foreigns(table->name, NULL, true, true,
+					 ignore_err);
 
 		if (err != DB_SUCCESS) {
+			ib_logf(IB_LOG_LEVEL_WARN,
+				"Load table '%s' failed, the table has missing "
+				"foreign key indexes. Turn off "
+				"'foreign_key_checks' and try again.",
+				table->name);
+
 			dict_table_remove_from_cache(table);
 			table = NULL;
 		} else {
@@ -2714,18 +2721,21 @@ static __attribute__((nonnull(1), warn_unused_result))
 dberr_t
 dict_load_foreign(
 /*==============*/
-	const char*	id,	/*!< in: foreign constraint id, must be
+	const char*		id,
+				/*!< in: foreign constraint id, must be
 				'\0'-terminated */
-	const char**	col_names,
+	const char**		col_names,
 				/*!< in: column names, or NULL
 				to use foreign->foreign_table->col_names */
-	bool		check_recursive,
+	bool			check_recursive,
 				/*!< in: whether to record the foreign table
 				parent count to avoid unlimited recursive
 				load of chained foreign tables */
-	bool		check_charsets)
+	bool			check_charsets,
 				/*!< in: whether to check charset
 				compatibility */
+	dict_err_ignore_t	ignore_err)
+				/*!< in: error to be ignored */
 {
 	dict_foreign_t*	foreign;
 	dict_table_t*	sys_foreign;
@@ -2894,7 +2904,8 @@ dict_load_foreign(
 	a new foreign key constraint but loading one from the data
 	dictionary. */
 
-	return(dict_foreign_add_to_cache(foreign, col_names, check_charsets));
+	return(dict_foreign_add_to_cache(foreign, col_names, check_charsets,
+					 ignore_err));
 }
 
 /***********************************************************************//**
@@ -2908,13 +2919,15 @@ UNIV_INTERN
 dberr_t
 dict_load_foreigns(
 /*===============*/
-	const char*	table_name,	/*!< in: table name */
-	const char**	col_names,	/*!< in: column names, or NULL to use
-					table->col_names */
-	bool		check_recursive,/*!< in: Whether to check recursive
-					load of tables chained by FK */
-	bool		check_charsets)	/*!< in: whether to check charset
-					compatibility */
+	const char*		table_name,	/*!< in: table name */
+	const char**		col_names,	/*!< in: column names, or NULL
+						to use table->col_names */
+	bool			check_recursive,/*!< in: Whether to check
+						recursive load of tables
+						chained by FK */
+	bool			check_charsets,	/*!< in: whether to check
+						charset compatibility */
+	dict_err_ignore_t	ignore_err)	/*!< in: error to be ignored */
 {
 	ulint		tuple_buf[(DTUPLE_EST_ALLOC(1) + sizeof(ulint) - 1)
 				/ sizeof(ulint)];
@@ -3026,7 +3039,7 @@ dict_load_foreigns(
 	/* Load the foreign constraint definition to the dictionary cache */
 
 	err = dict_load_foreign(fk_id, col_names,
-				check_recursive, check_charsets);
+				check_recursive, check_charsets, ignore_err);
 
 	if (err != DB_SUCCESS) {
 		btr_pcur_close(&pcur);

storage/innobase/handler/ha_innodb.cc

@@ -4602,17 +4602,18 @@ UNIV_INTERN
 int
 ha_innobase::open(
 /*==============*/
-	const char*	name,		/*!< in: table name */
-	int		mode,		/*!< in: not used */
-	uint		test_if_locked)	/*!< in: not used */
-{
-	dict_table_t*	ib_table;
-	char		norm_name[FN_REFLEN];
-	THD*		thd;
-	ulint		retries = 0;
-	char*		is_part = NULL;
-	ibool		par_case_name_set = FALSE;
-	char		par_case_name[FN_REFLEN];
+	const char*		name,		/*!< in: table name */
+	int			mode,		/*!< in: not used */
+	uint			test_if_locked)	/*!< in: not used */
+{
+	dict_table_t*		ib_table;
+	char			norm_name[FN_REFLEN];
+	THD*			thd;
+	ulint			retries = 0;
+	char*			is_part = NULL;
+	ibool			par_case_name_set = FALSE;
+	char			par_case_name[FN_REFLEN];
+	dict_err_ignore_t	ignore_err = DICT_ERR_IGNORE_NONE;
 
 	DBUG_ENTER("ha_innobase::open");
 
@@ -4652,10 +4653,16 @@ ha_innobase::open(
 	is_part = strstr(norm_name, "#P#");
 #endif /* __WIN__ */
 
+	/* Check whether FOREIGN_KEY_CHECKS is set to 0. If so, the table
+	can be opened even if some FK indexes are missing. If not, the table
+	can't be opened in the same situation */
+	if (thd_test_options(thd, OPTION_NO_FOREIGN_KEY_CHECKS)) {
+		ignore_err = DICT_ERR_IGNORE_FK_NOKEY;
+	}
+
 retry:
 	/* Get pointer to a table object in InnoDB dictionary cache */
-	ib_table = dict_table_open_on_name(norm_name, FALSE, TRUE,
-					   DICT_ERR_IGNORE_NONE);
+	ib_table = dict_table_open_on_name(norm_name, FALSE, TRUE, ignore_err);
 
 	if (ib_table
 	    && ((!DICT_TF2_FLAG_IS_SET(ib_table, DICT_TF2_FTS_HAS_DOC_ID)
@@ -4721,7 +4728,7 @@ ha_innobase::open(
 
 				ib_table = dict_table_open_on_name(
 					par_case_name, FALSE, TRUE,
-					DICT_ERR_IGNORE_NONE);
+					ignore_err);
 			}
 
 			if (!ib_table) {

storage/innobase/handler/handler0alter.cc

@@ -4678,7 +4678,8 @@ innobase_update_foreign_cache(
 	and prevent the table from being evicted from the data
 	dictionary cache (work around the lack of WL#6049). */
 	DBUG_RETURN(dict_load_foreigns(user_table->name,
-				       ctx->col_names, false, true));
+				       ctx->col_names, false, true,
+				       DICT_ERR_IGNORE_NONE));
 }
 
 /** Commit the changes made during prepare_inplace_alter_table()

storage/innobase/include/dict0dict.h

@@ -1,6 +1,6 @@
 /*****************************************************************************
 
-Copyright (c) 1996, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 1996, 2013, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
 
 This program is free software; you can redistribute it and/or modify it under
@@ -408,11 +408,16 @@ UNIV_INTERN
 dberr_t
 dict_foreign_add_to_cache(
 /*======================*/
-	dict_foreign_t*	foreign,	/*!< in, own: foreign key constraint */
-	const char**	col_names,	/*!< in: column names, or NULL to use
-					foreign->foreign_table->col_names */
-	bool		check_charsets)	/*!< in: whether to check charset
-					compatibility */
+	dict_foreign_t*		foreign,
+				/*!< in, own: foreign key constraint */
+	const char**		col_names,
+				/*!< in: column names, or NULL to use
+				foreign->foreign_table->col_names */
+	bool			check_charsets,
+				/*!< in: whether to check charset
+				compatibility */
+	dict_err_ignore_t	ignore_err)
+				/*!< in: error to be ignored */
 	__attribute__((nonnull(1), warn_unused_result));
 /*********************************************************************//**
 Check if the index is referenced by a foreign key, if TRUE return the

storage/innobase/include/dict0load.h

@@ -1,6 +1,6 @@
 /*****************************************************************************
 
-Copyright (c) 1996, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 1996, 2013, Oracle and/or its affiliates. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -220,13 +220,15 @@ UNIV_INTERN
 dberr_t
 dict_load_foreigns(
 /*===============*/
-	const char*	table_name,	/*!< in: table name */
-	const char**	col_names,	/*!< in: column names, or NULL to use
-					table->col_names */
-	bool		check_recursive,/*!< in: Whether to check recursive
-					load of tables chained by FK */
-	bool		check_charsets)	/*!< in: whether to check charset
-					compatibility */
+	const char*		table_name,	/*!< in: table name */
+	const char**		col_names,	/*!< in: column names, or NULL
+						to use table->col_names */
+	bool			check_recursive,/*!< in: Whether to check
+						recursive load of tables
+						chained by FK */
+	bool			check_charsets,	/*!< in: whether to check
+						charset compatibility */
+	dict_err_ignore_t	ignore_err)	/*!< in: error to be ignored */
 	__attribute__((nonnull(1), warn_unused_result));
 /********************************************************************//**
 Prints to the standard output information on all tables found in the data

storage/innobase/include/dict0types.h

@@ -1,6 +1,6 @@
 /*****************************************************************************
 
-Copyright (c) 1996, 2011, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 1996, 2013, Oracle and/or its affiliates. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -57,6 +57,8 @@ enum dict_err_ignore_t {
 	DICT_ERR_IGNORE_INDEX_ROOT = 1,	/*!< ignore error if index root
 					page is FIL_NULL or incorrect value */
 	DICT_ERR_IGNORE_CORRUPT = 2,	/*!< skip corrupted indexes */
+	DICT_ERR_IGNORE_FK_NOKEY = 4,	/*!< ignore error if any foreign
+					key is missing */
 	DICT_ERR_IGNORE_ALL = 0xFFFF	/*!< ignore all errors */
 };
 

storage/innobase/include/handler0alter.h

@@ -1,6 +1,6 @@
 /*****************************************************************************
 
-Copyright (c) 2005, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2005, 2013, Oracle and/or its affiliates. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software

storage/innobase/row/row0mysql.cc

@@ -2521,7 +2521,8 @@ row_table_add_foreign_constraints(
 
 	if (err == DB_SUCCESS) {
 		/* Check that also referencing constraints are ok */
-		err = dict_load_foreigns(name, NULL, false, true);
+		err = dict_load_foreigns(name, NULL, false, true,
+					 DICT_ERR_IGNORE_NONE);
 	}
 
 	if (err != DB_SUCCESS) {
@@ -4986,7 +4987,8 @@ row_rename_table_for_mysql(
 
 		err = dict_load_foreigns(
 			new_name, NULL,
-			false, !old_is_tmp || trx->check_foreigns);
+			false, !old_is_tmp || trx->check_foreigns,
+			DICT_ERR_IGNORE_NONE);
 
 		if (err != DB_SUCCESS) {
 			ut_print_timestamp(stderr);