Bug #20358: InnoDB hang on the adaptive hash index latch in btr0sea.c

Add --skip-innodb-adaptive-hash-index option, which is a way to
work around the bug (by disabling the adaptive hash feature entirely).

This may be useful even once the bug is fixed, for benchmarking purposes.
There are some workloads for which the adaptive hash index is not effective.

sql/ha_innodb.cc

@@ -174,6 +174,7 @@ my_bool	innobase_file_per_table			= FALSE;
 my_bool innobase_locks_unsafe_for_binlog        = FALSE;
 my_bool innobase_rollback_on_timeout		= FALSE;
 my_bool innobase_create_status_file		= FALSE;
+my_bool innobase_adaptive_hash_index		= TRUE;
 
 static char *internal_innobase_data_file_path	= NULL;
 
@@ -1376,6 +1377,8 @@ innobase_init(void)
 	srv_use_doublewrite_buf = (ibool) innobase_use_doublewrite;
 	srv_use_checksums = (ibool) innobase_use_checksums;
 
+	srv_use_adaptive_hash_indexes = (ibool) innobase_adaptive_hash_index;
+
 	os_use_large_pages = (ibool) innobase_use_large_pages;
 	os_large_page_size = (ulint) innobase_large_page_size;
 

sql/ha_innodb.h

@@ -217,7 +217,8 @@ extern my_bool innobase_log_archive,
                innobase_use_native_aio,
 	       innobase_file_per_table, innobase_locks_unsafe_for_binlog,
 	       innobase_rollback_on_timeout,
-               innobase_create_status_file;
+               innobase_create_status_file,
+               innobase_adaptive_hash_index;
 extern my_bool innobase_very_fast_shutdown; /* set this to 1 just before
 					    calling innobase_end() if you want
 					    InnoDB to shut down without

sql/mysqld.cc

@@ -4829,7 +4829,8 @@ enum options_mysqld
   OPT_MERGE,
   OPT_INNODB_ROLLBACK_ON_TIMEOUT,
   OPT_SECURE_FILE_PRIV,
-  OPT_KEEP_FILES_ON_CREATE
+  OPT_KEEP_FILES_ON_CREATE,
+  OPT_INNODB_ADAPTIVE_HASH_INDEX
 };
 
 
@@ -5057,6 +5058,12 @@ Disable with --skip-innodb-checksums.", (gptr*) &innobase_use_checksums,
    "The common part for InnoDB table spaces.", (gptr*) &innobase_data_home_dir,
    (gptr*) &innobase_data_home_dir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0,
    0},
+  {"innodb_adaptive_hash_index", OPT_INNODB_ADAPTIVE_HASH_INDEX,
+   "Enable InnoDB adaptive hash index (enabled by default).  "
+   "Disable with --skip-innodb-adaptive-hash-index.",
+   (gptr*) &innobase_adaptive_hash_index,
+   (gptr*) &innobase_adaptive_hash_index,
+   0, GET_BOOL, NO_ARG, 1, 0, 0, 0, 0, 0},
   {"innodb_doublewrite", OPT_INNODB_DOUBLEWRITE, "Enable InnoDB doublewrite buffer (enabled by default). \
 Disable with --skip-innodb-doublewrite.", (gptr*) &innobase_use_doublewrite,
    (gptr*) &innobase_use_doublewrite, 0, GET_BOOL, NO_ARG, 1, 0, 0, 0, 0, 0},

sql/set_var.cc

@@ -901,6 +901,7 @@ struct show_var_st init_vars[]= {
   {sys_innodb_concurrency_tickets.name, (char*) &sys_innodb_concurrency_tickets, SHOW_SYS},
   {"innodb_data_file_path", (char*) &innobase_data_file_path,	    SHOW_CHAR_PTR},
   {"innodb_data_home_dir",  (char*) &innobase_data_home_dir,	    SHOW_CHAR_PTR},
+  {"innodb_adaptive_hash_index", (char*) &innobase_adaptive_hash_index, SHOW_MY_BOOL},
   {"innodb_doublewrite", (char*) &innobase_use_doublewrite, SHOW_MY_BOOL},
   {sys_innodb_fast_shutdown.name,(char*) &sys_innodb_fast_shutdown, SHOW_SYS},
   {"innodb_file_io_threads", (char*) &innobase_file_io_threads, SHOW_LONG },