MDEV-371 Unique Index for long columns

This patch implements engine independent unique hash index.

Usage:- Unique HASH index can be created automatically for blob/varchar/test column whose key
 length > handler->max_key_length()
or it can be explicitly specified.

  Automatic Creation:-
   Create TABLE t1 (a blob unique);
  Explicit Creation:-
   Create TABLE t1 (a int , unique(a) using HASH);

Internal KEY_PART Representations:-
 Long unique key_info will have 2 representations.
 (lets understand this with an example create table t1(a blob, b blob , unique(a, b)); )

 1. User Given Representation:- key_info->key_part array will be similar to what user has defined.
 So in case of example it will have 2 key_parts (a, b)

 2. Storage Engine Representation:- In this case there will be only one key_part and it will point to
 HASH_FIELD. This key_part will be always after user defined key_parts.

 So:- User Given Representation          [a] [b] [hash_key_part]
                  key_info->key_part ----^
  Storage Engine Representation          [a] [b] [hash_key_part]
                  key_info->key_part ------------^

 Table->s->key_info will have User Given Representation, While table->key_info will have Storage Engine
 Representation.Representation can be changed into each other by calling re/setup_keyinfo_hash function.

Working:-

1. So when user specifies HASH_INDEX or key_length is > handler->max_key_length(), In mysql_prepare_create_table
One extra vfield is added (for each long unique key). And key_info->algorithm is set to HA_KEY_ALG_LONG_HASH.

2. In init_from_binary_frm_image values for hash_keypart is set (like fieldnr , field and flags)

3. In parse_vcol_defs, HASH_FIELD->vcol_info is created. Item_func_hash is used with list of Item_fields,
   When Explicit length is given by user then Item_left is used to concatenate Item_field values.

4. In ha_write_row/ha_update_row check_duplicate_long_entry_key is called which will create the hash key from
table->record[0] and then call ha_index_read_map , if we found duplicated hash , we will compare the result
field by field.

1 files changed, 91 insertions, 0 deletions

diff --git a/mysql-test/main/long_unique_debug.test b/mysql-test/main/long_unique_debug.test
new file mode 100644
index 00000000000..63ebfa89b48
--- /dev/null
+++ b/mysql-test/main/long_unique_debug.test
@@ -0,0 +1,91 @@
+--source include/have_debug.inc
+--source include/have_innodb.inc
+--echo #In this test case we will check what will happen in the case of hash collision
+
+SET debug_dbug="d,same_long_unique_hash";
+create table t1(a blob unique);
+
+FLUSH STATUS;
+insert into t1 values('xyz');
+insert into t1 values('abc');
+insert into t1 values('sachin');
+--error ER_DUP_ENTRY
+insert into t1 values('sachin');
+insert into t1 values('maria');
+--error ER_DUP_ENTRY
+insert into t1 values('maria');
+drop table t1;
+SHOW STATUS LIKE 'handler_read_next';
+
+SET debug_dbug="";
+create table t1(a blob unique);
+FLUSH STATUS;
+
+insert into t1 values('xyz');
+insert into t1 values('abc');
+insert into t1 values('sachin');
+--error ER_DUP_ENTRY
+insert into t1 values('sachin');
+insert into t1 values('maria');
+--error ER_DUP_ENTRY
+insert into t1 values('maria');
+drop table t1;
+SHOW STATUS LIKE 'handler_read_next';
+
+SET debug_dbug="d,same_long_unique_hash";
+create table t1(a blob unique, b blob unique);
+
+insert into t1 values('xyz', 11);
+insert into t1 values('abc', 22);
+insert into t1 values('sachin', 1);
+--error ER_DUP_ENTRY
+insert into t1 values('sachin', 4);
+insert into t1 values('maria', 2);
+--error ER_DUP_ENTRY
+insert into t1 values('maria', 3);
+drop table t1;
+
+create table t1(a blob , b blob , unique(a,b));
+
+insert into t1 values('xyz', 11);
+insert into t1 values('abc', 22);
+insert into t1 values('sachin', 1);
+--error ER_DUP_ENTRY
+insert into t1 values('sachin', 1);
+insert into t1 values('maria', 2);
+--error ER_DUP_ENTRY
+insert into t1 values('maria', 2);
+drop table t1;
+
+--echo ##Internal State of long unique tables
+SET debug_dbug="d,print_long_unique_internal_state";
+create table t1 ( a blob unique);
+SET debug_dbug="";
+drop table t1;
+
+SET debug_dbug="d,print_long_unique_internal_state";
+create table t1 ( a blob unique, b blob unique , c blob  unique);
+SET debug_dbug="";
+drop table t1;
+
+SET debug_dbug="d,print_long_unique_internal_state";
+create table t1 ( a blob , b blob , c blob , d blob , unique (a,b), unique(c, d));
+SET debug_dbug="";
+drop table t1;
+
+SET debug_dbug="d,print_long_unique_internal_state";
+create table t1(a int primary key, b blob unique , c blob unique not null);
+SET debug_dbug="";
+drop table t1;
+
+--echo ##Using hash
+SET debug_dbug="d,print_long_unique_internal_state";
+create table t1(a int ,b int , c int,  unique(a, b, c) using hash);
+SET debug_dbug="";
+drop table t1;
+
+--echo ##Using hash but with memory engine so no long unique column
+SET debug_dbug="d,print_long_unique_internal_state";
+create table t1(a int ,b int , c int,  unique(a, b, c) using hash) engine=memory;
+SET debug_dbug="";
+drop table t1;