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.
2019-02-20 02:53:08 +05:30
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--source include/have_debug.inc
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2019-02-21 22:42:00 +01:00
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#
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# MDEV-371 Unique indexes for blobs
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#
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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.
2019-02-20 02:53:08 +05:30
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--echo #In this test case we will check what will happen in the case of hash collision
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SET debug_dbug="d,same_long_unique_hash";
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create table t1(a blob unique);
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FLUSH STATUS;
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insert into t1 values('xyz');
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insert into t1 values('abc');
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insert into t1 values('sachin');
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--error ER_DUP_ENTRY
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insert into t1 values('sachin');
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insert into t1 values('maria');
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--error ER_DUP_ENTRY
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insert into t1 values('maria');
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drop table t1;
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SHOW STATUS LIKE 'handler_read_next';
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SET debug_dbug="";
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create table t1(a blob unique);
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FLUSH STATUS;
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insert into t1 values('xyz');
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insert into t1 values('abc');
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insert into t1 values('sachin');
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--error ER_DUP_ENTRY
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insert into t1 values('sachin');
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insert into t1 values('maria');
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--error ER_DUP_ENTRY
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insert into t1 values('maria');
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drop table t1;
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SHOW STATUS LIKE 'handler_read_next';
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SET debug_dbug="d,same_long_unique_hash";
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create table t1(a blob unique, b blob unique);
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insert into t1 values('xyz', 11);
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insert into t1 values('abc', 22);
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insert into t1 values('sachin', 1);
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--error ER_DUP_ENTRY
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insert into t1 values('sachin', 4);
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insert into t1 values('maria', 2);
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--error ER_DUP_ENTRY
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insert into t1 values('maria', 3);
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drop table t1;
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create table t1(a blob , b blob , unique(a,b));
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insert into t1 values('xyz', 11);
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insert into t1 values('abc', 22);
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insert into t1 values('sachin', 1);
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--error ER_DUP_ENTRY
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insert into t1 values('sachin', 1);
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insert into t1 values('maria', 2);
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--error ER_DUP_ENTRY
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insert into t1 values('maria', 2);
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drop table t1;
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--echo ##Internal State of long unique tables
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SET debug_dbug="d,print_long_unique_internal_state";
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create table t1 ( a blob unique);
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SET debug_dbug="";
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drop table t1;
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SET debug_dbug="d,print_long_unique_internal_state";
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create table t1 ( a blob unique, b blob unique , c blob unique);
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SET debug_dbug="";
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drop table t1;
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SET debug_dbug="d,print_long_unique_internal_state";
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create table t1 ( a blob , b blob , c blob , d blob , unique (a,b), unique(c, d));
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SET debug_dbug="";
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drop table t1;
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SET debug_dbug="d,print_long_unique_internal_state";
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create table t1(a int primary key, b blob unique , c blob unique not null);
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SET debug_dbug="";
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drop table t1;
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--echo ##Using hash
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SET debug_dbug="d,print_long_unique_internal_state";
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create table t1(a int ,b int , c int, unique(a, b, c) using hash);
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SET debug_dbug="";
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drop table t1;
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--echo ##Using hash but with memory engine so no long unique column
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SET debug_dbug="d,print_long_unique_internal_state";
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create table t1(a int ,b int , c int, unique(a, b, c) using hash) engine=memory;
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SET debug_dbug="";
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drop table t1;
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