mirror of
https://github.com/MariaDB/server.git
synced 2025-01-30 18:41:56 +01:00
d00f19e832
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.
|
||
|---|---|---|
| .. | ||
| mysql-test/mtr2 | ||
| _check.c | ||
| _rectest.c | ||
| ChangeLog | ||
| CMakeLists.txt | ||
| ha_heap.cc | ||
| ha_heap.h | ||
| heapdef.h | ||
| hp_block.c | ||
| hp_clear.c | ||
| hp_close.c | ||
| hp_create.c | ||
| hp_delete.c | ||
| hp_extra.c | ||
| hp_hash.c | ||
| hp_info.c | ||
| hp_open.c | ||
| hp_panic.c | ||
| hp_rename.c | ||
| hp_rfirst.c | ||
| hp_rkey.c | ||
| hp_rlast.c | ||
| hp_rnext.c | ||
| hp_rprev.c | ||
| hp_rrnd.c | ||
| hp_rsame.c | ||
| hp_scan.c | ||
| hp_static.c | ||
| hp_test1.c | ||
| hp_test2.c | ||
| hp_update.c | ||
| hp_write.c | ||