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authorSachin <sachin.setiya@mariadb.com>2019-02-20 02:53:08 +0530
committerSergei Golubchik <serg@mariadb.org>2019-02-22 00:35:40 +0100
commitd00f19e8325cd2f4beb10cc89f25ada8434099db (patch)
treed09ee2cc68ef9d7db9c9e7f6fdf175ef9597c647 /include/my_base.h
parent5b4d6595d26aaaf0bf8bb3c9171cf1da96306a7c (diff)
downloadmariadb-git-d00f19e8325cd2f4beb10cc89f25ada8434099db.tar.gz
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.
Diffstat (limited to 'include/my_base.h')
-rw-r--r--include/my_base.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/my_base.h b/include/my_base.h
index c36072c0bfa..8a8237ce8b2 100644
--- a/include/my_base.h
+++ b/include/my_base.h
@@ -99,7 +99,8 @@ enum ha_key_alg {
HA_KEY_ALG_BTREE= 1, /* B-tree, default one */
HA_KEY_ALG_RTREE= 2, /* R-tree, for spatial searches */
HA_KEY_ALG_HASH= 3, /* HASH keys (HEAP tables) */
- HA_KEY_ALG_FULLTEXT= 4 /* FULLTEXT (MyISAM tables) */
+ HA_KEY_ALG_FULLTEXT= 4, /* FULLTEXT (MyISAM tables) */
+ HA_KEY_ALG_LONG_HASH= 5 /* long BLOB keys */
};
/* Storage media types */