GBase 8a V95版本支持多列Hash的最大列数量

GBase 8a数据库集群,从V95版本开始,支持多列hash,用于改善数据倾斜问题。理论上其最大数量和列数量相同的2000个,但由于源数据表table_distribution里hash_column列最大长度是4096,实际列数会小于理论值。

测试2000个列的Hash分布列

直接报错 hash column string is too long for gbase system table。

gbase> source /home/gbase/t2000.sql
ERROR 1901 (HY000): hash column string is too long for gbase system table
gbase> use gbase;
Query OK, 0 rows affected (Elapsed: 00:00:00.00)

gbase> desc table_distribution;
+----------------------+---------------+------+-----+---------+-------+
| Field                | Type          | Null | Key | Default | Extra |
+----------------------+---------------+------+-----+---------+-------+
| index_name           | varchar(128)  | NO   | PRI | NULL    |       |
| dbName               | varchar(64)   | NO   |     | NULL    |       |
| tbName               | varchar(64)   | NO   |     | NULL    |       |
| isReplicate          | varchar(3)    | NO   |     | YES     |       |
| hash_column          | varchar(4096) | YES  |     | NULL    |       |
| lmt_storage_size     | bigint(20)    | YES  |     | NULL    |       |
| table_storage_size   | bigint(20)    | YES  |     | NULL    |       |
| is_nocopies          | varchar(3)    | NO   |     | YES     |       |
| data_distribution_id | bigint(8)     | NO   |     | NULL    |       |
| vc_id                | varchar(64)   | NO   | PRI | NULL    |       |
| mirror_vc_id         | varchar(64)   | YES  |     | NULL    |       |
+----------------------+---------------+------+-----+---------+-------+
11 rows in set (Elapsed: 00:00:00.00)

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