网站空间不够用怎么办,网络体系结构,网站后台登陆破解,嘉兴网站模板建站在大数据系统中#xff0c;如无特别需要#xff0c;建议 collation 指定为 utf8mb4_bin。 utf8mb4_bin是一种二进制的排序规则#xff0c;比较字符串时直接比较字符串的二进制值#xff0c;不需要进行复杂的字符比较和排序运算#xff0c;这样可以有效减少CPU的使用…在大数据系统中如无特别需要建议 collation 指定为 utf8mb4_bin。 utf8mb4_bin是一种二进制的排序规则比较字符串时直接比较字符串的二进制值不需要进行复杂的字符比较和排序运算这样可以有效减少CPU的使用提高查询效率特别是在涉及到大量数据操作时性能优势更为明显。 在 AP 场景使用 OceanBase 时你可以在租户级别设置这两个值作为默认配置以获得最佳的默认性能 set global collation_connection utf8mb4_bin; set global collation_server utf8mb4_bin;utf8mb4 是编码格式设置 collation 为 bin 不会影响内存的存储格式不会造成字符集不兼容等问题它仅仅影响排序过程中的排序规则。 使用 bin 排序和不使用 bin 排序的详细对比如下 OceanBase(admintest)show variables like collation_server; -------------------------------------- | Variable_name | Value | -------------------------------------- | collation_server | utf8mb4_general_ci | -------------------------------------- 1 row in set (0.007 sec)OceanBase(admintest)create table t1 (c1 bigint primary key, c2 varchar(10)); Query OK, 0 rows affected (0.102 sec)OceanBase(admintest)create table t2 (c1 bigint primary key, c2 varchar(10)) charsetutf8mb4 collateutf8mb4_bin; Query OK, 0 rows affected (0.089 sec)OceanBase(admintest)show create table t1\G *************************** 1. row ***************************Table: t1 Create Table: CREATE TABLE t1 (c1 bigint(20) NOT NULL,c2 varchar(10) DEFAULT NULL,PRIMARY KEY (c1) ) DEFAULT CHARSET utf8mb4 ROW_FORMAT DYNAMIC COMPRESSION zstd_1.3.8 REPLICA_NUM 2 BLOCK_SIZE 16384 USE_BLOOM_FILTER FALSE TABLET_SIZE 134217728 PCTFREE 0 1 row in set (0.011 sec)OceanBase(admintest)show create table t2\G *************************** 1. row ***************************Table: t2 Create Table: CREATE TABLE t2 (c1 bigint(20) NOT NULL,c2 varchar(10) COLLATE utf8mb4_bin DEFAULT NULL,PRIMARY KEY (c1) ) DEFAULT CHARSET utf8mb4 COLLATE utf8mb4_bin ROW_FORMAT DYNAMIC COMPRESSION zstd_1.3.8 REPLICA_NUM 2 BLOCK_SIZE 16384 USE_BLOOM_FILTER FALSE TABLET_SIZE 134217728 PCTFREE 0 1 row in set (0.011 sec)OceanBase(admintest)insert /* append enable_parallel_dml parallel(4) */ into t1 select random(), randstr(1, 6) from table(generator(1000000)); Query OK, 1000000 rows affected (8.629 sec) Records: 1000000 Duplicates: 0 Warnings: 0OceanBase(admintest)insert /* append enable_parallel_dml parallel(4) */ into t2 select * from t1; Query OK, 1000000 rows affected (7.115 sec) Records: 1000000 Duplicates: 0 Warnings: 0OceanBase(admintest)select * from t1 order by c2 limit 999998, 1; ---------------------------- | c1 | c2 | ---------------------------- | -8614823888367694260 | 5 | ---------------------------- 1 row in set (1.050 sec)OceanBase(admintest)select * from t2 order by c2 limit 999998, 1; ---------------------------- | c1 | c2 | ---------------------------- | -8614823888367694260 | 5 | ---------------------------- 1 row in set (0.876 sec)OceanBase(admintest)select * from t1 order by c2 limit 999998, 1; ---------------------------- | c1 | c2 | ---------------------------- | -8614823888367694260 | 5 | ---------------------------- 1 row in set (1.053 sec)OceanBase(admintest)select * from t2 order by c2 limit 999998, 1; ---------------------------- | c1 | c2 | ---------------------------- | -8614823888367694260 | 5 | ---------------------------- 1 row in set (0.844 sec)