本文介绍了规则和拓扑类查询语句。
SHOW RULE [FROM tablename]
使用说明：
show rule：查看数据库下每一个逻辑表的拆分情况；show rule from tablename：查看数据库下指定逻辑表的拆分情况。
mysql> show rule;
+------+--------------+-----------+------------------+---------------------+--------------------+------------------+---------------------+--------------------+
| ID | TABLE_NAME | BROADCAST | DB_PARTITION_KEY | DB_PARTITION_POLICY | DB_PARTITION_COUNT | TB_PARTITION_KEY | TB_PARTITION_POLICY | TB_PARTITION_COUNT |
+------+--------------+-----------+------------------+---------------------+--------------------+------------------+---------------------+--------------------+
| 0 | dept_manager | 0 | | NULL | 1 | | NULL | 1 |
| 1 | emp | 0 | emp_no | hash | 8 | id | hash | 2 |
| 2 | example | 0 | shard_key | hash | 8 | | NULL | 1 |
+------+--------------+-----------+------------------+---------------------+--------------------+------------------+---------------------+--------------------+
3 rows in set (0.01 sec)
重要列详解：
- BROADCAST：是否为广播表（0：否，1：是）；
- DB_PARTITION_KEY：分库的拆分键，没有分库的话，值为空；
- DB_PARTITION_POLICY：分库的拆分策略，取值包括哈希或YYYYMM、YYYYDD、YYYYWEEK等日期策略；
- DB_PARTITION_COUNT：分库数；
- TB_PARTITION_KEY：分表的拆分键，没有分表的话，值为空；
- TB_PARTITION_POLICY：分表的拆分策略，取值包括哈希或MM、DD、MMDD、WEEK等日期策略；
- TB_PARTITION_COUNT：分表数。
SHOW FULL RULE [FROM tablename]
查看数据库下逻辑表的拆分规则，比SHOW RULE指令展示的信息更加详细。
mysql> show full rule;
+------+--------------+-----------+------------+-----------------------+----------------------------------------------------+-----------------------------------------------------+-----------------+------------------------------------+----------------+--------------------------------------------------+
| ID | TABLE_NAME | BROADCAST | JOIN_GROUP | ALLOW_FULL_TABLE_SCAN | DB_NAME_PATTERN | DB_RULES_STR | TB_NAME_PATTERN | TB_RULES_STR | PARTITION_KEYS | DEFAULT_DB_INDEX |
+------+--------------+-----------+------------+-----------------------+----------------------------------------------------+-----------------------------------------------------+-----------------+------------------------------------+----------------+--------------------------------------------------+
| 0 | dept_manager | 0 | NULL | 0 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS | NULL | dept_manager | NULL | NULL | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS |
| 1 | emp | 0 | NULL | 1 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_{0000}_RDS | ((#emp_no,1,8#).longValue().abs() % 8) | emp_{0} | ((#id,1,2#).longValue().abs() % 2) | emp_no id | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS |
| 2 | example | 0 | NULL | 1 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_{0000}_RDS | ((#shard_key,1,8#).longValue().abs() % 8).intdiv(1) | example | NULL | shard_key | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS |
+------+--------------+-----------+------------+-----------------------+----------------------------------------------------+-----------------------------------------------------+-----------------+------------------------------------+----------------+--------------------------------------------------+
3 rows in set (0.01 sec)
重要列详解：
- BROADCAST：是否为广播表（0：否，1：是）；
- JOIN_GROUP：保留字段，暂时无意义。
- ALLOW_FULL_TABLE_SCAN：分库分表在没有指定分表键值的情况下是否允许查询数据，如果配置为true，此时需要扫描每一个物理表来查找出符合条件的数据，简称为全表扫描；
- DB_NAME_PATTERN：DB_NAME_PATTERN中{}之间的0为占位符，执行SQL时会被DB_RULES_STR计算出的值替代，并保持位数。比如，DB_NAME_PATTERN的值为SEQ_{0000}_RDS，DB_RULES_STR的值为[1,2,3,4]，则会产生4个DB_NAME，分别为SEQ_0001_RDS、SEQ_0002_RDS、SEQ_0003_RDS、SEQ_0004_RDS；
- DB_RULES_STR：具体的分库规则；
- TB_NAME_PATTERN：TB_NAME_PATTERN中{}之间的0为占位符，执行SQL时会被TB_RULES_STR计算出的值替代，并保持位数。比如，TB_NAME_PATTERN的值为table_{00}，TB_RULES_STR的值为[1,2,3,4,5,6,7,8]，则会产生8张表，分别为table_01、table_02、table_03、table_04、table_05、table_06、table_07、table_08；
- TB_RULES_STR：分表规则；
- PARTITION_KEYS：分库和分表键集合，对于既分库又分表的情形，分库键在前，分表键在后；
- DEFAULT_DB_INDEX：单库单表存放的分库。
SHOW TOPOLOGY FROM tablename
查看指定逻辑表的拓扑分布，展示该逻辑表保存在哪些分库中，每个分库下包含哪些分表。
mysql> show topology from emp;
+------+--------------------------------------------------+------------+
| ID | GROUP_NAME | TABLE_NAME |
+------+--------------------------------------------------+------------+
| 0 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS | emp_0 |
| 1 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS | emp_1 |
| 2 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0001_RDS | emp_0 |
| 3 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0001_RDS | emp_1 |
| 4 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0002_RDS | emp_0 |
| 5 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0002_RDS | emp_1 |
| 6 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0003_RDS | emp_0 |
| 7 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0003_RDS | emp_1 |
| 8 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0004_RDS | emp_0 |
| 9 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0004_RDS | emp_1 |
| 10 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0005_RDS | emp_0 |
| 11 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0005_RDS | emp_1 |
| 12 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0006_RDS | emp_0 |
| 13 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0006_RDS | emp_1 |
| 14 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0007_RDS | emp_0 |
| 15 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0007_RDS | emp_1 |
+------+--------------------------------------------------+------------+
16 rows in set (0.01 sec)
SHOW PARTITIONS FROM tablename
查看分库分表键集合，分库键和分表键之间用逗号分割。如果最终结果有两个值，说明是既分库又分表的情形，第一个是分库键，第二个是分表键。如果结果只有一个值，说明是分库不分表的情形，该值是分库键。
mysql> show partitions from emp;
+-----------+
| KEYS |
+-----------+
| emp_no,id |
+-----------+
1 row in set (0.00 sec)
SHOW BROADCASTS
查看广播表列表。
mysql> show broadcasts;
+------+------------+
| ID | TABLE_NAME |
+------+------------+
| 0 | brd2 |
| 1 | brd_tbl |
+------+------------+
2 rows in set (0.01 sec)
SHOW DATASOURCES
查看底层存储信息，包含数据库名、数据库分组名、连接信息、用户名、底层存储类型、读写权重、连接池信息等。
mysql> show datasources;
+------+----------------------------+------------------------------------------------+--------------------------------------------------+----------------------------------------------------------------------------------+-----------+-------+------+------+------+--------------+----------+--------------+---------------+----------------------------------------------+-------------+--------------+
| ID | SCHEMA | NAME | GROUP | URL | USER | TYPE | INIT | MIN | MAX | IDLE_TIMEOUT | MAX_WAIT | ACTIVE_COUNT | POOLING_COUNT | ATOM | READ_WEIGHT | WRITE_WEIGHT |
+------+----------------------------+------------------------------------------------+--------------------------------------------------+----------------------------------------------------------------------------------+-----------+-------+------+------+------+--------------+----------+--------------+---------------+----------------------------------------------+-------------+--------------+
| 0 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0000_iiab_1 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0000 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0000_iiab | 10 | 10 |
| 1 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0001_iiab_2 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0001_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0001 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0001_iiab | 10 | 10 |
| 2 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0002_iiab_3 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0002_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0002 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0002_iiab | 10 | 10 |
| 3 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0003_iiab_4 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0003_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0003 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0003_iiab | 10 | 10 |
| 4 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0004_iiab_5 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0004_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0004 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0004_iiab | 10 | 10 |
| 5 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0005_iiab_6 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0005_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0005 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0005_iiab | 10 | 10 |
| 6 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0006_iiab_7 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0006_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0006 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0006_iiab | 10 | 10 |
| 7 | seq_test_1487767780814rgkk | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0007_iiab_8 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0007_RDS | jdbc:mysql://rds1ur80kcv8g3t6p3ol.mysql.rds.aliyuncs.com:3306/seq_test_wnjg_0007 | jnkinsea0 | mysql | 0 | 24 | 72 | 15 | 5000 | 0 | 1 | rds1ur80kcv8g3t6p3ol_seq_test_wnjg_0007_iiab | 10 | 10 |
+------+----------------------------+------------------------------------------------+--------------------------------------------------+----------------------------------------------------------------------------------+-----------+-------+------+------+------+--------------+----------+--------------+---------------+----------------------------------------------+-------------+--------------+
8 rows in set (0.01 sec)
重要列详解：
- SCHEMA：数据库名；
- GROUP：数据库分组名。分组的目标是管理多组数据完全相同的数据库，比如通过 RDS（MySQL）进行数据复制后的主备数据库。主要用来解决读写分离、主备切换的问题；
- URL：底层RDS（MySQL）的连接信息；
- TYPE：底层存储类型，目前只支持RDS（MySQL)；
- READ_WEIGHT：读权重。在主实例的读压力比较大的时候，可以通过读写分离功能将读流量进行分流，减轻RDS主实例的压力。PolarDB-X 1.0会自动识别读写流量，引导写流量进入RDS主实例，读流量则按配置的权重流向所有RDS实例；
- WRITE_WEIGHT：写权重。
SHOW NODE
查看物理库的读写次数（历史累计数据）、读写权重（历史累计数据）。
mysql> show node;
+------+--------------------------------------------------+-------------------+------------------+---------------------+--------------------+
| ID | NAME | MASTER_READ_COUNT | SLAVE_READ_COUNT | MASTER_READ_PERCENT | SLAVE_READ_PERCENT |
+------+--------------------------------------------------+-------------------+------------------+---------------------+--------------------+
| 0 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0000_RDS | 12 | 0 | 100% | 0% |
| 1 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0001_RDS | 0 | 0 | 0% | 0% |
| 2 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0002_RDS | 0 | 0 | 0% | 0% |
| 3 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0003_RDS | 0 | 0 | 0% | 0% |
| 4 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0004_RDS | 0 | 0 | 0% | 0% |
| 5 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0005_RDS | 0 | 0 | 0% | 0% |
| 6 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0006_RDS | 0 | 0 | 0% | 0% |
| 7 | SEQ_TEST_1487767780814RGKKSEQ_TEST_WNJG_0007_RDS | 0 | 0 | 0% | 0% |
+------+--------------------------------------------------+-------------------+------------------+---------------------+--------------------+
8 rows in set (0.01 sec)
重要列详解：
- MASTER_COUNT：RDS主实例处理的读写查询次数（历史累计数据）；
- SLAVE_COUNT：RDS备实例处理的只读查询次数（历史累计数据）；
- MASTER_PERCENT：RDS主实例处理的读写查询占比（注意该列显示的是累计的实际数据占比，并不是用户配置的百分比）；
- SLAVE_PERCENT：RDS备实例处理的读写查询占比（注意该列显示的是累计的实际数据占比，并不是用户配置的百分比）。
说明
- 事务中的只读查询会被发送到RDS主实例；
- 由于
MASTER_PERCENT，SLAVE_PERCENT这两列代表的是历史累计数据，更改读写权重的配比后，这几个数值并不能立即反应最新的读写权重配比，需累计一段比较长的时间才行。