PolarDB:Instructions

Automatic request distribution among row store and IMCI nodes

PolarDB automatically routes each read request to either a read-only IMCI node or a read-only row store node based on the estimated execution cost (number of rows scanned). Use this mode when a single application sends both OLAP and OLTP requests.

On the cluster details page, go to the Database Connections section. For the Cluster Endpoint, set Transactional/Analytical Processing Splitting to On.

Manual request distribution among row store and IMCI nodes

If different applications handle OLAP and OLTP requests separately, create a custom endpoint that includes only Read-only IMCI Nodes as service nodes. Point your OLAP application to this endpoint.

On the cluster details page, go to the Database Connections section and create a custom endpoint. Set the service nodes to Read-only IMCI Nodes only.

Manually add IMCIs

IMCI supports the following DDL statements to add or remove column indexes on your tables:

To preserve existing table comments, append COLUMNAR=1 before them: ALTER TABLE <table_name> COMMENT 'COLUMNAR=1 <original comment>';

When adding IMCIs in batches at the database or table level, the table comment is automatically updated to 'COLUMNAR=1 <original comment>'.

Automatically add IMCIs

The AutoIndex feature monitors slow queries and automatically creates IMCIs to accelerate them. As workloads change, AutoIndex continuously adjusts the IMCI strategy to maintain optimal performance — without requiring manual query analysis.

On the cluster details page, enable the AutoIndex feature:

IMCI execution plan (horizontal tree format)

If the query uses IMCI, the output shows a horizontal tree structure:

+----+----------------------------+----------+--------+--------+-----------------------------------------------------------------------------+
| ID | Operator                   | Name     | E-Rows | E-Cost | Extra Info                                                                  |
+----+----------------------------+----------+--------+--------+-----------------------------------------------------------------------------+
|  1 | Select Statement           |          |        |        | IMCI Execution Plan (max_dop = 4, max_query_mem = 858993459)                |
|  2 | └─Sort                     |          |        |        | Sort Key: revenue DESC,o_orderdate ASC                                      |
|  3 |   └─Hash Groupby           |          |        |        | Group Key: (lineitem.L_ORDERKEY, orders.O_ORDERDATE, orders.O_SHIPPRIORITY) |
|  4 |     └─Hash Join            |          |        |        | Join Cond: orders.O_ORDERKEY = lineitem.L_ORDERKEY                          |
|  5 |       ├─Hash Join          |          |        |        | Join Cond: customer.C_CUSTKEY = orders.O_CUSTKEY                            |
|  6 |       │ ├─Table Scan       | customer |        |        | Cond: (C_MKTSEGMENT = "BUILDING")                                           |
|  7 |       │ └─Table Scan       | orders   |        |        | Cond: (O_ORDERDATE < 03/24/1995)                                            |
|  8 |       └─Table Scan         | lineitem |        |        | Cond: (L_SHIPDATE > 03/24/1995)                                             |
+----+----------------------------+----------+--------+--------+-----------------------------------------------------------------------------+
8 rows in set (0.01 sec)

The key signal is the Extra Info field on row 1: IMCI Execution Plan. This confirms the query is running on IMCI.

Row store execution plan

If the query uses the row store instead, the output follows the standard MySQL tabular format without the IMCI Execution Plan header:

+----+-------------+----------+------------+------+--------------------+------------+---------+-----------------------------+--------+----------+----------------------------------------------+
| id | select_type | table    | partitions | type | possible_keys      | key        | key_len | ref                         | rows   | filtered | Extra                                        |
+----+-------------+----------+------------+------+--------------------+------------+---------+-----------------------------+--------+----------+----------------------------------------------+
|  1 | SIMPLE      | customer | NULL       | ALL  | PRIMARY            | NULL       | NULL    | NULL                        | 147630 |    10.00 | Using where; Using temporary; Using filesort |
|  1 | SIMPLE      | orders   | NULL       | ref  | PRIMARY,ORDERS_FK1 | ORDERS_FK1 | 4       | tpch100g.customer.C_CUSTKEY |     14 |    33.33 | Using where                                  |
|  1 | SIMPLE      | lineitem | NULL       | ref  | PRIMARY            | PRIMARY    | 4       | tpch100g.orders.O_ORDERKEY  |      4 |    33.33 | Using where                                  |
+----+-------------+----------+------------+------+--------------------+------------+---------+-----------------------------+--------+----------+----------------------------------------------+
3 rows in set, 1 warning (0.00 sec)

For more information, see Check whether a query can use IMCIs.