# Index Full Scan（A）
```7
mysql> explain select count(*) from t1;
+------------------------------------+----------------+--------------+--------------------------------------+-------------------------------------------------+
| id                                          | estRows      | task          | access object                        | operator info                                      |
+-------------------------------------+----------------+--------------+-------------------------------------+-------------------------------------------------+
| StreamAgg_20                     | 1.00             | root          |                                              | funcs:count(Column#11)->Column#6 |
| └─IndexReader_21           | 1.00             | root          |                                              | index:StreamAgg_8                            |
|   └─StreamAgg_8              | 1.00             | cop[tikv]   |                                              | funcs:count(1)->Column#11               |
|     └─IndexFullScan_19     | 2560000.00 | cop[tikv]   | table:t1, index:t1_ind_id(id)  | keep order:false                                 |
+-------------------------------------+-----------------+-------------+--------------------------------------+-------------------------------------------------+
4 rows in set (0.01 sec)
```
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Index Full Scan