> ## Documentation Index
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> System table listing hypothetical (what-if) indexes defined in the current session

# system.hypothetical_indexes

Lists every hypothetical (what-if) skip index defined in the current session. See [`CREATE HYPOTHETICAL INDEX`](/reference/statements/hypothetical-index#create-hypothetical-index) and [`EXPLAIN WHATIF`](/reference/statements/explain#explain-whatif).

The contents are session-scoped: each connection sees only its own hypothetical indexes, and the table is empty when no indexes have been created in the current session.

The current `(database, table)` are resolved by UUID at query time, so they reflect `RENAME TABLE` and entries for dropped tables are hidden automatically.

<h2 id="columns">
  Columns
</h2>

| Column        | Type     | Description                                                           |
| ------------- | -------- | --------------------------------------------------------------------- |
| `database`    | `String` | Target database.                                                      |
| `table`       | `String` | Target table.                                                         |
| `name`        | `String` | Index name.                                                           |
| `type`        | `String` | Index type (`minmax`, `set`, `bloom_filter`, etc.).                   |
| `type_full`   | `String` | Index type expression including arguments, e.g. `bloom_filter(0.01)`. |
| `expression`  | `String` | Index expression as written in `CREATE HYPOTHETICAL INDEX`.           |
| `granularity` | `UInt64` | Number of data granules per index granule.                            |

<h2 id="example">
  Example
</h2>

```sql theme={null}
CREATE HYPOTHETICAL INDEX i1 ON t (b) TYPE bloom_filter(0.01)  GRANULARITY 1;
CREATE HYPOTHETICAL INDEX i2 ON t (b) TYPE bloom_filter(0.001) GRANULARITY 1;

SELECT database, table, name, type, type_full, expression, granularity
FROM system.hypothetical_indexes;
```

```text theme={null}
┌─database─┬─table─┬─name─┬─type─────────┬─type_full───────────┬─expression─┬─granularity─┐
│ default  │ t     │ i1   │ bloom_filter │ bloom_filter(0.01)  │ b          │           1 │
│ default  │ t     │ i2   │ bloom_filter │ bloom_filter(0.001) │ b          │           1 │
└──────────┴───────┴──────┴──────────────┴─────────────────────┴────────────┴─────────────┘
```

`type` is the base type name and `type_full` includes the arguments, so users can distinguish between parametrized variants like `bloom_filter(0.01)` and `bloom_filter(0.001)`.

<h2 id="see-also">
  See also
</h2>

* [`CREATE HYPOTHETICAL INDEX`](/reference/statements/hypothetical-index#create-hypothetical-index)
* [`EXPLAIN WHATIF`](/reference/statements/explain#explain-whatif)