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# CLI Specific Functions
`datafusion-cli` comes with build-in functions that are not included in the
DataFusion SQL engine by default. These functions are:
## `parquet_metadata`
The `parquet_metadata` table function can be used to inspect detailed metadata
about a parquet file such as statistics, sizes, and other information. This can
be helpful to understand how parquet files are structured.
For example, to see information about the `"WatchID"` column in the
`hits.parquet` file, you can use:
```sql
SELECT path_in_schema, row_group_id, row_group_num_rows, stats_min, stats_max, total_compressed_size
FROM parquet_metadata('hits.parquet')
WHERE path_in_schema = '"WatchID"'
LIMIT 3;
+----------------+--------------+--------------------+---------------------+---------------------+-----------------------+
| path_in_schema | row_group_id | row_group_num_rows | stats_min | stats_max | total_compressed_size |
+----------------+--------------+--------------------+---------------------+---------------------+-----------------------+
| "WatchID" | 0 | 450560 | 4611687214012840539 | 9223369186199968220 | 3883759 |
| "WatchID" | 1 | 612174 | 4611689135232456464 | 9223371478009085789 | 5176803 |
| "WatchID" | 2 | 344064 | 4611692774829951781 | 9223363791697310021 | 3031680 |
+----------------+--------------+--------------------+---------------------+---------------------+-----------------------+
3 rows in set. Query took 0.053 seconds.
```
The returned table has the following columns for each row for each column chunk
in the file. Please refer to the [Parquet Documentation] for more information in
the meaning of these fields.
[parquet documentation]: https://parquet.apache.org/
| column_name | data_type | Description |
| ----------------------- | --------- | --------------------------------------------------------------------------------------------------- |
| filename | Utf8 | Name of the file |
| row_group_id | Int64 | Row group index the column chunk belongs to |
| row_group_num_rows | Int64 | Count of rows stored in the row group |
| row_group_num_columns | Int64 | Total number of columns in the row group (same for all row groups) |
| row_group_bytes | Int64 | Number of bytes used to store the row group (not including metadata) |
| column_id | Int64 | ID of the column |
| file_offset | Int64 | Offset within the file that this column chunk's data begins |
| num_values | Int64 | Total number of values in this column chunk |
| path_in_schema | Utf8 | "Path" (column name) of the column chunk in the schema |
| type | Utf8 | Parquet data type of the column chunk |
| stats_min | Utf8 | The minimum value for this column chunk, if stored in the statistics, cast to a string |
| stats_max | Utf8 | The maximum value for this column chunk, if stored in the statistics, cast to a string |
| stats_null_count | Int64 | Number of null values in this column chunk, if stored in the statistics |
| stats_distinct_count | Int64 | Number of distinct values in this column chunk, if stored in the statistics |
| stats_min_value | Utf8 | Same as `stats_min` |
| stats_max_value | Utf8 | Same as `stats_max` |
| compression | Utf8 | Block level compression (e.g. `SNAPPY`) used for this column chunk |
| encodings | Utf8 | All block level encodings (e.g. `[PLAIN_DICTIONARY, PLAIN, RLE]`) used for this column chunk |
| index_page_offset | Int64 | Offset in the file of the [`page index`], if any |
| dictionary_page_offset | Int64 | Offset in the file of the dictionary page, if any |
| data_page_offset | Int64 | Offset in the file of the first data page, if any |
| total_compressed_size | Int64 | Number of bytes the column chunk's data after encoding and compression (what is stored in the file) |
| total_uncompressed_size | Int64 | Number of bytes the column chunk's data after encoding |
[`page index`]: https://github.com/apache/parquet-format/blob/master/PageIndex.md
## `metadata_cache`
The `metadata_cache` function shows information about the default File Metadata Cache that is used by the
[`ListingTable`] implementation in DataFusion. This cache is used to speed up
reading metadata from files when scanning directories with many files.
For example, after creating a table with the [CREATE EXTERNAL TABLE](../sql/ddl.md#create-external-table)
command:
```sql
> create external table hits
stored as parquet
location 's3://clickhouse-public-datasets/hits_compatible/athena_partitioned/';
```
You can inspect the metadata cache by querying the `metadata_cache` function:
```sql
> select * from metadata_cache();
+----------------------------------------------------+---------------------+-----------------+---------------------------------------+---------+---------------------+------+------------------+
| path | file_modified | file_size_bytes | e_tag | version | metadata_size_bytes | hits | extra |
+----------------------------------------------------+---------------------+-----------------+---------------------------------------+---------+---------------------+------+------------------+
| hits_compatible/athena_partitioned/hits_61.parquet | 2022-07-03T15:40:34 | 117270944 | "5db11cad1ca0d80d748fc92c914b010a-6" | NULL | 212949 | 0 | page_index=false |
| hits_compatible/athena_partitioned/hits_32.parquet | 2022-07-03T15:37:17 | 94506004 | "2f7db49a9fe242179590b615b94a39d2-5" | NULL | 278157 | 0 | page_index=false |
| hits_compatible/athena_partitioned/hits_40.parquet | 2022-07-03T15:38:07 | 142508647 | "9e5852b45a469d5a05bf270a286eab8a-8" | NULL | 212917 | 0 | page_index=false |
| hits_compatible/athena_partitioned/hits_93.parquet | 2022-07-03T15:44:07 | 127987774 | "751100bf0dac7d489b9836abf3108b99-7" | NULL | 278318 | 0 | page_index=false |
| . |
+----------------------------------------------------+---------------------+-----------------+---------------------------------------+---------+---------------------+------+------------------+
```
Since `metadata_cache` is a normal table function, you can use it in most places you can use
a table reference.
For example, to get the total size consumed by the cached entries:
```sql
> select sum(metadata_size_bytes) from metadata_cache();
+-------------------------------------------+
| sum(metadata_cache().metadata_size_bytes) |
+-------------------------------------------+
| 22972345 |
+-------------------------------------------+
```
The columns of the returned table are:
| column_name | data_type | Description |
| ------------------- | --------- | ----------------------------------------------------------------------------------------- |
| path | Utf8 | File path relative to the object store / filesystem root |
| file_modified | Timestamp | Last modified time of the file |
| file_size_bytes | UInt64 | Size of the file in bytes |
| e_tag | Utf8 | [Entity Tag] (ETag) of the file if available |
| version | Utf8 | Version of the file if available (for object stores that support versioning) |
| metadata_size_bytes | UInt64 | Size of the cached metadata in memory (not its thrift encoded form) |
| hits | UInt64 | Number of times the cached metadata has been accessed |
| extra | Utf8 | Extra information about the cached metadata (e.g., if page index information is included) |
## `statistics_cache`
Similarly to the `metadata_cache`, the `statistics_cache` function can be used to show information
about the File Statistics Cache that is used by the [`ListingTable`] implementation in DataFusion.
For the statistics to be collected, the config `datafusion.execution.collect_statistics` must be
enabled.
You can inspect the statistics cache by querying the `statistics_cache` function. For example:
```sql
> select * from statistics_cache();
+------------------+---------------------+-----------------+------------------------+---------+-----------------+-------------+--------------------+-----------------------+
| path | file_modified | file_size_bytes | e_tag | version | num_rows | num_columns | table_size_bytes | statistics_size_bytes |
+------------------+---------------------+-----------------+------------------------+---------+-----------------+-------------+--------------------+-----------------------+
| .../hits.parquet | 2022-06-25T22:22:22 | 14779976446 | 0-5e24d1ee16380-370f48 | NULL | Exact(99997497) | 105 | Exact(36445943240) | 0 |
+------------------+---------------------+-----------------+------------------------+---------+-----------------+-------------+--------------------+-----------------------+
```
The columns of the returned table are:
| column_name | data_type | Description |
| --------------------- | --------- | ---------------------------------------------------------------------------- |
| path | Utf8 | File path relative to the object store / filesystem root |
| file_modified | Timestamp | Last modified time of the file |
| file_size_bytes | UInt64 | Size of the file in bytes |
| e_tag | Utf8 | [Entity Tag] (ETag) of the file if available |
| version | Utf8 | Version of the file if available (for object stores that support versioning) |
| num_rows | Utf8 | Number of rows in the table |
| num_columns | UInt64 | Number of columns in the table |
| table_size_bytes | Utf8 | Size of the table, in bytes |
| statistics_size_bytes | UInt64 | Size of the cached statistics in memory |
## `list_files_cache`
The `list_files_cache` function shows information about the `ListFilesCache` that is used by the [`ListingTable`] implementation in DataFusion. When creating a [`ListingTable`], DataFusion lists the files in the table's location and caches results in the `ListFilesCache`. Subsequent queries against the same table can reuse this cached information instead of re-listing the files. Cache entries are scoped to tables.
You can inspect the cache by querying the `list_files_cache` function. For example,
```sql
> set datafusion.runtime.list_files_cache_ttl = "30s";
> create external table overturemaps
stored as parquet
location 's3://overturemaps-us-west-2/release/2025-12-17.0/theme=base/type=infrastructure';
0 row(s) fetched.
> select table, path, metadata_size_bytes, expires_in, unnest(metadata_list)['file_size_bytes'] as file_size_bytes, unnest(metadata_list)['e_tag'] as e_tag from list_files_cache() limit 10;
+--------------+-----------------------------------------------------+---------------------+-----------------------------------+-----------------+---------------------------------------+
| table | path | metadata_size_bytes | expires_in | file_size_bytes | e_tag |
+--------------+-----------------------------------------------------+---------------------+-----------------------------------+-----------------+---------------------------------------+
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 999055952 | "35fc8fbe8400960b54c66fbb408c48e8-60" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 975592768 | "8a16e10b722681cdc00242564b502965-59" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 1082925747 | "24cd13ddb5e0e438952d2499f5dabe06-65" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 1008425557 | "37663e31c7c64d4ef355882bcd47e361-61" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 1065561905 | "4e7c50d2d1b3c5ed7b82b4898f5ac332-64" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 1045655427 | "8fff7e6a72d375eba668727c55d4f103-63" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 1086822683 | "b67167d8022d778936c330a52a5f1922-65" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 1016732378 | "6d70857a0473ed9ed3fc6e149814168b-61" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 991363784 | "c9cafb42fcbb413f851691c895dd7c2b-60" |
| overturemaps | release/2025-12-17.0/theme=base/type=infrastructure | 2750 | 0 days 0 hours 0 mins 25.264 secs | 1032469715 | "7540252d0d67158297a67038a3365e0f-62" |
+--------------+-----------------------------------------------------+---------------------+-----------------------------------+-----------------+---------------------------------------+
```
The columns of the returned table are:
| column_name | data_type | Description |
| ------------------- | ------------ | ----------------------------------------------------------------------------------------- |
| table | Utf8 | Name of the table |
| path | Utf8 | File path relative to the object store / filesystem root |
| metadata_size_bytes | UInt64 | Size of the cached metadata in memory (not its thrift encoded form) |
| expires_in | Duration(ms) | Last modified time of the file |
| metadata_list | List(Struct) | List of metadatas, one for each file under the path. |
A metadata struct in the metadata_list contains the following fields:
```text
{
"file_path": "release/2025-12-17.0/theme=base/type=infrastructure/part-00000-d556e455-e0c5-4940-b367-daff3287a952-c000.zstd.parquet",
"file_modified": "2025-12-17T22:20:29",
"file_size_bytes": 999055952,
"e_tag": "35fc8fbe8400960b54c66fbb408c48e8-60",
"version": null
}
```
[`listingtable`]: https://docs.rs/datafusion/latest/datafusion/datasource/listing/struct.ListingTable.html
[entity tag]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag