Support `select .. from 'data.parquet'` files in SQL from any `SessionContext` (optionally)

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do. Similarly to https://github.com/apache/arrow-datafusion/issues/4580, I think systems built with datafusion would like to allow their users to quickly explore a parquet file with minimal typing

Today have to type a verbose CREATE EXTERNAL TABLE... command

It is critical that this feature can be enabled/disabled so that DataFusion can provide read only access (rather than access to the file system as that would be a security hole)

I am marking this as a good first issue because I think all the code needed exists and there is a solution sketch below -- it should be a matter of coding that doesn't require huge existing knowledge of the datafusion codebase and would be a good exercise in getting familiar

❯ CREATE EXTERNAL TABLE all_types_tiny_pages STORED AS PARQUET LOCATION './parquet-testing/data/alltypes_tiny_pages.parquet';

❯ select * from all_types_tiny_pages limit 10;
+-----+----------+-------------+--------------+---------+------------+-----------+--------------------+-----------------+------------+-------------------------+------+-------+
| id  | bool_col | tinyint_col | smallint_col | int_col | bigint_col | float_col | double_col         | date_string_col | string_col | timestamp_col           | year | month |
+-----+----------+-------------+--------------+---------+------------+-----------+--------------------+-----------------+------------+-------------------------+------+-------+
| 122 | true     | 2           | 2            | 2       | 20         | 2.2       | 20.2               | 01/13/09        | 2          | 2009-01-13T01:02:05.410 | 2009 | 1     |
| 123 | false    | 3           | 3            | 3       | 30         | 3.3       | 30.299999999999997 | 01/13/09        | 3          | 2009-01-13T01:03:05.430 | 2009 | 1     |
| 124 | true     | 4           | 4            | 4       | 40         | 4.4       | 40.4               | 01/13/09        | 4          | 2009-01-13T01:04:05.460 | 2009 | 1     |
| 125 | false    | 5           | 5            | 5       | 50         | 5.5       | 50.5               | 01/13/09        | 5          | 2009-01-13T01:05:05.500 | 2009 | 1     |
| 126 | true     | 6           | 6            | 6       | 60         | 6.6       | 60.599999999999994 | 01/13/09        | 6          | 2009-01-13T01:06:05.550 | 2009 | 1     |
| 127 | false    | 7           | 7            | 7       | 70         | 7.7       | 70.7               | 01/13/09        | 7          | 2009-01-13T01:07:05.610 | 2009 | 1     |
| 128 | true     | 8           | 8            | 8       | 80         | 8.8       | 80.8               | 01/13/09        | 8          | 2009-01-13T01:08:05.680 | 2009 | 1     |
| 129 | false    | 9           | 9            | 9       | 90         | 9.9       | 90.89999999999999  | 01/13/09        | 9          | 2009-01-13T01:09:05.760 | 2009 | 1     |
| 130 | true     | 0           | 0            | 0       | 0          | 0         | 0                  | 01/14/09        | 0          | 2009-01-14T01:10:05.850 | 2009 | 1     |
| 131 | false    | 1           | 1            | 1       | 10         | 1.1       | 10.1               | 01/14/09        | 1          | 2009-01-14T01:11:05.850 | 2009 | 1     |
+-----+----------+-------------+--------------+---------+------------+-----------+--------------------+-----------------+------------+-------------------------+------+-------+
10 rows in set. Query took 0.039 seconds.

@unconsolable added this ability into datafusion-cli as part of https://github.com/apache/arrow-datafusion/pull/4838 (❤️ )

❯ select * from '/Users/alamb/.influxdb_iox//1/8/1/6/e24b6549-f76c-4fc0-a4f4-152ed60eb4e3.parquet';
+---------+---------------------+------+---------+----------+---------+---------------------+-------+---------+---------+
| blocked | host                | idle | running | sleeping | stopped | time                | total | unknown | zombies |
+---------+---------------------+------+---------+----------+---------+---------------------+-------+---------+---------+
| 0       | MacBook-Pro-8.local | 0    | 2       | 697      | 0       | 2022-07-18T21:05:10 | 700   | 0       | 1       |
| 0       | MacBook-Pro-8.local | 0    | 2       | 696      | 0       | 2022-07-18T21:05:20 | 699   | 0       | 1       |
+---------+---------------------+------+---------+----------+---------+---------------------+-------+---------+---------+
2 rows in set. Query took 0.079 seconds.

Describe the solution you'd like

I would like to be able to select directly from files (parquet, or other) from any datafusion session context, controlled by a setting. For example

❯ select * from 'foo.parquet';
Plan("table 'foo.parquet' not found")
❯ -- turn on the setting
❯ set datafusion.catalog.files_as_tables = true;
0 rows in set. Query took 0.000 seconds.
❯ select * from 'foo.parquet';
+---------+---------------------+------+---------+----------+---------+---------------------+-------+---------+---------+
| blocked | host                | idle | running | sleeping | stopped | time                | total | unknown | zombies |
+---------+---------------------+------+---------+----------+---------+---------------------+-------+---------+---------+
| 0       | MacBook-Pro-8.local | 0    | 2       | 697      | 0       | 2022-07-18T21:05:10 | 700   | 0       | 1       |
| 0       | MacBook-Pro-8.local | 0    | 2       | 696      | 0       | 2022-07-18T21:05:20 | 699   | 0       | 1       |
+---------+---------------------+------+---------+----------+---------+---------------------+-------+---------+---------+
2 rows in set. Query took 0.079 seconds.

Suggested Solution Sketch

1. Add a new config setting files_as_tables similar to information_schema: https://github.com/apache/arrow-datafusion/blob/f9b72f4230687b884a92f79d21762578d3d56281/datafusion/common/src/config.rs#L167-L169

2. Add code to make a ListingTable in resolve_table_ref: https://github.com/apache/arrow-datafusion/blob/f9b72f4230687b884a92f79d21762578d3d56281/datafusion/core/src/execution/context.rs#L1551-L1560 (follow the model in https://github.com/apache/arrow-datafusion/pull/4838/files#diff-6353c2268d4d11abf8c1b8804a263db74a3b765a7302fc61caea3924256b52c7R142-R155)

3. Move implementation from datafusion-cli; remove provider added in https://github.com/apache/arrow-datafusion/pull/4838 and use new setting instead https://github.com/apache/arrow-datafusion/blob/f9b72f4230687b884a92f79d21762578d3d56281/datafusion-cli/src/main.rs#L100 Add slt tests, similar to existing ones (should be able to refer to existing .parquet / .csv files in testing directories): https://github.com/apache/arrow-datafusion/blob/f9b72f4230687b884a92f79d21762578d3d56281/datafusion/core/tests/sqllogictests/test_files/information_schema.slt#L46

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context

Here is how information schema works, for reference.

❯ set datafusion.catalog.information_schema = false;
0 rows in set. Query took 0.002 seconds.
❯ show tables;
Plan("SHOW TABLES is not supported unless information_schema is enabled")
❯ set datafusion.catalog.information_schema = true;
0 rows in set. Query took 0.000 seconds.
❯ show tables;
+---------------+--------------------+-------------+------------+
| table_catalog | table_schema       | table_name  | table_type |
+---------------+--------------------+-------------+------------+
| datafusion    | information_schema | tables      | VIEW       |
| datafusion    | information_schema | views       | VIEW       |
| datafusion    | information_schema | columns     | VIEW       |
| datafusion    | information_schema | df_settings | VIEW       |
+---------------+--------------------+-------------+------------+
4 rows in set. Query took 0.005 seconds.
❯ 

[matthewwillian]

I'm happy to take on this issue if no one else is already working on it!

[timvw]

Enhancement: Instead of only relying on file extension name (as per the current implementation) we could use some inspiration from duckdb for loading/importing data such that the user can indicate the format to use (https://duckdb.org/docs/data/csv)

Eg: "select ... from read_csv('filename', options)" instead of plain "select .. from 'filename'"..

This would be helpful in cases where files are named "hitdata.tsv" (https://experienceleague.adobe.com/docs/analytics/export/analytics-data-feed/data-feed-overview.html?lang=en)

[alamb]

I would love to see a function like read_csv or maybe read_file('filename') 👍

[unconsolable]

IMHO, these are table functions. I wonder does datafusion support table function now? ref. https://github.com/apache/arrow-datafusion/issues/3773

[alamb]

I agree with @unconsolable

[holicc]

I would love to see a function like read_csv or maybe read_file('filename') 👍

@alamb Are there any processes here? I'd like to try this.

[alamb]

@alamb Are there any processes here? I'd like to try this.

Hi @holicc -- no there is no progress on this issue that I know of.

Given the conversation above, it seems like there are two options:

1. Implement table functions (like read_file(...))
2. Implement some automatic catalog (the way that datafusion-cli does)

Have you given any thought to the approach to take?

[holicc]

@alamb Maybe both options are good. Like DuckDB (see documentation: http://duckdb.org/docs/archive/0.8.1/data/csv/overview):

1. When using read_file, you might need to specify file parse options, e.g. read_csv('simple.csv', delim='|', header=True).
2. The way that datafusion-cli does it also makes it convenient for us.

[alamb]

Having both makes sense to me.

I would say making a table function is likely a large piece of design work as there is no pre-existing model to follow for table functions (we probably need some sort of registry and pass that expands them out to some sort of TableProvider

[holicc]

I found out that we are using the sqlparser crate to parse SQL. Therefore, we can modify the parsed statements with the visitorMut trait, collect all tables, and replace them with a new table name. Finally, we can use the register_csv API to register those tables. This way may be a little tricky.

[alamb]

I found out that we are using the sqlparser crate to parse SQL. Therefore, we can modify the parsed statements with the visitorMut trait, collect all tables, and replace them with a new table name. Finally, we can use the register_csv API to register those tables. This way may be a little tricky.

yes, we could

I would recommend thinking a little more holistically about table functions

Specifically adding them to the registry: https://docs.rs/datafusion/latest/datafusion/execution/registry/trait.FunctionRegistry.html

And then teaching our SQL planner how to look up those functions

[holicc]

IMHO, TableFunction is essentially a TableProvider. Therefore, we can make a new trait that returns a TableProvider and execute the table function in create_relation and using TableScan to build a LogicPlan

Add a new trait:

#[async_trait]
pub trait TableFunction: Sync + Send {
    async fn execute(
        &self,
        table: impl Into<OwnedTableReference>,
        state: &SessionState,
    ) -> Result<Arc<dyn TableProvider>>;
}

add new method to FunctionRegistry

pub trait FunctionRegistry {
    ...
    /// Returns a reference to the table function named `name`.
    fn table_function(&self, name: &str) -> Result<Arc<dyn TableFunction>>;
}

[alamb]

Therefore, we can make a new trait that returns a TableProvider and execute the table function in create_relation and using TableScan to build a LogicPlan

I think one big difference is that a table function can take some number of parameters

SELECT * FROM read_parquet('test.parquet');

The table function is read_parquet(..) which gets arguments of a string test.parquet.

The SQL parser will give the argument as an Expr. https://docs.rs/sqlparser/latest/sqlparser/ast/enum.TableFactor.html#variant.TableFunction

So perhaps we could make the TableFuncton trait like:

#[async_trait]
pub trait TableFunction: Sync + Send {
    async fn execute(
        &self,
        arg: Expr,
        state: &SessionState,
    ) -> Result<Arc<dyn TableProvider>>;
}

To take that arbitrary argument in

[timvw]

And what about multiple arguments? Eg: read_csv('blah.csv', delimiter = ';', ... )

[alamb]

And what about multiple arguments? Eg: read_csv('blah.csv', delimiter = ';', ... )

Good point @timvw -- we would probably want to allow that in the API. I tried it out and it does appear that the sql parser supports that kind of syntax 👍

❯ select foo from read_parquet('foo.parquet', 'bar');
Error during planning: table 'datafusion.public.read_parquet' not found

[holicc]

@alamb I'm having trouble inferring the schema because I can't get a SessionState from the ContextProvider. Can you help me?

let listing_options = CsvReadOptions::default().to_listing_options(&self.config);
let url = ListingTableUrl::parse(file_path)?;
let cfg = ListingTableConfig::new(url)
            .with_listing_options(listing_options)
            .with_schema(Arc::new(arrow_schema::Schema::empty()));

// FIXME How to get a SessionState?
cfg.infer_schema(state);

let table = ListingTable::try_new(cfg)?;
let source = Arc::new(DefaultTableSource::new(Arc::new(table)));

[alamb]

Hi @holicc -- I don't think it is possible to do this in the SQL parser level (as the the datafusion crate depends on the datafusion-sql crate, not the reverse.

Thus I think the resolution from a table name to a ListingTable may have to happen later in the process. In the Suggested Solution Sketch above I tried to suggest taking inspiration from the dynamic lookup works today in datafusion-cli. Perhaps we can follow the same model here

[alamb]

cc @goldmedal here is an issue that describes supporting reading style urls as tables

select * from 's3://foo/bar.parquet'

Probably a good first step would be to move the DynamicFileCatalogProvider https://github.com/apache/datafusion/blob/088ad010a6ceaa6a2e810d418a2370e45acf3d54/datafusion-cli/src/catalog.rs#L79 into the core somewhere (but not registering it with SessionContext)

Then a second step would be to add an option (like the information_schema tables) that would enable installing the DynamicFileCatalogProvider during construction

[goldmedal]

Probably a good first step would be to move the DynamicFileCatalogProvider

https://github.com/apache/datafusion/blob/088ad010a6ceaa6a2e810d418a2370e45acf3d54/datafusion-cli/src/catalog.rs#L79

into the core somewhere (but not registering it with SessionContext) Then a second step would be to add an option (like the information_schema tables) that would enable installing the DynamicFileCatalogProvider during construction

HI @alamb, I'm working on it. I think I'll create PRs for each steps.

First PR: Move to core.

After roughly surveyed, I found I need to move not only DynamicFileCatalogProvider but also something object_store-related. I plan to place

• DynamicFileCatalogProvider in datafusion/core/src/catalog
• object_store-related in datafusion/core/src/datasource/file_format

  Second PR: Add Option

  I haven't survey it. Seems I can refer to how information_schema implemented.

[edmondop]

@alamb spark SQL syntax works like so:

select * from parquet.`s3://foo-bar`

what do you think?

• I wouldn't rely on the extension, and I don't know how that works when you are querying a partitioned table (where the .parquet files are in nested folders
• if you use Parquet + a metadata format (Iceberg, Hudi, Delta) you might still have Parquet files, but a protocol layer on top of it, so one can support select * from iceberg.s3://foo-bar``

[alamb]

@edmondop I think this would be a great to add as an example / thing to implement as an extension.

[edmondop]

I wanted to confirm I understood correctly what options we are picking. It seems to me the following are viable:

1. Support "implicit" tables via select from (moving the change from datafusion-cli in core)
2. Support table functions and create a separate function for each format (read_csv, read_parquet, read_json too maybe)
3. Move formats handling to extensions?

We are taking option 1 right now, is that right @alamb ?

[alamb]

I am not quite sure what to do here to be honest

[alamb]

Update here is that @goldmedal made a PR for this issue https://github.com/apache/datafusion/pull/10745

However the initial PR brings many dependencies (like aws crates) to datafusion core that is likely not great. I had some suggestions on how we could split up the code to keep the dynamic file provider in the core whil ekeeping aws etc out: https://github.com/apache/datafusion/pull/10745#issuecomment-2175817937