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new b131cac1b0 Consolidate custom data source examples (#18142) (#18553)
b131cac1b0 is described below
commit b131cac1b0cf6ace6e250a1b32a6f210269dec13
Author: Sergey Zhukov <[email protected]>
AuthorDate: Sun Nov 9 19:48:35 2025 +0300
Consolidate custom data source examples (#18142) (#18553)
## Which issue does this PR close?
This PR is for consolidating all the `custom_data_source` examples into
a single example binary. We are agreed on the pattern and we can apply
it to the remaining examples
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enhancements and this helps us generate change logs for our releases.
You can link an issue to this PR using the GitHub syntax. For example
`Closes #123` indicates that this PR will close issue #123.
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- part of #https://github.com/apache/datafusion/issues/18142.
## Rationale for this change
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in the issue then this section is not needed.
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## What changes are included in this PR?
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## Are these changes tested?
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## Are there any user-facing changes?
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---------
Co-authored-by: Sergey Zhukov <[email protected]>
Co-authored-by: Andrew Lamb <[email protected]>
---
datafusion-examples/Cargo.toml | 4 -
datafusion-examples/README.md | 12 +-
.../examples/builtin_functions/main.rs | 5 +
.../{ => custom_data_source}/csv_json_opener.rs | 3 +-
.../{ => custom_data_source}/csv_sql_streaming.rs | 3 +-
.../{ => custom_data_source}/custom_datasource.rs | 3 +-
.../{ => custom_data_source}/custom_file_casts.rs | 4 +-
.../{ => custom_data_source}/custom_file_format.rs | 74 ++++++------
.../file_stream_provider.rs | 36 +++---
.../examples/custom_data_source/main.rs | 126 +++++++++++++++++++++
datafusion-examples/examples/flight/main.rs | 5 +
datafusion-examples/examples/udf/main.rs | 5 +
12 files changed, 210 insertions(+), 70 deletions(-)
diff --git a/datafusion-examples/Cargo.toml b/datafusion-examples/Cargo.toml
index 38f1f8b0e0..61711f8472 100644
--- a/datafusion-examples/Cargo.toml
+++ b/datafusion-examples/Cargo.toml
@@ -43,10 +43,6 @@ path = "examples/external_dependency/dataframe-to-s3.rs"
name = "query_aws_s3"
path = "examples/external_dependency/query-aws-s3.rs"
-[[example]]
-name = "custom_file_casts"
-path = "examples/custom_file_casts.rs"
-
[dev-dependencies]
arrow = { workspace = true }
# arrow_schema is required for record_batch! macro :sad:
diff --git a/datafusion-examples/README.md b/datafusion-examples/README.md
index 1befba6be6..62e51a7900 100644
--- a/datafusion-examples/README.md
+++ b/datafusion-examples/README.md
@@ -54,18 +54,18 @@ cargo run --example dataframe
- [`analyzer_rule.rs`](examples/analyzer_rule.rs): Use a custom AnalyzerRule
to change a query's semantics (row level access control)
- [`catalog.rs`](examples/catalog.rs): Register the table into a custom catalog
- [`composed_extension_codec`](examples/composed_extension_codec.rs): Example
of using multiple extension codecs for serialization / deserialization
-- [`csv_sql_streaming.rs`](examples/csv_sql_streaming.rs): Build and run a
streaming query plan from a SQL statement against a local CSV file
-- [`csv_json_opener.rs`](examples/csv_json_opener.rs): Use low level
`FileOpener` APIs to read CSV/JSON into Arrow `RecordBatch`es
-- [`custom_datasource.rs`](examples/custom_datasource.rs): Run queries against
a custom datasource (TableProvider)
-- [`custom_file_casts.rs`](examples/custom_file_casts.rs): Implement custom
casting rules to adapt file schemas
-- [`custom_file_format.rs`](examples/custom_file_format.rs): Write data to a
custom file format
+-
[`examples/custom_data_source/csv_sql_streaming.rs`](examples/custom_data_source/csv_sql_streaming.rs):
Build and run a streaming query plan from a SQL statement against a local CSV
file
+-
[`examples/custom_data_source/csv_json_opener.rs`](examples/custom_data_source/csv_json_opener.rs):
Use low level `FileOpener` APIs to read CSV/JSON into Arrow `RecordBatch`es
+-
[`examples/custom_data_source/custom_datasource.rs`](examples/custom_data_source/custom_datasource.rs):
Run queries against a custom datasource (TableProvider)
+-
[`examples/custom_data_source/custom_file_casts.rs`](examples/custom_data_source/custom_file_casts.rs):
Implement custom casting rules to adapt file schemas
+-
[`examples/custom_data_source/custom_file_format.rs`](examples/custom_data_source/custom_file_format.rs):
Write data to a custom file format
- [`dataframe-to-s3.rs`](examples/external_dependency/dataframe-to-s3.rs): Run
a query using a DataFrame against a parquet file from s3 and writing back to s3
- [`dataframe.rs`](examples/dataframe.rs): Run a query using a DataFrame API
against parquet files, csv files, and in-memory data, including multiple
subqueries. Also demonstrates the various methods to write out a DataFrame to a
table, parquet file, csv file, and json file.
-
[`examples/builtin_functions/date_time`](examples/builtin_functions/date_time.rs):
Examples of date-time related functions and queries
- [`default_column_values.rs`](examples/default_column_values.rs): Implement
custom default value handling for missing columns using field metadata and
PhysicalExprAdapter
- [`deserialize_to_struct.rs`](examples/deserialize_to_struct.rs): Convert
query results (Arrow ArrayRefs) into Rust structs
- [`expr_api.rs`](examples/expr_api.rs): Create, execute, simplify, analyze
and coerce `Expr`s
-- [`file_stream_provider.rs`](examples/file_stream_provider.rs): Run a query
on `FileStreamProvider` which implements `StreamProvider` for reading and
writing to arbitrary stream sources / sinks.
+-
[`examples/custom_data_source/file_stream_provider.rs`](examples/custom_data_source/file_stream_provider.rs):
Run a query on `FileStreamProvider` which implements `StreamProvider` for
reading and writing to arbitrary stream sources / sinks.
- [`flight/sql_server.rs`](examples/flight/sql_server.rs): Run DataFusion as a
standalone process and execute SQL queries from Flight and and FlightSQL (e.g.
JDBC) clients
-
[`examples/builtin_functions/function_factory.rs`](examples/builtin_functions/function_factory.rs):
Register `CREATE FUNCTION` handler to implement SQL macros
- [`memory_pool_tracking.rs`](examples/memory_pool_tracking.rs): Demonstrates
TrackConsumersPool for memory tracking and debugging with enhanced error
messages
diff --git a/datafusion-examples/examples/builtin_functions/main.rs
b/datafusion-examples/examples/builtin_functions/main.rs
index 3399c395bf..c307bc9532 100644
--- a/datafusion-examples/examples/builtin_functions/main.rs
+++ b/datafusion-examples/examples/builtin_functions/main.rs
@@ -19,6 +19,11 @@
//!
//! These examples demonstrate miscellaneous function-related features.
//!
+//! ## Usage
+//! ```bash
+//! cargo run --example builtin_functions --
[date_time|function_factory|regexp]
+//! ```
+//!
//! Each subcommand runs a corresponding example:
//! - `date_time` — examples of date-time related functions and queries
//! - `function_factory` — register `CREATE FUNCTION` handler to implement SQL
macros
diff --git a/datafusion-examples/examples/csv_json_opener.rs
b/datafusion-examples/examples/custom_data_source/csv_json_opener.rs
similarity index 99%
rename from datafusion-examples/examples/csv_json_opener.rs
rename to datafusion-examples/examples/custom_data_source/csv_json_opener.rs
index 6d0e4f4a3d..4205bbcdf8 100644
--- a/datafusion-examples/examples/csv_json_opener.rs
+++ b/datafusion-examples/examples/custom_data_source/csv_json_opener.rs
@@ -40,8 +40,7 @@ use object_store::{local::LocalFileSystem, memory::InMemory,
ObjectStore};
/// read data from (CSV/JSON) into Arrow RecordBatches.
///
/// If you want to query data in CSV or JSON files, see the [`dataframe.rs`]
and [`sql_query.rs`] examples
-#[tokio::main]
-async fn main() -> Result<()> {
+pub async fn csv_json_opener() -> Result<()> {
csv_opener().await?;
json_opener().await?;
Ok(())
diff --git a/datafusion-examples/examples/csv_sql_streaming.rs
b/datafusion-examples/examples/custom_data_source/csv_sql_streaming.rs
similarity index 98%
rename from datafusion-examples/examples/csv_sql_streaming.rs
rename to datafusion-examples/examples/custom_data_source/csv_sql_streaming.rs
index 99264bbcb4..aca63c4f35 100644
--- a/datafusion-examples/examples/csv_sql_streaming.rs
+++ b/datafusion-examples/examples/custom_data_source/csv_sql_streaming.rs
@@ -21,8 +21,7 @@ use datafusion::prelude::*;
/// This example demonstrates executing a simple query against an Arrow data
source (CSV) and
/// fetching results with streaming aggregation and streaming window
-#[tokio::main]
-async fn main() -> Result<()> {
+pub async fn csv_sql_streaming() -> Result<()> {
// create local execution context
let ctx = SessionContext::new();
diff --git a/datafusion-examples/examples/custom_datasource.rs
b/datafusion-examples/examples/custom_data_source/custom_datasource.rs
similarity index 99%
rename from datafusion-examples/examples/custom_datasource.rs
rename to datafusion-examples/examples/custom_data_source/custom_datasource.rs
index bc865fac5a..2213d50fcc 100644
--- a/datafusion-examples/examples/custom_datasource.rs
+++ b/datafusion-examples/examples/custom_data_source/custom_datasource.rs
@@ -42,8 +42,7 @@ use datafusion::catalog::Session;
use tokio::time::timeout;
/// This example demonstrates executing a simple query against a custom
datasource
-#[tokio::main]
-async fn main() -> Result<()> {
+pub async fn custom_datasource() -> Result<()> {
// create our custom datasource and adding some users
let db = CustomDataSource::default();
db.populate_users();
diff --git a/datafusion-examples/examples/custom_file_casts.rs
b/datafusion-examples/examples/custom_data_source/custom_file_casts.rs
similarity index 99%
rename from datafusion-examples/examples/custom_file_casts.rs
rename to datafusion-examples/examples/custom_data_source/custom_file_casts.rs
index 4d97ecd91d..31ec2845c6 100644
--- a/datafusion-examples/examples/custom_file_casts.rs
+++ b/datafusion-examples/examples/custom_data_source/custom_file_casts.rs
@@ -44,9 +44,7 @@ use object_store::{ObjectStore, PutPayload};
// This example enforces that casts must be strictly widening: if the file
type is Int64 and the table type is Int32, it will error
// before even reading the data.
// Without this custom cast rule DataFusion would happily do the narrowing
cast, potentially erroring only if it found a row with data it could not cast.
-
-#[tokio::main]
-async fn main() -> Result<()> {
+pub async fn custom_file_casts() -> Result<()> {
println!("=== Creating example data ===");
// Create a logical / table schema with an Int32 column
diff --git a/datafusion-examples/examples/custom_file_format.rs
b/datafusion-examples/examples/custom_data_source/custom_file_format.rs
similarity index 97%
rename from datafusion-examples/examples/custom_file_format.rs
rename to datafusion-examples/examples/custom_data_source/custom_file_format.rs
index 3505651eb1..510fa53c59 100644
--- a/datafusion-examples/examples/custom_file_format.rs
+++ b/datafusion-examples/examples/custom_data_source/custom_file_format.rs
@@ -48,6 +48,42 @@ use tempfile::tempdir;
/// TSVFileFormatFactory is responsible for creating instances of
TSVFileFormat.
/// The former, once registered with the SessionState, will then be used
/// to facilitate SQL operations on TSV files, such as `COPY TO` shown here.
+pub async fn custom_file_format() -> Result<()> {
+ // Create a new context with the default configuration
+ let mut state = SessionStateBuilder::new().with_default_features().build();
+
+ // Register the custom file format
+ let file_format = Arc::new(TSVFileFactory::new());
+ state.register_file_format(file_format, true)?;
+
+ // Create a new context with the custom file format
+ let ctx = SessionContext::new_with_state(state);
+
+ let mem_table = create_mem_table();
+ ctx.register_table("mem_table", mem_table)?;
+
+ let temp_dir = tempdir().unwrap();
+ let table_save_path = temp_dir.path().join("mem_table.tsv");
+
+ let d = ctx
+ .sql(&format!(
+ "COPY mem_table TO '{}' STORED AS TSV;",
+ table_save_path.display(),
+ ))
+ .await?;
+
+ let results = d.collect().await?;
+ println!(
+ "Number of inserted rows: {:?}",
+ (results[0]
+ .column_by_name("count")
+ .unwrap()
+ .as_primitive::<UInt64Type>()
+ .value(0))
+ );
+
+ Ok(())
+}
#[derive(Debug)]
/// Custom file format that reads and writes TSV files
@@ -181,44 +217,6 @@ impl GetExt for TSVFileFactory {
}
}
-#[tokio::main]
-async fn main() -> Result<()> {
- // Create a new context with the default configuration
- let mut state = SessionStateBuilder::new().with_default_features().build();
-
- // Register the custom file format
- let file_format = Arc::new(TSVFileFactory::new());
- state.register_file_format(file_format, true).unwrap();
-
- // Create a new context with the custom file format
- let ctx = SessionContext::new_with_state(state);
-
- let mem_table = create_mem_table();
- ctx.register_table("mem_table", mem_table).unwrap();
-
- let temp_dir = tempdir().unwrap();
- let table_save_path = temp_dir.path().join("mem_table.tsv");
-
- let d = ctx
- .sql(&format!(
- "COPY mem_table TO '{}' STORED AS TSV;",
- table_save_path.display(),
- ))
- .await?;
-
- let results = d.collect().await?;
- println!(
- "Number of inserted rows: {:?}",
- (results[0]
- .column_by_name("count")
- .unwrap()
- .as_primitive::<UInt64Type>()
- .value(0))
- );
-
- Ok(())
-}
-
// create a simple mem table
fn create_mem_table() -> Arc<MemTable> {
let fields = vec![
diff --git a/datafusion-examples/examples/file_stream_provider.rs
b/datafusion-examples/examples/custom_data_source/file_stream_provider.rs
similarity index 91%
rename from datafusion-examples/examples/file_stream_provider.rs
rename to
datafusion-examples/examples/custom_data_source/file_stream_provider.rs
index e6c59d57e9..55d2cc8cc0 100644
--- a/datafusion-examples/examples/file_stream_provider.rs
+++ b/datafusion-examples/examples/custom_data_source/file_stream_provider.rs
@@ -15,6 +15,29 @@
// specific language governing permissions and limitations
// under the License.
+/// Demonstrates how to use [`FileStreamProvider`] and [`StreamTable`] to
stream data
+/// from a file-like source (FIFO) into DataFusion for continuous querying.
+///
+/// On non-Windows systems, this example creates a named pipe (FIFO) and
+/// writes rows into it asynchronously while DataFusion reads the data
+/// through a `FileStreamProvider`.
+///
+/// This illustrates how to integrate dynamically updated data sources
+/// with DataFusion without needing to reload the entire dataset each time.
+///
+/// This example does not work on Windows.
+pub async fn file_stream_provider() -> datafusion::error::Result<()> {
+ #[cfg(target_os = "windows")]
+ {
+ println!("file_stream_provider example does not work on windows");
+ Ok(())
+ }
+ #[cfg(not(target_os = "windows"))]
+ {
+ non_windows::main().await
+ }
+}
+
#[cfg(not(target_os = "windows"))]
mod non_windows {
use datafusion::assert_batches_eq;
@@ -186,16 +209,3 @@ mod non_windows {
Ok(())
}
}
-
-#[tokio::main]
-async fn main() -> datafusion::error::Result<()> {
- #[cfg(target_os = "windows")]
- {
- println!("file_stream_provider example does not work on windows");
- Ok(())
- }
- #[cfg(not(target_os = "windows"))]
- {
- non_windows::main().await
- }
-}
diff --git a/datafusion-examples/examples/custom_data_source/main.rs
b/datafusion-examples/examples/custom_data_source/main.rs
new file mode 100644
index 0000000000..ce0585f8c3
--- /dev/null
+++ b/datafusion-examples/examples/custom_data_source/main.rs
@@ -0,0 +1,126 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! # These examples are all related to extending or defining how DataFusion
reads data
+//!
+//! These examples demonstrate how DataFusion reads data.
+//!
+//! ## Usage
+//! ```bash
+//! cargo run --example custom_data_source --
[csv_json_opener|csv_sql_streaming|custom_datasource|custom_file_casts|custom_file_format|file_stream_provider]
+//! ```
+//!
+//! Each subcommand runs a corresponding example:
+//! - `csv_json_opener` — use low level FileOpener APIs to read CSV/JSON into
Arrow RecordBatches
+//! - `csv_sql_streaming` — build and run a streaming query plan from a SQL
statement against a local CSV file
+//! - `custom_datasource` — run queries against a custom datasource
(TableProvider)
+//! - `custom_file_casts` — implement custom casting rules to adapt file
schemas
+//! - `custom_file_format` — write data to a custom file format
+//! - `file_stream_provider` — run a query on FileStreamProvider which
implements StreamProvider for reading and writing to arbitrary stream
sources/sinks
+
+mod csv_json_opener;
+mod csv_sql_streaming;
+mod custom_datasource;
+mod custom_file_casts;
+mod custom_file_format;
+mod file_stream_provider;
+
+use std::str::FromStr;
+
+use datafusion::error::{DataFusionError, Result};
+
+enum ExampleKind {
+ CsvJsonOpener,
+ CsvSqlStreaming,
+ CustomDatasource,
+ CustomFileCasts,
+ CustomFileFormat,
+ FileFtreamProvider,
+}
+
+impl AsRef<str> for ExampleKind {
+ fn as_ref(&self) -> &str {
+ match self {
+ Self::CsvJsonOpener => "csv_json_opener",
+ Self::CsvSqlStreaming => "csv_sql_streaming",
+ Self::CustomDatasource => "custom_datasource",
+ Self::CustomFileCasts => "custom_file_casts",
+ Self::CustomFileFormat => "custom_file_format",
+ Self::FileFtreamProvider => "file_stream_provider",
+ }
+ }
+}
+
+impl FromStr for ExampleKind {
+ type Err = DataFusionError;
+
+ fn from_str(s: &str) -> Result<Self> {
+ match s {
+ "csv_json_opener" => Ok(Self::CsvJsonOpener),
+ "csv_sql_streaming" => Ok(Self::CsvSqlStreaming),
+ "custom_datasource" => Ok(Self::CustomDatasource),
+ "custom_file_casts" => Ok(Self::CustomFileCasts),
+ "custom_file_format" => Ok(Self::CustomFileFormat),
+ "file_stream_provider" => Ok(Self::FileFtreamProvider),
+ _ => Err(DataFusionError::Execution(format!("Unknown example:
{s}"))),
+ }
+ }
+}
+
+impl ExampleKind {
+ const ALL: [Self; 6] = [
+ Self::CsvJsonOpener,
+ Self::CsvSqlStreaming,
+ Self::CustomDatasource,
+ Self::CustomFileCasts,
+ Self::CustomFileFormat,
+ Self::FileFtreamProvider,
+ ];
+
+ const EXAMPLE_NAME: &str = "custom_data_source";
+
+ fn variants() -> Vec<&'static str> {
+ Self::ALL.iter().map(|x| x.as_ref()).collect()
+ }
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+ let usage = format!(
+ "Usage: cargo run --example {} -- [{}]",
+ ExampleKind::EXAMPLE_NAME,
+ ExampleKind::variants().join("|")
+ );
+
+ let arg = std::env::args().nth(1).ok_or_else(|| {
+ eprintln!("{usage}");
+ DataFusionError::Execution("Missing argument".to_string())
+ })?;
+
+ match arg.parse::<ExampleKind>()? {
+ ExampleKind::CsvJsonOpener =>
csv_json_opener::csv_json_opener().await?,
+ ExampleKind::CsvSqlStreaming =>
csv_sql_streaming::csv_sql_streaming().await?,
+ ExampleKind::CustomDatasource =>
custom_datasource::custom_datasource().await?,
+ ExampleKind::CustomFileCasts =>
custom_file_casts::custom_file_casts().await?,
+ ExampleKind::CustomFileFormat =>
custom_file_format::custom_file_format().await?,
+ ExampleKind::FileFtreamProvider => {
+ file_stream_provider::file_stream_provider().await?
+ }
+ }
+
+ Ok(())
+}
diff --git a/datafusion-examples/examples/flight/main.rs
b/datafusion-examples/examples/flight/main.rs
index a448789b35..a83b19bac4 100644
--- a/datafusion-examples/examples/flight/main.rs
+++ b/datafusion-examples/examples/flight/main.rs
@@ -19,6 +19,11 @@
//!
//! These examples demonstrate Arrow Flight usage.
//!
+//! ## Usage
+//! ```bash
+//! cargo run --example flight -- [client|server|sql_server]
+//! ```
+//!
//! Each subcommand runs a corresponding example:
//! - `client` — run DataFusion as a standalone process and execute SQL
queries from a client using the Flight protocol
//! - `server` — run DataFusion as a standalone process and execute SQL
queries from a client using the Flight protocol
diff --git a/datafusion-examples/examples/udf/main.rs
b/datafusion-examples/examples/udf/main.rs
index ba36dbb15c..104d373937 100644
--- a/datafusion-examples/examples/udf/main.rs
+++ b/datafusion-examples/examples/udf/main.rs
@@ -19,6 +19,11 @@
//!
//! These examples demonstrate user-defined functions in DataFusion.
//!
+//! ## Usage
+//! ```bash
+//! cargo run --example udf --
[adv_udaf|adv_udf|adv_udwf|async_udf|udaf|udf|udtf|udwf]
+//! ```
+//!
//! Each subcommand runs a corresponding example:
//! - `adv_udaf` — user defined aggregate function example
//! - `adv_udf` — user defined scalar function example
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