martin-g commented on code in PR #20222:
URL: https://github.com/apache/datafusion/pull/20222#discussion_r2781680944
##########
datafusion-examples/examples/udf/main.rs:
##########
Review Comment:
```suggestion
//! (file: simple_udwf.rs, desc: Simple UDWF example)
//!
//! - `table_list_udtf`
//! (file: table_list_udtf.rs, desc: Session-aware UDTF table list example)
```
##########
datafusion/ffi/src/udtf.rs:
##########
@@ -43,11 +45,18 @@ use crate::{df_result, rresult_return};
#[repr(C)]
#[derive(Debug, StableAbi)]
pub struct FFI_TableFunction {
- /// Equivalent to the `call` function of the TableFunctionImpl.
+ /// Equivalent to the [`TableFunctionImpl::call`].
/// The arguments are Expr passed as protobuf encoded bytes.
pub call:
unsafe extern "C" fn(udtf: &Self, args: RVec<u8>) ->
FFIResult<FFI_TableProvider>,
+ /// Equivalent to the [`TableFunctionImpl::call_with_args`].
+ call_with_args: unsafe extern "C" fn(
Review Comment:
The `call` field above is `pub`. Is it intentional that `call_with_args` is
private ?
##########
datafusion-examples/examples/udf/table_list_udtf.rs:
##########
@@ -0,0 +1,125 @@
+// 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.
+
+//! See `main.rs` for how to run it.
+
+use std::sync::{Arc, LazyLock};
+
+use arrow::array::{RecordBatch, StringArray};
+use arrow_schema::{DataType, Field, Schema, SchemaRef};
+use datafusion::{
+ catalog::{MemTable, TableFunctionArgs, TableFunctionImpl, TableProvider},
+ common::Result,
+ execution::SessionState,
+ prelude::SessionContext,
+};
+use datafusion_common::{DataFusionError, plan_err};
+use futures::executor::block_on;
+
+const FUNCTION_NAME: &str = "table_list";
+
+// The example shows, how to create UDTF that depends on the session state.
+// There is `table_list` UDTF is defined which returns list of tables within
session.
+
+pub async fn table_list_udtf() -> Result<()> {
+ let ctx = SessionContext::new();
+ ctx.register_udtf(FUNCTION_NAME, Arc::new(TableListUdtf));
+
+ // Register different kinds of tables.
+ ctx.sql("create view v as select 1")
+ .await?
+ .collect()
+ .await?;
+ ctx.sql("create table t(a int)").await?.collect().await?;
+
+ // Print results.
+ ctx.sql("select * from table_list()").await?.show().await?;
+
+ Ok(())
+}
+
+#[derive(Debug, Default)]
+struct TableListUdtf;
+
+static SCHEMA: LazyLock<SchemaRef> = LazyLock::new(|| {
+ SchemaRef::new(Schema::new(vec![
+ Field::new("catalog", DataType::Utf8, false),
+ Field::new("schema", DataType::Utf8, false),
+ Field::new("table", DataType::Utf8, false),
+ Field::new("type", DataType::Utf8, false),
+ ]))
+});
+
+impl TableFunctionImpl for TableListUdtf {
+ fn call_with_args(&self, args: TableFunctionArgs) -> Result<Arc<dyn
TableProvider>> {
+ if !args.args.is_empty() {
+ return plan_err!(
+ "{}: unexpected number of arguments: {}, expected: 0",
+ FUNCTION_NAME,
+ args.args.len()
+ );
+ }
+ let state = args
+ .session
+ .as_any()
+ .downcast_ref::<SessionState>()
+ .ok_or_else(|| {
+ DataFusionError::Internal("failed to downcast state".into())
+ })?;
+
+ let mut catalogs = vec![];
+ let mut schemas = vec![];
+ let mut tables = vec![];
+ let mut types = vec![];
+
+ let catalog_list = state.catalog_list();
+ for catalog_name in catalog_list.catalog_names() {
+ let Some(catalog) = catalog_list.catalog(&catalog_name) else {
+ continue;
+ };
+ for schema_name in catalog.schema_names() {
+ let Some(schema) = catalog.schema(&schema_name) else {
+ continue;
+ };
+ for table_name in schema.table_names() {
+ let Some(provider) = block_on(schema.table(&table_name))?
else {
Review Comment:
The example is executed inside Tokio runtime
(https://github.com/apache/datafusion/pull/20222/changes#diff-53dddc5b69b35049efec032575318a260c5538e27cef966ffe2e634c41d5e949R113),
so it will be better to use `Handle::current().block_on()` instead.
See https://docs.rs/tokio/latest/tokio/task/fn.block_in_place.html for an
example
##########
datafusion-examples/examples/udf/table_list_udtf.rs:
##########
@@ -0,0 +1,125 @@
+// 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.
+
+//! See `main.rs` for how to run it.
+
+use std::sync::{Arc, LazyLock};
+
+use arrow::array::{RecordBatch, StringArray};
+use arrow_schema::{DataType, Field, Schema, SchemaRef};
+use datafusion::{
+ catalog::{MemTable, TableFunctionArgs, TableFunctionImpl, TableProvider},
+ common::Result,
+ execution::SessionState,
+ prelude::SessionContext,
+};
+use datafusion_common::{DataFusionError, plan_err};
+use futures::executor::block_on;
+
+const FUNCTION_NAME: &str = "table_list";
+
+// The example shows, how to create UDTF that depends on the session state.
+// There is `table_list` UDTF is defined which returns list of tables within
session.
Review Comment:
```suggestion
// Defines a `table_list` UDTF that returns a list of tables within the
provided session.
```
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