20222: Provide session to the udtf call #296
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,128 @@ | ||
| // 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. | ||
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| //! See `main.rs` for how to run it. | ||
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| use std::sync::{Arc, LazyLock}; | ||
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| use arrow::array::{RecordBatch, StringBuilder}; | ||
| 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 tokio::{runtime::Handle, task::block_in_place}; | ||
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| const FUNCTION_NAME: &str = "table_list"; | ||
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| // The example shows, how to create UDTF that depends on the session state. | ||
| // Defines a `table_list` UDTF that returns a list of tables within the provided session. | ||
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| pub async fn table_list_udtf() -> Result<()> { | ||
| let ctx = SessionContext::new(); | ||
| ctx.register_udtf(FUNCTION_NAME, Arc::new(TableListUdtf)); | ||
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| // 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?; | ||
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| // Print results. | ||
| ctx.sql("select * from table_list()").await?.show().await?; | ||
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| Ok(()) | ||
| } | ||
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| #[derive(Debug, Default)] | ||
| struct TableListUdtf; | ||
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| 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), | ||
| ])) | ||
| }); | ||
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| 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()) | ||
| })?; | ||
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| let mut catalogs = StringBuilder::new(); | ||
| let mut schemas = StringBuilder::new(); | ||
| let mut tables = StringBuilder::new(); | ||
| let mut types = StringBuilder::new(); | ||
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| 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_in_place(|| { | ||
| Handle::current().block_on(schema.table(&table_name)) | ||
| })? | ||
| else { | ||
| continue; | ||
| }; | ||
| catalogs.append_value(catalog_name.clone()); | ||
| schemas.append_value(schema_name.clone()); | ||
| tables.append_value(table_name.clone()); | ||
| types.append_value(provider.table_type().to_string()) | ||
| } | ||
| } | ||
| } | ||
|
Comment on lines
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There was a problem hiding this comment. The current implementation iterates through catalogs, schemas, and tables, and for each table, it blocks to get the table provider. Using To improve performance, you could gather all the asynchronous let mut table_futures = vec![];
for catalog_name in catalog_list.catalog_names() {
if let Some(catalog) = catalog_list.catalog(&catalog_name) {
for schema_name in catalog.schema_names() {
if let Some(schema) = catalog.schema(&schema_name) {
for table_name in schema.table_names() {
let schema_clone = Arc::clone(&schema);
let catalog_name_clone = catalog_name.clone();
let schema_name_clone = schema_name.clone();
let table_name_clone = table_name.clone();
table_futures.push(async move {
schema_clone.table(&table_name_clone).await.map(|provider| {
(catalog_name_clone, schema_name_clone, table_name_clone, provider)
})
});
}
}
}
}
}
let results = block_in_place(|| {
Handle::current().block_on(futures::future::try_join_all(table_futures))
})?;
for (catalog_name, schema_name, table_name, provider) in results {
if let Some(provider) = provider {
catalogs.append_value(catalog_name);
schemas.append_value(schema_name);
tables.append_value(table_name);
types.append_value(provider.table_type().to_string())
}
}
Owner
Author
There was a problem hiding this comment. value:good-to-have; category:bug; feedback: The Gemini AI reviewer is correct! The current solution uses Tokio's |
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| let batch = RecordBatch::try_new( | ||
| Arc::clone(&SCHEMA), | ||
| vec![ | ||
| Arc::new(catalogs.finish()), | ||
| Arc::new(schemas.finish()), | ||
| Arc::new(tables.finish()), | ||
| Arc::new(types.finish()), | ||
| ], | ||
| )?; | ||
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| Ok(Arc::new(MemTable::try_new( | ||
| batch.schema(), | ||
| vec![vec![batch]], | ||
| )?)) | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -1830,6 +1830,8 @@ impl ContextProvider for SessionContextProvider<'_> { | |
| name: &str, | ||
| args: Vec<Expr>, | ||
| ) -> datafusion_common::Result<Arc<dyn TableSource>> { | ||
| use datafusion_catalog::TableFunctionArgs; | ||
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| let tbl_func = self | ||
| .state | ||
| .table_functions | ||
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@@ -1852,7 +1854,10 @@ impl ContextProvider for SessionContextProvider<'_> { | |
| .and_then(|e| simplifier.simplify(e)) | ||
| }) | ||
| .collect::<datafusion_common::Result<Vec<_>>>()?; | ||
| let provider = tbl_func.create_table_provider_with_args(TableFunctionArgs { | ||
| args: &args, | ||
| session: self.state, | ||
| })?; | ||
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| Ok(provider_as_source(provider)) | ||
| } | ||
|
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -33,8 +33,8 @@ use datafusion::error::Result; | |
| use datafusion::execution::TaskContext; | ||
| use datafusion::physical_plan::{ExecutionPlan, collect}; | ||
| use datafusion::prelude::SessionContext; | ||
| use datafusion_catalog::TableFunctionImpl; | ||
| use datafusion_catalog::{Session, TableFunctionArgs}; | ||
| use datafusion_common::{DFSchema, ScalarValue}; | ||
| use datafusion_expr::{EmptyRelation, Expr, LogicalPlan, Projection, TableType}; | ||
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@@ -200,7 +200,8 @@ impl SimpleCsvTable { | |
| struct SimpleCsvTableFunc {} | ||
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| impl TableFunctionImpl for SimpleCsvTableFunc { | ||
| fn call_with_args(&self, args: TableFunctionArgs) -> Result<Arc<dyn TableProvider>> { | ||
| let exprs = args.args; | ||
| let mut new_exprs = vec![]; | ||
| let mut filepath = String::new(); | ||
| for expr in exprs { | ||
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@@ -231,7 +232,7 @@ async fn test_udtf_type_coercion() -> Result<()> { | |
| struct NoOpTableFunc; | ||
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| impl TableFunctionImpl for NoOpTableFunc { | ||
| fn call_with_args(&self, _: TableFunctionArgs) -> Result<Arc<dyn TableProvider>> { | ||
| let schema = Arc::new(arrow::datatypes::Schema::empty()); | ||
| Ok(Arc::new(MemTable::try_new(schema, vec![vec![]])?)) | ||
| } | ||
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datafusion-examples/examples/udf/table_list_udtf.rs:100: Usingblock_in_place+Handle::current().block_on(...)will panic iftable_list()is invoked without a Tokio runtime, andblock_in_placealso requires the multi-thread runtime. Since UDTFs can be called from various execution contexts, it may be worth documenting/guarding these runtime assumptions for the example.Severity: medium
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value:good-to-have; category:documentation; feedback: The Augment AI reviewer is correct! The example would work only in multi-threaded Tokio runtime. It would be good to document this (e.g. with a comment), so the users copying this example into their application are aware of this limitation.