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Fix DataFrame::cache errors with Plan("Mismatch between schema and batches") #8510

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merged 4 commits into from
Dec 13, 2023
Merged

Fix DataFrame::cache errors with Plan("Mismatch between schema and batches") #8510

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bec4ccf
type cast
Asura7969 Dec 12, 2023
54c70de
add test
Asura7969 Dec 12, 2023
72c498c
use physical plan
Asura7969 Dec 13, 2023
67a84d7
logic optimization
Asura7969 Dec 13, 2023
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20 changes: 19 additions & 1 deletion datafusion/core/src/dataframe/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,8 @@ use datafusion_expr::{
};

use async_trait::async_trait;
use datafusion_optimizer::analyzer::type_coercion::TypeCoercion;
use datafusion_optimizer::analyzer::AnalyzerRule;

/// Contains options that control how data is
/// written out from a DataFrame
Expand Down Expand Up @@ -1271,8 +1273,13 @@ impl DataFrame {
/// ```
pub async fn cache(self) -> Result<DataFrame> {
let context = SessionContext::new_with_state(self.session_state.clone());
// type cast
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Rather than explcilty running (only) coercion (which is also run as part of execution) I suggest you use the schema that comes directly from the output stream

Something like (copied from Self::collect): https://docs.rs/datafusion/latest/src/datafusion/dataframe/mod.rs.html#756-760

        let task_ctx = Arc::new(self.task_ctx());
        let plan = self.create_physical_plan().await?;
        let schema = plan.schema();
        collect(plan, task_ctx).await

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Thanks for your advice

// such as, DataType::Null is normally resolved (via Coercion) to an actual type of the target schema
let analyzed_plan = TypeCoercion::new()
.analyze(self.plan.clone(), self.session_state.config_options())?;
let transform = analyzed_plan.schema().clone();
let mem_table = MemTable::try_new(
SchemaRef::from(self.schema().clone()),
SchemaRef::from(transform.as_ref().clone()),
self.collect_partitioned().await?,
)?;

Expand Down Expand Up @@ -2633,6 +2640,17 @@ mod tests {
Ok(())
}

#[tokio::test]
async fn test_cache_mismatch() -> Result<()> {
let ctx = SessionContext::new();
let df = ctx
.sql("SELECT CASE WHEN true THEN NULL ELSE 1 END")
.await?;
let cache_df = df.cache().await;
assert!(cache_df.is_ok());
Ok(())
}

#[tokio::test]
async fn cache_test() -> Result<()> {
let df = test_table()
Expand Down