feat: basic support for executing prepared statements

datafusion/core/src/execution/context/mod.rs

@@ -42,7 +42,8 @@ use crate::{
     logical_expr::{
         CreateCatalog, CreateCatalogSchema, CreateExternalTable, CreateFunction,
         CreateMemoryTable, CreateView, DropCatalogSchema, DropFunction, DropTable,
-        DropView, LogicalPlan, LogicalPlanBuilder, SetVariable, TableType, UNNAMED_TABLE,
+        DropView, Execute, LogicalPlan, LogicalPlanBuilder, Prepare, SetVariable,
+        TableType, UNNAMED_TABLE,
     },
     physical_expr::PhysicalExpr,
     physical_plan::ExecutionPlan,
@@ -54,9 +55,9 @@ use arrow::record_batch::RecordBatch;
 use arrow_schema::Schema;
 use datafusion_common::{
     config::{ConfigExtension, TableOptions},
-    exec_err, not_impl_err, plan_datafusion_err, plan_err,
+    exec_datafusion_err, exec_err, not_impl_err, plan_datafusion_err, plan_err,
     tree_node::{TreeNodeRecursion, TreeNodeVisitor},
-    DFSchema, SchemaReference, TableReference,
+    DFSchema, ParamValues, ScalarValue, SchemaReference, TableReference,
 };
 use datafusion_execution::registry::SerializerRegistry;
 use datafusion_expr::{
@@ -687,7 +688,31 @@ impl SessionContext {
             LogicalPlan::Statement(Statement::SetVariable(stmt)) => {
                 self.set_variable(stmt).await
             }
-
+            LogicalPlan::Prepare(Prepare {
+                name,
+                input,
+                data_types,
+            }) => {
+                // The number of parameters must match the specified data types length.
+                if !data_types.is_empty() {
+                    let param_names = input.get_parameter_names()?;
+                    if param_names.len() != data_types.len() {
+                        return plan_err!(
+                            "Prepare specifies {} data types but query has {} parameters",
+                            data_types.len(),
+                            param_names.len()
+                        );
+                    }
+                }
+                // Store the unoptimized plan into the session state. Although storing the
+                // optimized plan or the physical plan would be more efficient, doing so is
+                // not currently feasible. This is because `now()` would be optimized to a
+                // constant value, causing each EXECUTE to yield the same result, which is
+                // incorrect behavior.
+                self.state.write().store_prepared(name, data_types, input)?;
+                self.return_empty_dataframe()
+            }
+            LogicalPlan::Execute(execute) => self.execute_prepared(execute),
             plan => Ok(DataFrame::new(self.state(), plan)),
         }
     }
@@ -1088,6 +1113,49 @@ impl SessionContext {
         }
     }
 
+    fn execute_prepared(&self, execute: Execute) -> Result<DataFrame> {
+        let Execute {
+            name, parameters, ..
+        } = execute;
+        let prepared = self.state.read().get_prepared(&name).ok_or_else(|| {
+            exec_datafusion_err!("Prepared statement '{}' does not exist", name)
+        })?;
+
+        // Only allow literals as parameters for now.
+        let mut params: Vec<ScalarValue> = parameters
+            .into_iter()
+            .map(|e| match e {
+                Expr::Literal(scalar) => Ok(scalar),
+                _ => not_impl_err!("Unsupported data type for parameter: {}", e),
+            })
+            .collect::<Result<_>>()?;
+
+        // If the prepared statement provides data types, cast the params to those types.
+        if !prepared.data_types.is_empty() {
+            if params.len() != prepared.data_types.len() {
+                return exec_err!(
+                    "Prepared statement '{}' expects {} parameters, but {} provided",
+                    name,
+                    prepared.data_types.len(),
+                    params.len()
+                );
+            }
+            params = params
+                .into_iter()
+                .zip(prepared.data_types.iter())
+                .map(|(e, dt)| e.cast_to(dt))
+                .collect::<Result<_>>()?;
+        }
+
+        let params = ParamValues::List(params);
+        let plan = prepared
+            .plan
+            .as_ref()
+            .clone()
+            .replace_params_with_values(&params)?;
+        Ok(DataFrame::new(self.state(), plan))
+    }
+
     /// Registers a variable provider within this context.
     pub fn register_variable(
         &self,

datafusion/core/src/execution/session_state.rs

@@ -40,7 +40,7 @@ use datafusion_common::display::{PlanType, StringifiedPlan, ToStringifiedPlan};
 use datafusion_common::file_options::file_type::FileType;
 use datafusion_common::tree_node::TreeNode;
 use datafusion_common::{
-    config_err, not_impl_err, plan_datafusion_err, DFSchema, DataFusionError,
+    config_err, exec_err, not_impl_err, plan_datafusion_err, DFSchema, DataFusionError,
     ResolvedTableReference, TableReference,
 };
 use datafusion_execution::config::SessionConfig;
@@ -171,6 +171,9 @@ pub struct SessionState {
     /// It will be invoked on `CREATE FUNCTION` statements.
     /// thus, changing dialect o PostgreSql is required
     function_factory: Option<Arc<dyn FunctionFactory>>,
+    /// Cache logical plans of prepared statements for later execution.
+    /// Key is the prepared statement name.
+    prepared_plans: HashMap<String, Arc<PreparedPlan>>,
 }
 
 impl Debug for SessionState {
@@ -197,6 +200,7 @@ impl Debug for SessionState {
             .field("scalar_functions", &self.scalar_functions)
             .field("aggregate_functions", &self.aggregate_functions)
             .field("window_functions", &self.window_functions)
+            .field("prepared_plans", &self.prepared_plans)
             .finish()
     }
 }
@@ -906,6 +910,29 @@ impl SessionState {
         let udtf = self.table_functions.remove(name);
         Ok(udtf.map(|x| x.function().clone()))
     }
+
+    /// Store the logical plan and the parameter types of a prepared statement.
+    pub(crate) fn store_prepared(
+        &mut self,
+        name: String,
+        data_types: Vec<DataType>,
+        plan: Arc<LogicalPlan>,
+    ) -> datafusion_common::Result<()> {
+        match self.prepared_plans.entry(name) {
+            Entry::Vacant(e) => {
+                e.insert(Arc::new(PreparedPlan { data_types, plan }));
+                Ok(())
+            }
+            Entry::Occupied(e) => {
+                exec_err!("Prepared statement '{}' already exists", e.key())
+            }
+        }
+    }
+
+    /// Get the prepared plan with the given name.
+    pub(crate) fn get_prepared(&self, name: &str) -> Option<Arc<PreparedPlan>> {
+        self.prepared_plans.get(name).map(Arc::clone)
+    }
 }
 
 /// A builder to be used for building [`SessionState`]'s. Defaults will
@@ -1327,6 +1354,7 @@ impl SessionStateBuilder {
             table_factories: table_factories.unwrap_or_default(),
             runtime_env,
             function_factory,
+            prepared_plans: HashMap::new(),
         };
 
         if let Some(file_formats) = file_formats {
@@ -1876,6 +1904,14 @@ impl<'a> SimplifyInfo for SessionSimplifyProvider<'a> {
     }
 }
 
+#[derive(Debug)]
+pub(crate) struct PreparedPlan {
+    /// Data types of the parameters
+    pub(crate) data_types: Vec<DataType>,
+    /// The prepared logical plan
+    pub(crate) plan: Arc<LogicalPlan>,
+}
+
 #[cfg(test)]
 mod tests {
     use super::{SessionContextProvider, SessionStateBuilder};

datafusion/core/tests/sql/select.rs

@@ -57,7 +57,6 @@ async fn test_named_query_parameters() -> Result<()> {
     let ctx = create_ctx_with_partition(&tmp_dir, partition_count).await?;
 
     // sql to statement then to logical plan with parameters
-    // c1 defined as UINT32, c2 defined as UInt64
     let results = ctx
         .sql("SELECT c1, c2 FROM test WHERE c1 > $coo AND c1 < $foo")
         .await?
@@ -106,9 +105,9 @@ async fn test_prepare_statement() -> Result<()> {
     let ctx = create_ctx_with_partition(&tmp_dir, partition_count).await?;
 
     // sql to statement then to prepare logical plan with parameters
-    // c1 defined as UINT32, c2 defined as UInt64 but the params are Int32 and Float64
-    let dataframe =
-        ctx.sql("PREPARE my_plan(INT, DOUBLE) AS SELECT c1, c2 FROM test WHERE c1 > $2 AND c1 < $1").await?;
+    let dataframe = ctx
+        .sql("SELECT c1, c2 FROM test WHERE c1 > $2 AND c1 < $1")
+        .await?;
 
     // prepare logical plan to logical plan without parameters
     let param_values = vec![ScalarValue::Int32(Some(3)), ScalarValue::Float64(Some(0.0))];
@@ -156,7 +155,7 @@ async fn prepared_statement_type_coercion() -> Result<()> {
         ("unsigned", Arc::new(unsigned_ints) as ArrayRef),
     ])?;
     ctx.register_batch("test", batch)?;
-    let results = ctx.sql("PREPARE my_plan(BIGINT, INT, TEXT) AS SELECT signed, unsigned FROM test WHERE $1 >= signed AND signed <= $2 AND unsigned = $3")
+    let results = ctx.sql("SELECT signed, unsigned FROM test WHERE $1 >= signed AND signed <= $2 AND unsigned = $3")
         .await?
         .with_param_values(vec![
             ScalarValue::from(1_i64),
@@ -176,27 +175,6 @@ async fn prepared_statement_type_coercion() -> Result<()> {
     Ok(())
 }
 
-#[tokio::test]
-async fn prepared_statement_invalid_types() -> Result<()> {
-    let ctx = SessionContext::new();
-    let signed_ints: Int32Array = vec![-1, 0, 1].into();
-    let unsigned_ints: UInt64Array = vec![1, 2, 3].into();
-    let batch = RecordBatch::try_from_iter(vec![
-        ("signed", Arc::new(signed_ints) as ArrayRef),
-        ("unsigned", Arc::new(unsigned_ints) as ArrayRef),
-    ])?;
-    ctx.register_batch("test", batch)?;
-    let results = ctx
-        .sql("PREPARE my_plan(INT) AS SELECT signed FROM test WHERE signed = $1")
-        .await?
-        .with_param_values(vec![ScalarValue::from("1")]);
-    assert_eq!(
-        results.unwrap_err().strip_backtrace(),
-        "Error during planning: Expected parameter of type Int32, got Utf8 at index 0"
-    );
-    Ok(())
-}
-
 #[tokio::test]
 async fn test_parameter_type_coercion() -> Result<()> {
     let ctx = SessionContext::new();

datafusion/expr/src/logical_plan/plan.rs

@@ -1437,6 +1437,22 @@ impl LogicalPlan {
         .map(|res| res.data)
     }
 
+    /// Walk the logical plan, find any `Placeholder` tokens, and return a set of their names.
+    pub fn get_parameter_names(&self) -> Result<HashSet<String>> {
+        let mut param_names = HashSet::new();
+        self.apply_with_subqueries(|plan| {
+            plan.apply_expressions(|expr| {
+                expr.apply(|expr| {
+                    if let Expr::Placeholder(Placeholder { id, .. }) = expr {
+                        param_names.insert(id.clone());
+                    }
+                    Ok(TreeNodeRecursion::Continue)
+                })
+            })
+        })
+        .map(|_| param_names)
+    }
+
     /// Walk the logical plan, find any `Placeholder` tokens, and return a map of their IDs and DataTypes
     pub fn get_parameter_types(
         &self,