clickhouse-datafusion 0.2.0

//! Core helpers for adapting a [`SessionContext`] to `ClickHouse` semantics.
//! The types defined here keep ClickHouse-specific UDFs, query planners, and
//! optimiser rules intact while still exposing DataFusion’s familiar APIs.
//! [`ClickHouseQueryPlanner`] can be stacked with additional extension planners,
//! while [`ClickHouseSessionContext`] ensures the rebuilt session keeps remote
//! pushdown logic, custom UDFs, and any caller-provided configuration.
pub mod plan_node;
pub mod planner;

use std::collections::HashMap;
use std::collections::hash_map::Entry;
use std::sync::Arc;

use async_trait::async_trait;
use datafusion::arrow::datatypes::{DataType, SchemaRef};
use datafusion::catalog::cte_worktable::CteWorkTable;
use datafusion::common::file_options::file_type::FileType;
use datafusion::common::plan_datafusion_err;
use datafusion::config::{ConfigOptions, Dialect};
use datafusion::datasource::file_format::format_as_file_type;
use datafusion::datasource::provider_as_source;
use datafusion::error::Result;
use datafusion::execution::SessionState;
use datafusion::execution::context::QueryPlanner;
use datafusion::logical_expr::planner::{ExprPlanner, TypePlanner};
use datafusion::logical_expr::var_provider::is_system_variables;
use datafusion::logical_expr::{AggregateUDF, LogicalPlan, ScalarUDF, TableSource, WindowUDF};
use datafusion::optimizer::AnalyzerRule;
use datafusion::optimizer::analyzer::type_coercion::TypeCoercion;
use datafusion::physical_plan::ExecutionPlan;
use datafusion::physical_planner::{DefaultPhysicalPlanner, ExtensionPlanner, PhysicalPlanner};
use datafusion::prelude::{DataFrame, Expr, SQLOptions, SessionContext};
use datafusion::sql::parser::Statement;
use datafusion::sql::planner::{ContextProvider, NullOrdering, ParserOptions, SqlToRel};
use datafusion::sql::{ResolvedTableReference, TableReference};
use datafusion::variable::VarType;

use self::planner::ClickHouseExtensionPlanner;
use crate::analyzer::function_pushdown::ClickHouseFunctionPushdown;
use crate::udfs::apply::{CLICKHOUSE_APPLY_ALIASES, clickhouse_apply_udf};
use crate::udfs::clickhouse::{CLICKHOUSE_UDF_ALIASES, clickhouse_udf};
use crate::udfs::placeholder::PlaceholderUDF;

/// Convenience method (opinionated) for preparing a session context both with federation if the
/// feature is enabled as well as UDF pushdown support through the custom `Analyzer`. It is called
/// in [`ClickHouseSessionContext::new`] and [`ClickHouseSessionContext::from`] when creating a new
/// [`ClickHouseSessionContext`].
///
/// NOTE: The setting `enable_ident_normalization` is enabled by default, but `ClickHouse` idents
/// are case-sensitive. It's important to note this settings does NOT correct the problem where
/// function names are normalized to lowercase, so backticks are still needed.
///
/// See: [`datafusion.sql_parser.enable_ident_normalization`](https://datafusion.apache.org/user-guide/configs.html)
pub fn prepare_session_context(
    ctx: SessionContext,
    extension_planners: Option<Vec<Arc<dyn ExtensionPlanner + Send + Sync>>>,
) -> SessionContext {
    #[cfg(feature = "federation")]
    use crate::federation::FederatedContext as _;

    // If federation is enabled, federate the context first. The planners will be overridden to
    // still include the FederatedQueryPlanner, this just saves a step with the optimizer
    #[cfg(feature = "federation")]
    let ctx = ctx.federate();
    // Pull out state
    let state = ctx.state();
    let config = state.config().clone();
    // NOTE: ClickHouse identifiers are case-sensitive. We keep DataFusion's
    // default normalisation behaviour for now; once ClickHouse functions can
    // opt in explicitly we can revisit toggling the parser option here.
    // let config = if config.options().sql_parser.enable_ident_normalization {
    //     config.set_bool("datafusion.sql_parser.enable_ident_normalization", false)
    // } else {
    //     config
    // };
    let config = config.set_str("datafusion.sql_parser.dialect", "ClickHouse");
    // Pushdown analyzer rule
    let state_builder = if state
        .analyzer()
        .rules
        .iter()
        .any(|rule| rule.name() == ClickHouseFunctionPushdown.name())
    {
        ctx.into_state_builder()
    } else {
        let analyzer_rules = configure_analyzer_rules(&state);
        ctx.into_state_builder().with_analyzer_rules(analyzer_rules)
    };
    // Finally, build the context again passing the ClickHouseQueryPlanner
    let ctx = SessionContext::new_with_state(
        state_builder
            .with_config(config)
            .with_query_planner(Arc::new(ClickHouseQueryPlanner::new_with_planners(
                extension_planners.unwrap_or_default(),
            )))
            .build(),
    );
    ctx.register_udf(clickhouse_udf());
    ctx.register_udf(clickhouse_apply_udf());
    ctx
}

/// Given a `SessionState`, configure the analyzer rules for the `ClickHouse` session context.
pub fn configure_analyzer_rules(state: &SessionState) -> Vec<Arc<dyn AnalyzerRule + Send + Sync>> {
    // Pull out analyzer rules
    let mut analyzer_rules = state.analyzer().rules.clone();

    // Insert the ClickHouseFunctionPushdown before type coercion.
    // This allows datafusion to optimize for the data types expected.
    let type_coercion = TypeCoercion::default();
    let pos = analyzer_rules.iter().position(|x| x.name() == type_coercion.name()).unwrap_or(0);

    let pushdown_rule = Arc::new(ClickHouseFunctionPushdown);
    analyzer_rules.insert(pos, pushdown_rule);
    analyzer_rules
}

/// A custom `QueryPlanner` leveraging [`ClickHouseExtensionPlanner`]
#[derive(Clone)]
pub struct ClickHouseQueryPlanner {
    planners: Vec<Arc<dyn ExtensionPlanner + Send + Sync>>,
}

impl std::fmt::Debug for ClickHouseQueryPlanner {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ClickHouseQueryPlanner").finish()
    }
}

impl Default for ClickHouseQueryPlanner {
    fn default() -> Self { Self::new() }
}

impl ClickHouseQueryPlanner {
    /// Construct a planner pre-loaded with the `ClickHouse` extension planner
    /// (and the federation planner when that feature is enabled).
    pub fn new() -> Self {
        let planners = vec![
            #[cfg(feature = "federation")]
            Arc::new(datafusion_federation::FederatedPlanner::new()),
            Arc::new(ClickHouseExtensionPlanner {}) as Arc<dyn ExtensionPlanner + Send + Sync>,
        ];
        ClickHouseQueryPlanner { planners }
    }

    /// Construct a planner and append additional extension planners provided
    /// by the caller.  These planners execute after the built-in `ClickHouse`
    /// extensions.
    pub fn new_with_planners(planners: Vec<Arc<dyn ExtensionPlanner + Send + Sync>>) -> Self {
        let mut this = Self::new();
        this.planners.extend(planners);
        this
    }

    /// Append a single extension planner to an existing `ClickHouseQueryPlanner`.
    #[must_use]
    pub fn with_planner(mut self, planner: Arc<dyn ExtensionPlanner + Send + Sync>) -> Self {
        self.planners.push(planner);
        self
    }
}

#[async_trait]
impl QueryPlanner for ClickHouseQueryPlanner {
    async fn create_physical_plan(
        &self,
        logical_plan: &LogicalPlan,
        session_state: &SessionState,
    ) -> Result<Arc<dyn ExecutionPlan>> {
        // Delegate to DefaultQueryPlanner with custom extension planners
        let planner = DefaultPhysicalPlanner::with_extension_planners(self.planners.clone());
        planner.create_physical_plan(logical_plan, session_state).await
    }
}

/// Wrapper for [`SessionContext`] which allows running arbitrary `ClickHouse` functions.
///
/// The wrapper rebuilds the supplied `SessionContext` with ClickHouse-specific
/// optimisers, query planner extensions, and registered UDFs. If your application
/// had additional session customisations (for example custom catalogs, URL-table
/// support, or runtime configuration) call [`ClickHouseSessionContext::with_session_transform`]
/// to re-apply them after construction.
#[derive(Clone)]
pub struct ClickHouseSessionContext {
    inner:        SessionContext,
    expr_planner: Option<Arc<dyn ExprPlanner>>,
}

impl ClickHouseSessionContext {
    /// Wrap a [`SessionContext`] with ClickHouse-specific planners and analyser rules.
    ///
    /// Optional extension planners can be provided to further customise physical
    /// planning.  Any additional configuration can be re-applied later via
    /// [`with_session_transform`](Self::with_session_transform).
    pub fn new(
        ctx: SessionContext,
        extension_planners: Option<Vec<Arc<dyn ExtensionPlanner + Send + Sync>>>,
    ) -> Self {
        Self { inner: prepare_session_context(ctx, extension_planners), expr_planner: None }
    }

    #[must_use]
    pub fn with_expr_planner(mut self, expr_planner: Arc<dyn ExprPlanner>) -> Self {
        self.expr_planner = Some(expr_planner);
        self
    }

    /// Apply a caller-provided transformation to the underlying [`SessionContext`].
    ///
    /// This is useful when existing configuration needs to be preserved across the
    /// internal context rebuild performed by [`ClickHouseSessionContext`]. For example,
    /// consumers that enabled features such as `SessionContext::enable_url_table`
    /// prior to constructing the wrapper can re-apply that configuration via:
    ///
    /// ```rust,ignore
    /// # use datafusion::prelude::*;
    /// # use clickhouse_datafusion::ClickHouseSessionContext;
    /// let base = SessionContext::new();
    /// let clickhouse_ctx = ClickHouseSessionContext::from(base)
    ///     .with_session_transform(|ctx| ctx.enable_url_table());
    /// ```
    ///
    /// The provided closure consumes the current `SessionContext` and must return
    /// a (potentially modified) instance. The ClickHouse-specific configuration,
    /// such as registered UDFs and custom planners, remains intact.
    #[must_use]
    pub fn with_session_transform<F>(mut self, transform: F) -> Self
    where
        F: FnOnce(SessionContext) -> SessionContext,
    {
        self.inner = transform(self.inner);
        self
    }

    /// Access the underlying session context by reference.
    pub fn session_context(&self) -> &SessionContext { &self.inner }

    /// Consume the wrapper and return the underlying [`SessionContext`].
    ///
    /// This bypasses the `ClickHouse` convenience APIs; further calls must ensure
    /// pushdown-related configuration stays consistent.
    pub fn into_session_context(self) -> SessionContext { self.inner }

    /// Execute SQL using the ClickHouse-aware session (see [`SessionContext::sql`]).
    /// # Errors
    ///
    /// Returns an error if the SQL query is invalid or if the query execution fails.
    pub async fn sql(&self, sql: &str) -> Result<DataFrame> {
        self.sql_with_options(sql, SQLOptions::new()).await
    }

    /// Execute SQL with custom [`SQLOptions`] using the ClickHouse-aware session.
    /// # Errors
    ///
    /// Returns an error if the SQL query is invalid or if the query execution fails.
    pub async fn sql_with_options(&self, sql: &str, options: SQLOptions) -> Result<DataFrame> {
        let state = self.inner.state();
        let statement = state.sql_to_statement(sql, &Dialect::ClickHouse)?;
        let plan = self.statement_to_plan(&state, statement).await?;
        options.verify_plan(&plan)?;
        self.execute_logical_plan(plan).await
    }

    /// Convert a SQL statement into a logical plan using ClickHouse-specific resolution.
    ///
    /// This mirrors [`SessionContext::statement_to_plan`] while routing table and
    /// function resolution through [`ClickHouseContextProvider`] so `ClickHouse` UDFs
    /// and remote catalog entries remain accessible.
    /// # Errors
    /// - Returns an error if the SQL query is invalid or if the query execution fails.
    pub async fn statement_to_plan(
        &self,
        state: &SessionState,
        statement: Statement,
    ) -> Result<LogicalPlan> {
        let references = state.resolve_table_references(&statement)?;

        let provider =
            ClickHouseContextProvider::new(state.clone(), HashMap::with_capacity(references.len()));

        let mut provider = if let Some(planner) = self.expr_planner.as_ref() {
            provider.with_expr_planner(Arc::clone(planner))
        } else {
            provider
        };

        for reference in references {
            // Recreate DataFusion's internal resolution so ClickHouse tables that
            // are not yet registered locally can be discovered on demand.
            let catalog = &state.config_options().catalog;
            let resolved = reference.resolve(&catalog.default_catalog, &catalog.default_schema);
            if let Entry::Vacant(v) = provider.tables.entry(resolved) {
                let resolved = v.key();
                if let Ok(schema) = provider.state.schema_for_ref(resolved.clone())
                    && let Some(table) = schema.table(&resolved.table).await?
                {
                    let _ = v.insert(provider_as_source(table));
                }
            }
        }

        SqlToRel::new_with_options(&provider, Self::get_parser_options(&self.state()))
            .statement_to_plan(statement)
    }

    fn get_parser_options(state: &SessionState) -> ParserOptions {
        let sql_parser_options = &state.config().options().sql_parser;
        ParserOptions {
            parse_float_as_decimal:             sql_parser_options.parse_float_as_decimal,
            enable_ident_normalization:         sql_parser_options.enable_ident_normalization,
            enable_options_value_normalization: sql_parser_options
                .enable_options_value_normalization,
            support_varchar_with_length:        sql_parser_options.support_varchar_with_length,
            map_string_types_to_utf8view:       sql_parser_options.map_string_types_to_utf8view,
            collect_spans:                      sql_parser_options.collect_spans,
            default_null_ordering:              NullOrdering::NullsMax,
        }
    }
}

impl From<SessionContext> for ClickHouseSessionContext {
    fn from(inner: SessionContext) -> Self { Self::new(inner, None) }
}

impl From<&SessionContext> for ClickHouseSessionContext {
    fn from(inner: &SessionContext) -> Self { Self::new(inner.clone(), None) }
}

impl std::ops::Deref for ClickHouseSessionContext {
    type Target = SessionContext;

    fn deref(&self) -> &Self::Target { &self.inner }
}

/// Custom [`ContextProvider`]
///
/// Required since `DataFusion` will throw an error on unrecognized functions and the goal is to
/// preserve the Expr structure.
pub struct ClickHouseContextProvider {
    state:         SessionState,
    tables:        HashMap<ResolvedTableReference, Arc<dyn TableSource>>,
    expr_planners: Vec<Arc<dyn ExprPlanner>>,
    type_planner:  Option<Arc<dyn TypePlanner>>,
}

impl ClickHouseContextProvider {
    pub fn new(
        state: SessionState,
        tables: HashMap<ResolvedTableReference, Arc<dyn TableSource>>,
    ) -> Self {
        Self { state, tables, expr_planners: vec![], type_planner: None }
    }

    #[must_use]
    pub fn with_expr_planner(mut self, planner: Arc<dyn ExprPlanner>) -> Self {
        self.expr_planners.push(planner);
        self
    }

    #[must_use]
    pub fn with_type_planner(mut self, type_planner: Arc<dyn TypePlanner>) -> Self {
        self.type_planner = Some(type_planner);
        self
    }

    /// NOTE: This method normally resides on `SessionState` but since it's `pub(crate)` it must be
    /// reproduced here.
    fn resolve_table_ref(&self, table_ref: impl Into<TableReference>) -> ResolvedTableReference {
        let catalog = &self.state.config_options().catalog;
        table_ref.into().resolve(&catalog.default_catalog, &catalog.default_schema)
    }
}

impl ContextProvider for ClickHouseContextProvider {
    fn get_function_meta(&self, name: &str) -> Option<Arc<ScalarUDF>> {
        // Early exit for clickhouse pushdown
        if CLICKHOUSE_UDF_ALIASES.contains(&name) {
            return Some(Arc::new(clickhouse_udf()));
        }

        // Early exit for clickhouse apply
        if CLICKHOUSE_APPLY_ALIASES.contains(&name) {
            return Some(Arc::new(clickhouse_apply_udf()));
        }

        // Delegate to inner provider for other UDFs
        if let Some(func) = self.state.scalar_functions().get(name) {
            return Some(Arc::clone(func));
        }

        // Check if this is a known aggregate or window function
        // These should NOT be wrapped as placeholder UDFs
        if self.state.aggregate_functions().contains_key(name) {
            return None;
        }
        if self.state.window_functions().contains_key(name) {
            return None;
        }

        // Allow inner functions to parse as placeholder ScalarUDFs
        Some(Arc::new(ScalarUDF::new_from_impl(PlaceholderUDF::new(name))))
    }

    fn get_expr_planners(&self) -> &[Arc<dyn ExprPlanner>] { &self.expr_planners }

    fn get_type_planner(&self) -> Option<Arc<dyn TypePlanner>> {
        if let Some(type_planner) = &self.type_planner {
            Some(Arc::clone(type_planner))
        } else {
            None
        }
    }

    fn get_table_source(&self, name: TableReference) -> Result<Arc<dyn TableSource>> {
        let name = self.resolve_table_ref(name);
        self.tables
            .get(&name)
            .cloned()
            .ok_or_else(|| plan_datafusion_err!("table '{name}' not found"))
    }

    fn get_table_function_source(
        &self,
        name: &str,
        args: Vec<Expr>,
    ) -> Result<Arc<dyn TableSource>> {
        let tbl_func = self
            .state
            .table_functions()
            .get(name)
            .cloned()
            .ok_or_else(|| plan_datafusion_err!("table function '{name}' not found"))?;
        let provider = tbl_func.create_table_provider(&args)?;

        Ok(provider_as_source(provider))
    }

    /// Create a new CTE work table for a recursive CTE logical plan
    /// This table will be used in conjunction with a Worktable physical plan
    /// to read and write each iteration of a recursive CTE
    fn create_cte_work_table(&self, name: &str, schema: SchemaRef) -> Result<Arc<dyn TableSource>> {
        let table = Arc::new(CteWorkTable::new(name, schema));
        Ok(provider_as_source(table))
    }

    fn get_aggregate_meta(&self, name: &str) -> Option<Arc<AggregateUDF>> {
        self.state.aggregate_functions().get(name).cloned()
    }

    fn get_window_meta(&self, name: &str) -> Option<Arc<WindowUDF>> {
        self.state.window_functions().get(name).cloned()
    }

    fn get_variable_type(&self, variable_names: &[String]) -> Option<DataType> {
        if variable_names.is_empty() {
            return None;
        }

        let provider_type = if is_system_variables(variable_names) {
            VarType::System
        } else {
            VarType::UserDefined
        };

        self.state
            .execution_props()
            .var_providers
            .as_ref()
            .and_then(|provider| provider.get(&provider_type)?.get_type(variable_names))
    }

    fn options(&self) -> &ConfigOptions { self.state.config_options() }

    /// Return the names of registered scalar UDFs.
    fn udf_names(&self) -> Vec<String> { self.state.scalar_functions().keys().cloned().collect() }

    fn udaf_names(&self) -> Vec<String> {
        self.state.aggregate_functions().keys().cloned().collect()
    }

    fn udwf_names(&self) -> Vec<String> { self.state.window_functions().keys().cloned().collect() }

    fn get_file_type(&self, ext: &str) -> Result<Arc<dyn FileType>> {
        self.state
            .get_file_format_factory(ext)
            .ok_or(plan_datafusion_err!("There is no registered file format with ext {ext}"))
            .map(|file_type| format_as_file_type(file_type))
    }
}

#[cfg(all(test, feature = "test-utils"))]
mod tests {
    use std::collections::HashMap;
    use std::sync::Arc;

    use datafusion::arrow::datatypes::{DataType, Field, Schema};
    use datafusion::common::DFSchema;
    use datafusion::logical_expr::planner::{
        ExprPlanner, PlannerResult, RawBinaryExpr, TypePlanner,
    };
    use datafusion::prelude::{SessionContext, lit};
    use datafusion::sql::TableReference;
    use datafusion::sql::sqlparser::ast;

    use super::*;

    // Mock TypePlanner for testing
    #[derive(Debug)]
    struct MockTypePlanner;

    impl TypePlanner for MockTypePlanner {
        fn plan_type(&self, _expr: &ast::DataType) -> Result<Option<DataType>> {
            Ok(Some(DataType::Utf8))
        }
    }

    // Mock ExprPlanner for testing
    #[derive(Debug)]
    struct MockExprPlanner;

    impl ExprPlanner for MockExprPlanner {
        fn plan_binary_op(
            &self,
            expr: RawBinaryExpr,
            _schema: &DFSchema,
        ) -> Result<PlannerResult<RawBinaryExpr>> {
            Ok(PlannerResult::Original(expr))
        }
    }

    fn create_test_context_provider() -> ClickHouseContextProvider {
        let ctx = SessionContext::new();
        let state = ctx.state();
        let tables = HashMap::new();
        ClickHouseContextProvider::new(state, tables)
    }

    #[test]
    fn test_with_expr_planner() {
        let mut provider = create_test_context_provider();
        assert!(provider.expr_planners.is_empty());

        let expr_planner = Arc::new(MockExprPlanner) as Arc<dyn ExprPlanner>;
        provider = provider.with_expr_planner(Arc::clone(&expr_planner));

        assert_eq!(provider.expr_planners.len(), 1);
        assert_eq!(provider.get_expr_planners().len(), 1);
    }

    #[test]
    fn test_with_type_planner() {
        let mut provider = create_test_context_provider();
        assert!(provider.type_planner.is_none());

        let type_planner = Arc::new(MockTypePlanner) as Arc<dyn TypePlanner>;
        provider = provider.with_type_planner(Arc::clone(&type_planner));

        assert!(provider.type_planner.is_some());
    }

    #[test]
    fn test_get_type_planner() {
        let provider = create_test_context_provider();
        assert!(provider.get_type_planner().is_none());

        let type_planner = Arc::new(MockTypePlanner) as Arc<dyn TypePlanner>;
        let provider = provider.with_type_planner(Arc::clone(&type_planner));

        assert!(provider.get_type_planner().is_some());
    }

    #[test]
    fn test_get_table_function_source_not_found() {
        let provider = create_test_context_provider();
        let args = vec![lit("test")];

        let result = provider.get_table_function_source("nonexistent_function", args);
        assert!(result.is_err());
    }

    #[test]
    fn test_create_cte_work_table() {
        let provider = create_test_context_provider();
        let schema = Arc::new(Schema::new(vec![
            Field::new("id", DataType::Int32, false),
            Field::new("name", DataType::Utf8, true),
        ]));

        let result = provider.create_cte_work_table("test_cte", Arc::clone(&schema));
        assert!(result.is_ok());

        let table_source = result.unwrap();
        assert_eq!(table_source.schema(), schema);
    }

    #[test]
    fn test_get_variable_type_empty() {
        let provider = create_test_context_provider();
        let result = provider.get_variable_type(&[]);
        assert!(result.is_none());
    }

    #[test]
    fn test_get_variable_type_system_variables() {
        let provider = create_test_context_provider();
        // System variables start with @@
        let result = provider.get_variable_type(&["@@version".to_string()]);
        // Since no variable providers are set up, this should return None
        assert!(result.is_none());
    }

    #[test]
    fn test_get_variable_type_user_defined() {
        let provider = create_test_context_provider();
        // User-defined variables don't start with @@
        let result = provider.get_variable_type(&["user_var".to_string()]);
        // Since no variable providers are set up, this should return None
        assert!(result.is_none());
    }

    #[test]
    fn test_get_file_type_unknown_extension() {
        let provider = create_test_context_provider();
        let result = provider.get_file_type("unknown_ext");
        assert!(result.is_err());
    }

    #[test]
    fn test_get_file_type_known_extension() {
        let provider = create_test_context_provider();
        // CSV should be a known file type in DataFusion
        let result = provider.get_file_type("csv");
        assert!(result.is_ok());
    }

    #[test]
    fn test_get_function_meta_clickhouse_udf() {
        let provider = create_test_context_provider();

        // Test clickhouse UDF alias
        let result = provider.get_function_meta("clickhouse");
        assert!(result.is_some());
        let udf = result.unwrap();
        assert_eq!(udf.name(), "clickhouse");
    }

    #[test]
    fn test_get_function_meta_placeholder_udf() {
        let provider = create_test_context_provider();

        // Test unknown function should return placeholder UDF
        let result = provider.get_function_meta("unknown_function");
        assert!(result.is_some());
        let udf = result.unwrap();
        assert_eq!(udf.name(), "unknown_function");
    }

    #[test]
    fn test_get_function_meta_aggregate_function() {
        let provider = create_test_context_provider();

        // Test known aggregate function should return None (not wrapped as ScalarUDF)
        let result = provider.get_function_meta("sum");
        assert!(result.is_none());
    }

    #[test]
    fn test_get_function_meta_window_function() {
        let provider = create_test_context_provider();

        // Test known window function should return None (not wrapped as ScalarUDF)
        let result = provider.get_function_meta("row_number");
        assert!(result.is_none());
    }

    #[test]
    fn test_get_table_source_not_found() {
        let provider = create_test_context_provider();
        let table_ref = TableReference::bare("nonexistent_table");

        let result = provider.get_table_source(table_ref);
        assert!(result.is_err());
    }

    #[test]
    fn test_resolve_table_ref() {
        let provider = create_test_context_provider();

        // Test bare table reference
        let table_ref = TableReference::bare("test_table");
        let resolved = provider.resolve_table_ref(table_ref);
        assert_eq!(resolved.table.as_ref(), "test_table");

        // Test partial table reference (schema.table)
        let table_ref = TableReference::partial("test_schema", "test_table");
        let resolved = provider.resolve_table_ref(table_ref);
        assert_eq!(resolved.schema.as_ref(), "test_schema");
        assert_eq!(resolved.table.as_ref(), "test_table");

        // Test full table reference (catalog.schema.table)
        let table_ref = TableReference::full("test_catalog", "test_schema", "test_table");
        let resolved = provider.resolve_table_ref(table_ref);
        assert_eq!(resolved.catalog.as_ref(), "test_catalog");
        assert_eq!(resolved.schema.as_ref(), "test_schema");
        assert_eq!(resolved.table.as_ref(), "test_table");
    }

    #[test]
    fn test_udf_names() {
        let provider = create_test_context_provider();
        let udf_names = provider.udf_names();
        // Should return the names of registered scalar functions
        // The exact contents depend on DataFusion's built-in functions
        assert!(!udf_names.is_empty());
    }

    #[test]
    fn test_udaf_names() {
        let provider = create_test_context_provider();
        let udaf_names = provider.udaf_names();
        // Should return the names of registered aggregate functions
        assert!(!udaf_names.is_empty());
        assert!(udaf_names.contains(&"sum".to_string()));
        assert!(udaf_names.contains(&"count".to_string()));
    }

    #[test]
    fn test_udwf_names() {
        let provider = create_test_context_provider();
        let udwf_names = provider.udwf_names();
        // Should return the names of registered window functions
        assert!(!udwf_names.is_empty());
        assert!(udwf_names.contains(&"row_number".to_string()));
    }

    #[test]
    fn test_options() {
        let provider = create_test_context_provider();
        let options = provider.options();
        // Should return ConfigOptions from the session state
        assert!(!options.catalog.default_catalog.is_empty());
        assert!(!options.catalog.default_schema.is_empty());
    }

    #[test]
    fn test_get_aggregate_meta() {
        let provider = create_test_context_provider();

        // Test known aggregate function
        let result = provider.get_aggregate_meta("sum");
        assert!(result.is_some());
        let udf = result.unwrap();
        assert_eq!(udf.name().to_lowercase().as_str(), "sum");

        // Test unknown aggregate function
        let result = provider.get_aggregate_meta("unknown_aggregate");
        assert!(result.is_none());
    }

    #[test]
    fn test_get_window_meta() {
        let provider = create_test_context_provider();

        // Test known window function
        let result = provider.get_window_meta("row_number");
        assert!(result.is_some());
        let udf = result.unwrap();
        assert_eq!(udf.name().to_lowercase().as_str(), "row_number");

        // Test unknown window function
        let result = provider.get_window_meta("unknown_window");
        assert!(result.is_none());
    }
}