icydb_core/db/session/

mod.rs

//! Module: session
//! Responsibility: user-facing query/write execution facade over db executors.
//! Does not own: planning semantics, cursor validation rules, or storage mutation protocol.
//! Boundary: converts fluent/query intent calls into executor operations and response DTOs.

mod query;
mod response;
#[cfg(feature = "sql")]
mod sql;
///
/// TESTS
///
#[cfg(all(test, feature = "sql"))]
mod tests;
mod write;

use crate::{
    db::{
        Db, EntityFieldDescription, EntityRuntimeHooks, EntitySchemaDescription, FluentDeleteQuery,
        FluentLoadQuery, IndexState, IntegrityReport, MissingRowPolicy, PersistedRow, Query,
        QueryError, StorageReport, StoreRegistry, WriteBatchResponse,
        commit::CommitSchemaFingerprint,
        executor::{DeleteExecutor, EntityAuthority, LoadExecutor, SaveExecutor},
        query::plan::{GeneratedExpressionCandidateIndex, VisibleIndexes},
        schema::{
            AcceptedRowDecodeContract, AcceptedRowLayoutRuntimeDescriptor, AcceptedSchemaSnapshot,
            SchemaInfo, accepted_commit_schema_fingerprint_for_model, describe_entity_fields,
            describe_entity_fields_with_persisted_schema, describe_entity_model,
            describe_entity_model_with_persisted_schema, ensure_accepted_schema_snapshot,
            show_indexes_for_model, show_indexes_for_model_with_runtime_state,
        },
    },
    error::InternalError,
    metrics::sink::{ExecKind, MetricsSink, record_exec_error_for_path, with_metrics_sink},
    model::entity::EntityModel,
    traits::{CanisterKind, EntityKind, EntityValue, Path},
    value::Value,
};
use std::thread::LocalKey;

#[cfg(feature = "diagnostics")]
pub use query::{
    DirectDataRowAttribution, GroupedCountAttribution, GroupedExecutionAttribution,
    QueryExecutionAttribution,
};
pub(in crate::db) use response::finalize_structural_grouped_projection_result;
pub(in crate::db) use response::{finalize_scalar_paged_execution, sql_grouped_cursor_from_bytes};
#[cfg(feature = "sql")]
pub use sql::SqlStatementResult;
#[cfg(all(feature = "sql", feature = "diagnostics"))]
pub use sql::{
    SqlCompileAttribution, SqlExecutionAttribution, SqlPureCoveringAttribution,
    SqlQueryCacheAttribution, SqlQueryExecutionAttribution, SqlScalarAggregateAttribution,
};
#[cfg(all(feature = "sql", feature = "diagnostics"))]
pub use sql::{SqlProjectionMaterializationMetrics, with_sql_projection_materialization_metrics};

///
/// DbSession
///
/// Session-scoped database handle with policy (debug, metrics) and execution routing.
///

pub struct DbSession<C: CanisterKind> {
    db: Db<C>,
    debug: bool,
    metrics: Option<&'static dyn MetricsSink>,
}

impl<C: CanisterKind> DbSession<C> {
    /// Construct one session facade for a database handle.
    #[must_use]
    pub(crate) const fn new(db: Db<C>) -> Self {
        Self {
            db,
            debug: false,
            metrics: None,
        }
    }

    /// Construct one session facade from store registry and runtime hooks.
    #[must_use]
    pub const fn new_with_hooks(
        store: &'static LocalKey<StoreRegistry>,
        entity_runtime_hooks: &'static [EntityRuntimeHooks<C>],
    ) -> Self {
        Self::new(Db::new_with_hooks(store, entity_runtime_hooks))
    }

    /// Enable debug execution behavior where supported by executors.
    #[must_use]
    pub const fn debug(mut self) -> Self {
        self.debug = true;
        self
    }

    /// Attach one metrics sink for all session-executed operations.
    #[must_use]
    pub const fn metrics_sink(mut self, sink: &'static dyn MetricsSink) -> Self {
        self.metrics = Some(sink);
        self
    }

    // Shared fluent load wrapper construction keeps the session boundary in
    // one place when load entry points differ only by missing-row policy.
    const fn fluent_load_query<E>(&self, consistency: MissingRowPolicy) -> FluentLoadQuery<'_, E>
    where
        E: EntityKind<Canister = C>,
    {
        FluentLoadQuery::new(self, Query::new(consistency))
    }

    // Shared fluent delete wrapper construction keeps the delete-mode handoff
    // explicit at the session boundary instead of reassembling the same query
    // shell in each public entry point.
    fn fluent_delete_query<E>(&self, consistency: MissingRowPolicy) -> FluentDeleteQuery<'_, E>
    where
        E: PersistedRow<Canister = C>,
    {
        FluentDeleteQuery::new(self, Query::new(consistency).delete())
    }

    fn with_metrics<T>(&self, f: impl FnOnce() -> T) -> T {
        if let Some(sink) = self.metrics {
            with_metrics_sink(sink, f)
        } else {
            f()
        }
    }

    // Shared save-facade wrapper keeps metrics wiring and response shaping uniform.
    fn execute_save_with<E, T, R>(
        &self,
        op: impl FnOnce(SaveExecutor<E>) -> Result<T, InternalError>,
        map: impl FnOnce(T) -> R,
    ) -> Result<R, InternalError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        let (contract, schema_info, schema_fingerprint) = match self
            .with_metrics(|| self.ensure_generated_compatible_accepted_save_schema::<E>())
        {
            Ok(authority) => authority,
            Err(error) => {
                self.with_metrics(|| record_exec_error_for_path(ExecKind::Save, E::PATH, &error));

                return Err(error);
            }
        };
        let value = self.with_metrics(|| {
            op(self.save_executor::<E>(contract, schema_info, schema_fingerprint))
        })?;

        Ok(map(value))
    }

    // Execute save work after the caller has already proven that the accepted
    // row contract is generated-compatible. SQL and structural writes use this
    // after their pre-staging schema guard so mutation staging and save
    // execution do not rerun schema-store reconciliation in the same statement.
    fn execute_save_with_checked_accepted_row_contract<E, T, R>(
        &self,
        accepted_row_decode_contract: AcceptedRowDecodeContract,
        accepted_schema_info: SchemaInfo,
        accepted_schema_fingerprint: CommitSchemaFingerprint,
        op: impl FnOnce(SaveExecutor<E>) -> Result<T, InternalError>,
        map: impl FnOnce(T) -> R,
    ) -> Result<R, InternalError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        let value = self.with_metrics(|| {
            op(self.save_executor::<E>(
                accepted_row_decode_contract,
                accepted_schema_info,
                accepted_schema_fingerprint,
            ))
        })?;

        Ok(map(value))
    }

    // Shared save-facade wrappers keep response shape explicit at call sites.
    fn execute_save_entity<E>(
        &self,
        op: impl FnOnce(SaveExecutor<E>) -> Result<E, InternalError>,
    ) -> Result<E, InternalError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_save_with(op, std::convert::identity)
    }

    fn execute_save_batch<E>(
        &self,
        op: impl FnOnce(SaveExecutor<E>) -> Result<Vec<E>, InternalError>,
    ) -> Result<WriteBatchResponse<E>, InternalError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_save_with(op, WriteBatchResponse::new)
    }

    // ---------------------------------------------------------------------
    // Query entry points (public, fluent)
    // ---------------------------------------------------------------------

    /// Start a fluent load query with default missing-row policy (`Ignore`).
    #[must_use]
    pub const fn load<E>(&self) -> FluentLoadQuery<'_, E>
    where
        E: EntityKind<Canister = C>,
    {
        self.fluent_load_query(MissingRowPolicy::Ignore)
    }

    /// Start a fluent load query with explicit missing-row policy.
    #[must_use]
    pub const fn load_with_consistency<E>(
        &self,
        consistency: MissingRowPolicy,
    ) -> FluentLoadQuery<'_, E>
    where
        E: EntityKind<Canister = C>,
    {
        self.fluent_load_query(consistency)
    }

    /// Start a fluent delete query with default missing-row policy (`Ignore`).
    #[must_use]
    pub fn delete<E>(&self) -> FluentDeleteQuery<'_, E>
    where
        E: PersistedRow<Canister = C>,
    {
        self.fluent_delete_query(MissingRowPolicy::Ignore)
    }

    /// Start a fluent delete query with explicit missing-row policy.
    #[must_use]
    pub fn delete_with_consistency<E>(
        &self,
        consistency: MissingRowPolicy,
    ) -> FluentDeleteQuery<'_, E>
    where
        E: PersistedRow<Canister = C>,
    {
        self.fluent_delete_query(consistency)
    }

    /// Return one constant scalar row equivalent to SQL `SELECT 1`.
    ///
    /// This terminal bypasses query planning and access routing entirely.
    #[must_use]
    pub const fn select_one(&self) -> Value {
        Value::Int(1)
    }

    /// Return one stable, human-readable index listing for the entity schema.
    ///
    /// Output format mirrors SQL-style introspection:
    /// - `PRIMARY KEY (field)`
    /// - `INDEX name (field_a, field_b)`
    /// - `UNIQUE INDEX name (field_a, field_b)`
    #[must_use]
    pub fn show_indexes<E>(&self) -> Vec<String>
    where
        E: EntityKind<Canister = C>,
    {
        self.show_indexes_for_store_model(E::Store::PATH, E::MODEL)
    }

    /// Return one stable, human-readable index listing for one schema model.
    ///
    /// This model-only helper is schema-owned and intentionally does not
    /// attach runtime lifecycle state because it does not carry store
    /// placement context.
    #[must_use]
    pub fn show_indexes_for_model(&self, model: &'static EntityModel) -> Vec<String> {
        show_indexes_for_model(model)
    }

    // Return one stable, human-readable index listing for one resolved
    // store/model pair, attaching the current runtime lifecycle state when the
    // registry can resolve the backing store handle.
    pub(in crate::db) fn show_indexes_for_store_model(
        &self,
        store_path: &str,
        model: &'static EntityModel,
    ) -> Vec<String> {
        let runtime_state = self
            .db
            .with_store_registry(|registry| registry.try_get_store(store_path).ok())
            .map(|store| store.index_state());

        show_indexes_for_model_with_runtime_state(model, runtime_state)
    }

    /// Return one stable generated-model list of field descriptors.
    ///
    /// This infallible Rust metadata helper intentionally reports the compiled
    /// schema model. Use `try_show_columns` for the accepted persisted-schema
    /// view used by SQL and diagnostics surfaces.
    #[must_use]
    pub fn show_columns<E>(&self) -> Vec<EntityFieldDescription>
    where
        E: EntityKind<Canister = C>,
    {
        self.show_columns_for_model(E::MODEL)
    }

    /// Return one stable generated-model list of field descriptors.
    #[must_use]
    pub fn show_columns_for_model(
        &self,
        model: &'static EntityModel,
    ) -> Vec<EntityFieldDescription> {
        describe_entity_fields(model)
    }

    /// Return field descriptors using the accepted persisted schema snapshot.
    ///
    /// This fallible variant is intended for SQL and diagnostics surfaces that
    /// can report schema reconciliation failures. The infallible
    /// `show_columns` helper remains generated-model based.
    pub fn try_show_columns<E>(&self) -> Result<Vec<EntityFieldDescription>, InternalError>
    where
        E: EntityKind<Canister = C>,
    {
        let snapshot = self.ensure_accepted_schema_snapshot::<E>()?;

        Ok(describe_entity_fields_with_persisted_schema(&snapshot))
    }

    /// Return one stable list of runtime-registered entity names.
    #[must_use]
    pub fn show_entities(&self) -> Vec<String> {
        self.db.runtime_entity_names()
    }

    /// Return one stable list of runtime-registered entity names.
    ///
    /// `SHOW TABLES` is only an alias for `SHOW ENTITIES`, so the typed
    /// metadata surface keeps the same alias relationship.
    #[must_use]
    pub fn show_tables(&self) -> Vec<String> {
        self.show_entities()
    }

    // Resolve the exact secondary-index set that is visible to planner-owned
    // query planning for one recovered store/model pair.
    fn visible_indexes_for_store_accepted_schema(
        &self,
        store_path: &str,
        model: &'static EntityModel,
        schema_info: &SchemaInfo,
    ) -> Result<VisibleIndexes<'static>, QueryError> {
        // Phase 1: resolve the recovered store state once at the session
        // boundary so query/executor planning does not reopen lifecycle checks.
        let store = self
            .db
            .recovered_store(store_path)
            .map_err(QueryError::execute)?;
        let state = store.index_state();
        if state != IndexState::Ready {
            return Ok(VisibleIndexes::none());
        }
        debug_assert_eq!(state, IndexState::Ready);

        // Phase 2: planner-visible field-path indexes are accepted schema
        // contracts once the recovered store is query-visible. The remaining
        // generated candidates are expression-index only.
        let visible_indexes = VisibleIndexes::accepted_schema_visible(model.indexes(), schema_info);
        debug_assert!(
            visible_indexes
                .generated_expression_candidate_indexes()
                .iter()
                .all(GeneratedExpressionCandidateIndex::has_expression_key_items),
        );
        debug_assert!(visible_indexes.accepted_field_path_contracts_are_consistent());

        Ok(visible_indexes)
    }

    /// Return one generated-model schema description for the entity.
    ///
    /// This is a typed `DESCRIBE`-style introspection surface consumed by
    /// developer tooling and pre-EXPLAIN debugging when a non-failing compiled
    /// schema view is required.
    #[must_use]
    pub fn describe_entity<E>(&self) -> EntitySchemaDescription
    where
        E: EntityKind<Canister = C>,
    {
        self.describe_entity_model(E::MODEL)
    }

    /// Return one generated-model schema description for one schema model.
    #[must_use]
    pub fn describe_entity_model(&self, model: &'static EntityModel) -> EntitySchemaDescription {
        describe_entity_model(model)
    }

    /// Return a schema description using the accepted persisted schema snapshot.
    ///
    /// This is the live-schema counterpart to `describe_entity`. It is fallible
    /// because loading accepted schema authority can fail if startup
    /// reconciliation rejects the stored metadata.
    pub fn try_describe_entity<E>(&self) -> Result<EntitySchemaDescription, InternalError>
    where
        E: EntityKind<Canister = C>,
    {
        let snapshot = self.ensure_accepted_schema_snapshot::<E>()?;

        Ok(describe_entity_model_with_persisted_schema(
            E::MODEL,
            &snapshot,
        ))
    }

    // Ensure and return the accepted schema snapshot for one generated entity.
    // This may write the first snapshot for an empty store; otherwise it loads
    // the latest stored snapshot and applies the current exact-match policy.
    fn ensure_accepted_schema_snapshot<E>(&self) -> Result<AcceptedSchemaSnapshot, InternalError>
    where
        E: EntityKind<Canister = C>,
    {
        let store = self.db.recovered_store(E::Store::PATH)?;

        store.with_schema_mut(|schema_store| {
            ensure_accepted_schema_snapshot(schema_store, E::ENTITY_TAG, E::PATH, E::MODEL)
        })
    }

    // Build the accepted schema-info projection for one typed entity. Fluent
    // terminal adapters use this before constructing slot-bound descriptors so
    // field slot authority comes from the accepted schema snapshot.
    pub(in crate::db) fn accepted_schema_info_for_entity<E>(
        &self,
    ) -> Result<SchemaInfo, InternalError>
    where
        E: EntityKind<Canister = C>,
    {
        let accepted_schema = self.ensure_accepted_schema_snapshot::<E>()?;

        Ok(SchemaInfo::from_accepted_snapshot_for_model(
            E::MODEL,
            &accepted_schema,
        ))
    }

    // Derive typed executor authority from an accepted snapshot the caller
    // already loaded, avoiding a second schema-store pass in SQL write/select
    // adapters that need both write descriptors and read selector authority.
    pub(in crate::db) fn accepted_entity_authority_for_schema<E>(
        accepted_schema: &AcceptedSchemaSnapshot,
    ) -> Result<EntityAuthority, InternalError>
    where
        E: EntityKind<Canister = C>,
    {
        EntityAuthority::from_accepted_schema_for_type::<E>(accepted_schema)
    }

    // Load the accepted schema snapshot and derive the matching typed executor
    // authority as one pair so typed session entrypoints cannot accidentally
    // mix accepted schema fingerprints with generated row-layout authority.
    pub(in crate::db) fn accepted_entity_authority<E>(
        &self,
    ) -> Result<(AcceptedSchemaSnapshot, EntityAuthority), InternalError>
    where
        E: EntityKind<Canister = C>,
    {
        let accepted_schema = self.ensure_accepted_schema_snapshot::<E>()?;
        let authority = Self::accepted_entity_authority_for_schema::<E>(&accepted_schema)?;

        Ok((accepted_schema, authority))
    }

    // Ensure accepted schema metadata is safe for write paths that still encode
    // rows through generated field contracts. Returning only the snapshot keeps
    // SQL write type checks unchanged while the schema-runtime descriptor guard
    // rejects unsupported layout or payload drift before mutation staging.
    fn ensure_generated_compatible_accepted_save_schema<E>(
        &self,
    ) -> Result<
        (
            AcceptedRowDecodeContract,
            SchemaInfo,
            CommitSchemaFingerprint,
        ),
        InternalError,
    >
    where
        E: EntityKind<Canister = C>,
    {
        let accepted_schema = self.ensure_accepted_schema_snapshot::<E>()?;
        let (accepted_row_layout, _) =
            AcceptedRowLayoutRuntimeDescriptor::from_generated_compatible_schema(
                &accepted_schema,
                E::MODEL,
            )?;
        let schema_info = SchemaInfo::from_accepted_snapshot_for_model(E::MODEL, &accepted_schema);
        let schema_fingerprint =
            accepted_commit_schema_fingerprint_for_model(E::MODEL, &accepted_schema)?;

        Ok((
            accepted_row_layout.row_decode_contract(),
            schema_info,
            schema_fingerprint,
        ))
    }

    /// Build one point-in-time storage report for observability endpoints.
    pub fn storage_report(
        &self,
        name_to_path: &[(&'static str, &'static str)],
    ) -> Result<StorageReport, InternalError> {
        self.db.storage_report(name_to_path)
    }

    /// Build one point-in-time storage report using default entity-path labels.
    pub fn storage_report_default(&self) -> Result<StorageReport, InternalError> {
        self.db.storage_report_default()
    }

    /// Build one point-in-time integrity scan report for observability endpoints.
    pub fn integrity_report(&self) -> Result<IntegrityReport, InternalError> {
        self.db.integrity_report()
    }

    // ---------------------------------------------------------------------
    // Low-level executors (crate-internal; execution primitives)
    // ---------------------------------------------------------------------

    #[must_use]
    pub(in crate::db) const fn load_executor<E>(&self) -> LoadExecutor<E>
    where
        E: EntityKind<Canister = C> + EntityValue,
    {
        LoadExecutor::new(self.db, self.debug)
    }

    #[must_use]
    pub(in crate::db) const fn delete_executor<E>(&self) -> DeleteExecutor<E>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        DeleteExecutor::new(self.db)
    }

    #[must_use]
    pub(in crate::db) const fn save_executor<E>(
        &self,
        accepted_row_decode_contract: AcceptedRowDecodeContract,
        accepted_schema_info: SchemaInfo,
        accepted_schema_fingerprint: CommitSchemaFingerprint,
    ) -> SaveExecutor<E>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        SaveExecutor::new_with_accepted_contract(
            self.db,
            self.debug,
            accepted_row_decode_contract,
            accepted_schema_info,
            accepted_schema_fingerprint,
        )
    }
}