icydb_core/db/session/

query.rs

//! Module: db::session::query
//! Responsibility: session-bound query planning, explain, and cursor execution
//! helpers that recover store visibility before delegating to query-owned logic.
//! Does not own: query intent construction or executor runtime semantics.
//! Boundary: resolves session visibility and cursor policy before handing work to the planner/executor.

mod cache;

#[cfg(feature = "diagnostics")]
use crate::db::executor::{
    GroupedCountAttribution, GroupedExecutePhaseAttribution, ScalarExecutePhaseAttribution,
};
use crate::{
    db::{
        DbSession, EntityResponse, LoadQueryResult, PagedGroupedExecutionWithTrace,
        PagedLoadExecutionWithTrace, PersistedRow, Query, QueryError, QueryTracePlan,
        TraceExecutionFamily,
        access::summarize_executable_access_plan,
        cursor::{
            CursorPlanError, decode_optional_cursor_token, decode_optional_grouped_cursor_token,
        },
        diagnostics::ExecutionTrace,
        executor::{
            ExecutionFamily, ExecutorPlanError, GroupedCursorPage, LoadExecutor,
            PreparedExecutionPlan, ScalarNumericFieldBoundaryRequest,
            ScalarProjectionBoundaryOutput, ScalarProjectionBoundaryRequest,
            ScalarTerminalBoundaryOutput, ScalarTerminalBoundaryRequest,
        },
        query::builder::{
            PreparedFluentAggregateExplainStrategy,
            PreparedFluentExistingRowsTerminalRuntimeRequest,
            PreparedFluentExistingRowsTerminalStrategy, PreparedFluentNumericFieldRuntimeRequest,
            PreparedFluentNumericFieldStrategy, PreparedFluentOrderSensitiveTerminalRuntimeRequest,
            PreparedFluentOrderSensitiveTerminalStrategy, PreparedFluentProjectionRuntimeRequest,
            PreparedFluentProjectionStrategy, PreparedFluentScalarTerminalRuntimeRequest,
            PreparedFluentScalarTerminalStrategy,
        },
        query::explain::{
            ExplainAggregateTerminalPlan, ExplainExecutionNodeDescriptor, ExplainPlan,
        },
        query::fluent::load::{FluentProjectionTerminalOutput, FluentScalarTerminalOutput},
        query::{
            intent::{CompiledQuery, PlannedQuery},
            plan::{FieldSlot, QueryMode},
        },
        session::{finalize_grouped_paged_execution, finalize_scalar_paged_execution},
    },
    error::InternalError,
    traits::{CanisterKind, EntityKind, EntityValue, Path},
    types::{Decimal, Id},
    value::Value,
};
pub(in crate::db) use cache::QueryPlanCacheAttribution;
#[cfg(test)]
pub(in crate::db) use cache::QueryPlanVisibility;
pub(in crate::db::session) use cache::query_plan_cache_reuse_event;
#[cfg(feature = "diagnostics")]
use candid::CandidType;
#[cfg(feature = "diagnostics")]
use serde::Deserialize;

// Translate executor route-family selection into the query-owned trace label
// at the session boundary so trace DTOs do not depend on executor types.
const fn trace_execution_family_from_executor(family: ExecutionFamily) -> TraceExecutionFamily {
    match family {
        ExecutionFamily::PrimaryKey => TraceExecutionFamily::PrimaryKey,
        ExecutionFamily::Ordered => TraceExecutionFamily::Ordered,
        ExecutionFamily::Grouped => TraceExecutionFamily::Grouped,
    }
}

// Convert executor plan-surface failures at the session boundary so query error
// types do not import executor-owned error enums.
pub(in crate::db::session) fn query_error_from_executor_plan_error(
    err: ExecutorPlanError,
) -> QueryError {
    match err {
        ExecutorPlanError::Cursor(err) => QueryError::from_cursor_plan_error(*err),
    }
}

///
/// QueryExecutionAttribution
///
/// QueryExecutionAttribution records the top-level compile/execute split for
/// typed/fluent query execution at the session boundary.
///
#[cfg(feature = "diagnostics")]
#[derive(CandidType, Clone, Debug, Deserialize, Eq, PartialEq)]
pub struct QueryExecutionAttribution {
    pub compile_local_instructions: u64,
    pub plan_lookup_local_instructions: u64,
    pub executor_invocation_local_instructions: u64,
    pub response_finalization_local_instructions: u64,
    pub runtime_local_instructions: u64,
    pub finalize_local_instructions: u64,
    pub direct_data_row_scan_local_instructions: u64,
    pub direct_data_row_key_stream_local_instructions: u64,
    pub direct_data_row_row_read_local_instructions: u64,
    pub direct_data_row_key_encode_local_instructions: u64,
    pub direct_data_row_store_get_local_instructions: u64,
    pub direct_data_row_order_window_local_instructions: u64,
    pub direct_data_row_page_window_local_instructions: u64,
    pub grouped_stream_local_instructions: u64,
    pub grouped_fold_local_instructions: u64,
    pub grouped_finalize_local_instructions: u64,
    pub grouped_count_borrowed_hash_computations: u64,
    pub grouped_count_bucket_candidate_checks: u64,
    pub grouped_count_existing_group_hits: u64,
    pub grouped_count_new_group_inserts: u64,
    pub grouped_count_row_materialization_local_instructions: u64,
    pub grouped_count_group_lookup_local_instructions: u64,
    pub grouped_count_existing_group_update_local_instructions: u64,
    pub grouped_count_new_group_insert_local_instructions: u64,
    pub response_decode_local_instructions: u64,
    pub execute_local_instructions: u64,
    pub total_local_instructions: u64,
    pub shared_query_plan_cache_hits: u64,
    pub shared_query_plan_cache_misses: u64,
}

#[cfg(feature = "diagnostics")]
#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
struct QueryExecutePhaseAttribution {
    executor_invocation_local_instructions: u64,
    response_finalization_local_instructions: u64,
    runtime_local_instructions: u64,
    finalize_local_instructions: u64,
    direct_data_row_scan_local_instructions: u64,
    direct_data_row_key_stream_local_instructions: u64,
    direct_data_row_row_read_local_instructions: u64,
    direct_data_row_key_encode_local_instructions: u64,
    direct_data_row_store_get_local_instructions: u64,
    direct_data_row_order_window_local_instructions: u64,
    direct_data_row_page_window_local_instructions: u64,
    grouped_stream_local_instructions: u64,
    grouped_fold_local_instructions: u64,
    grouped_finalize_local_instructions: u64,
    grouped_count: GroupedCountAttribution,
}

#[cfg(feature = "diagnostics")]
#[expect(
    clippy::missing_const_for_fn,
    reason = "the wasm32 branch reads the runtime performance counter and cannot be const"
)]
fn read_query_local_instruction_counter() -> u64 {
    #[cfg(target_arch = "wasm32")]
    {
        canic_cdk::api::performance_counter(1)
    }

    #[cfg(not(target_arch = "wasm32"))]
    {
        0
    }
}

#[cfg(feature = "diagnostics")]
fn measure_query_stage<T, E>(run: impl FnOnce() -> Result<T, E>) -> (u64, Result<T, E>) {
    let start = read_query_local_instruction_counter();
    let result = run();
    let delta = read_query_local_instruction_counter().saturating_sub(start);

    (delta, result)
}

impl<C: CanisterKind> DbSession<C> {
    #[cfg(feature = "diagnostics")]
    const fn empty_query_execute_phase_attribution() -> QueryExecutePhaseAttribution {
        QueryExecutePhaseAttribution {
            executor_invocation_local_instructions: 0,
            response_finalization_local_instructions: 0,
            runtime_local_instructions: 0,
            finalize_local_instructions: 0,
            direct_data_row_scan_local_instructions: 0,
            direct_data_row_key_stream_local_instructions: 0,
            direct_data_row_row_read_local_instructions: 0,
            direct_data_row_key_encode_local_instructions: 0,
            direct_data_row_store_get_local_instructions: 0,
            direct_data_row_order_window_local_instructions: 0,
            direct_data_row_page_window_local_instructions: 0,
            grouped_stream_local_instructions: 0,
            grouped_fold_local_instructions: 0,
            grouped_finalize_local_instructions: 0,
            grouped_count: GroupedCountAttribution::none(),
        }
    }

    #[cfg(feature = "diagnostics")]
    const fn scalar_query_execute_phase_attribution(
        phase: ScalarExecutePhaseAttribution,
        executor_invocation_local_instructions: u64,
    ) -> QueryExecutePhaseAttribution {
        QueryExecutePhaseAttribution {
            executor_invocation_local_instructions,
            response_finalization_local_instructions: 0,
            runtime_local_instructions: phase.runtime_local_instructions,
            finalize_local_instructions: phase.finalize_local_instructions,
            direct_data_row_scan_local_instructions: phase.direct_data_row_scan_local_instructions,
            direct_data_row_key_stream_local_instructions: phase
                .direct_data_row_key_stream_local_instructions,
            direct_data_row_row_read_local_instructions: phase
                .direct_data_row_row_read_local_instructions,
            direct_data_row_key_encode_local_instructions: phase
                .direct_data_row_key_encode_local_instructions,
            direct_data_row_store_get_local_instructions: phase
                .direct_data_row_store_get_local_instructions,
            direct_data_row_order_window_local_instructions: phase
                .direct_data_row_order_window_local_instructions,
            direct_data_row_page_window_local_instructions: phase
                .direct_data_row_page_window_local_instructions,
            grouped_stream_local_instructions: 0,
            grouped_fold_local_instructions: 0,
            grouped_finalize_local_instructions: 0,
            grouped_count: GroupedCountAttribution::none(),
        }
    }

    #[cfg(feature = "diagnostics")]
    const fn grouped_query_execute_phase_attribution(
        phase: GroupedExecutePhaseAttribution,
        executor_invocation_local_instructions: u64,
        response_finalization_local_instructions: u64,
    ) -> QueryExecutePhaseAttribution {
        QueryExecutePhaseAttribution {
            executor_invocation_local_instructions,
            response_finalization_local_instructions,
            runtime_local_instructions: phase
                .stream_local_instructions
                .saturating_add(phase.fold_local_instructions),
            finalize_local_instructions: phase.finalize_local_instructions,
            direct_data_row_scan_local_instructions: 0,
            direct_data_row_key_stream_local_instructions: 0,
            direct_data_row_row_read_local_instructions: 0,
            direct_data_row_key_encode_local_instructions: 0,
            direct_data_row_store_get_local_instructions: 0,
            direct_data_row_order_window_local_instructions: 0,
            direct_data_row_page_window_local_instructions: 0,
            grouped_stream_local_instructions: phase.stream_local_instructions,
            grouped_fold_local_instructions: phase.fold_local_instructions,
            grouped_finalize_local_instructions: phase.finalize_local_instructions,
            grouped_count: phase.grouped_count,
        }
    }

    // Compile one typed query using only the indexes currently visible for the
    // query's recovered store.
    pub(in crate::db) fn compile_query_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
    ) -> Result<CompiledQuery<E>, QueryError>
    where
        E: EntityKind<Canister = C>,
    {
        self.map_cached_shared_query_plan_for_entity(query, CompiledQuery::<E>::from_plan)
    }

    // Build one logical planned-query shell using only the indexes currently
    // visible for the query's recovered store.
    pub(in crate::db) fn planned_query_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
    ) -> Result<PlannedQuery<E>, QueryError>
    where
        E: EntityKind<Canister = C>,
    {
        self.map_cached_shared_query_plan_for_entity(query, PlannedQuery::<E>::from_plan)
    }

    // Project one logical explain payload using only planner-visible indexes.
    pub(in crate::db) fn explain_query_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
    ) -> Result<ExplainPlan, QueryError>
    where
        E: EntityKind<Canister = C>,
    {
        self.with_query_visible_indexes(query, Query::<E>::explain_with_visible_indexes)
    }

    // Hash one typed query plan using only the indexes currently visible for
    // the query's recovered store.
    pub(in crate::db) fn query_plan_hash_hex_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
    ) -> Result<String, QueryError>
    where
        E: EntityKind<Canister = C>,
    {
        self.with_query_visible_indexes(query, Query::<E>::plan_hash_hex_with_visible_indexes)
    }

    // Explain one load execution shape using only planner-visible
    // indexes from the recovered store state.
    pub(in crate::db) fn explain_query_execution_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
    ) -> Result<ExplainExecutionNodeDescriptor, QueryError>
    where
        E: EntityValue + EntityKind<Canister = C>,
    {
        self.with_query_visible_indexes(query, Query::<E>::explain_execution_with_visible_indexes)
    }

    // Render one load execution descriptor plus route diagnostics using
    // only planner-visible indexes from the recovered store state.
    pub(in crate::db) fn explain_query_execution_verbose_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
    ) -> Result<String, QueryError>
    where
        E: EntityValue + EntityKind<Canister = C>,
    {
        self.with_query_visible_indexes(query, |query, visible_indexes| {
            let (prepared_plan, cache_attribution) =
                self.cached_prepared_query_plan_for_entity(query)?;
            let mut plan = prepared_plan.logical_plan().clone();

            // Freeze the same planner-owned explain access-choice snapshot used
            // by the direct non-cached explain path before rendering verbose
            // diagnostics from the reused logical plan.
            plan.finalize_access_choice_for_model_with_indexes(
                query.structural().model(),
                visible_indexes.as_slice(),
            );

            query
                .structural()
                .finalized_execution_diagnostics_from_plan_with_descriptor_mutator(
                    &plan,
                    Some(query_plan_cache_reuse_event(cache_attribution)),
                    |_| {},
                )
                .map(|diagnostics| diagnostics.render_text_verbose())
        })
    }

    // Explain one prepared fluent aggregate terminal using only
    // planner-visible indexes from the recovered store state.
    pub(in crate::db) fn explain_query_prepared_aggregate_terminal_with_visible_indexes<E, S>(
        &self,
        query: &Query<E>,
        strategy: &S,
    ) -> Result<ExplainAggregateTerminalPlan, QueryError>
    where
        E: EntityValue + EntityKind<Canister = C>,
        S: PreparedFluentAggregateExplainStrategy,
    {
        self.with_query_visible_indexes(query, |query, visible_indexes| {
            query
                .explain_prepared_aggregate_terminal_with_visible_indexes(visible_indexes, strategy)
        })
    }

    // Explain one `bytes_by(field)` terminal using only planner-visible
    // indexes from the recovered store state.
    pub(in crate::db) fn explain_query_bytes_by_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
        target_field: &str,
    ) -> Result<ExplainExecutionNodeDescriptor, QueryError>
    where
        E: EntityValue + EntityKind<Canister = C>,
    {
        self.with_query_visible_indexes(query, |query, visible_indexes| {
            query.explain_bytes_by_with_visible_indexes(visible_indexes, target_field)
        })
    }

    // Explain one prepared fluent projection terminal using only
    // planner-visible indexes from the recovered store state.
    pub(in crate::db) fn explain_query_prepared_projection_terminal_with_visible_indexes<E>(
        &self,
        query: &Query<E>,
        strategy: &PreparedFluentProjectionStrategy,
    ) -> Result<ExplainExecutionNodeDescriptor, QueryError>
    where
        E: EntityValue + EntityKind<Canister = C>,
    {
        self.with_query_visible_indexes(query, |query, visible_indexes| {
            query.explain_prepared_projection_terminal_with_visible_indexes(
                visible_indexes,
                strategy,
            )
        })
    }

    // Validate that one execution strategy is admissible for scalar paged load
    // execution and fail closed on grouped/primary-key-only routes.
    fn ensure_scalar_paged_execution_family(family: ExecutionFamily) -> Result<(), QueryError> {
        match family {
            ExecutionFamily::PrimaryKey => Err(QueryError::invariant(
                CursorPlanError::cursor_requires_explicit_or_grouped_ordering_message(),
            )),
            ExecutionFamily::Ordered => Ok(()),
            ExecutionFamily::Grouped => Err(QueryError::invariant(
                "grouped queries execute via execute(), not page().execute()",
            )),
        }
    }

    // Validate that one execution strategy is admissible for the grouped
    // execution surface.
    fn ensure_grouped_execution_family(family: ExecutionFamily) -> Result<(), QueryError> {
        match family {
            ExecutionFamily::Grouped => Ok(()),
            ExecutionFamily::PrimaryKey | ExecutionFamily::Ordered => Err(QueryError::invariant(
                "grouped execution requires grouped logical plans",
            )),
        }
    }

    // Finalize one grouped cursor page into the outward grouped execution
    // payload so grouped cursor encoding and continuation-shape validation
    // stay owned by the session boundary.
    fn finalize_grouped_execution_page(
        page: GroupedCursorPage,
        trace: Option<ExecutionTrace>,
    ) -> Result<PagedGroupedExecutionWithTrace, QueryError> {
        finalize_grouped_paged_execution(page, trace)
    }

    /// Execute one scalar load/delete query and return materialized response rows.
    pub fn execute_query<E>(&self, query: &Query<E>) -> Result<EntityResponse<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        // Phase 1: compile typed intent into one prepared execution-plan contract.
        let mode = query.mode();
        let (plan, _) = self.cached_prepared_query_plan_for_entity::<E>(query)?;

        // Phase 2: delegate execution to the shared compiled-plan entry path.
        self.execute_query_dyn(mode, plan)
    }

    /// Execute one typed query while reporting the compile/execute split at
    /// the shared fluent query seam.
    #[cfg(feature = "diagnostics")]
    #[doc(hidden)]
    #[expect(
        clippy::too_many_lines,
        reason = "the diagnostics-only attribution path keeps grouped and scalar execution on one explicit compile/execute accounting seam"
    )]
    pub fn execute_query_result_with_attribution<E>(
        &self,
        query: &Query<E>,
    ) -> Result<(LoadQueryResult<E>, QueryExecutionAttribution), QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        // Phase 1: measure compile work at the typed/fluent boundary,
        // including the shared lower query-plan cache lookup/build exactly
        // once. This preserves honest hit/miss attribution without
        // double-building plans on one-shot cache misses.
        let (plan_lookup_local_instructions, plan_and_cache) =
            measure_query_stage(|| self.cached_prepared_query_plan_for_entity::<E>(query));
        let (plan, cache_attribution) = plan_and_cache?;
        let compile_local_instructions = plan_lookup_local_instructions;

        // Phase 2: execute one query result using the prepared plan produced
        // by the compile/cache boundary above.
        let result =
            || -> Result<(LoadQueryResult<E>, QueryExecutePhaseAttribution, u64), QueryError> {
                if query.has_grouping() {
                    let (executor_invocation_local_instructions, grouped_page) =
                        measure_query_stage(|| {
                            self.execute_grouped_plan_with(plan, None, |executor, plan, cursor| {
                                executor
                                    .execute_grouped_paged_with_cursor_traced_with_phase_attribution(
                                        plan, cursor,
                                    )
                            })
                        });
                    let (page, trace, phase_attribution) = grouped_page?;
                    let (response_finalization_local_instructions, grouped) =
                        measure_query_stage(|| Self::finalize_grouped_execution_page(page, trace));
                    let grouped = grouped?;

                    Ok((
                        LoadQueryResult::Grouped(grouped),
                        Self::grouped_query_execute_phase_attribution(
                            phase_attribution,
                            executor_invocation_local_instructions,
                            response_finalization_local_instructions,
                        ),
                        0,
                    ))
                } else {
                    match query.mode() {
                        QueryMode::Load(_) => {
                            let (executor_invocation_local_instructions, executed) =
                                measure_query_stage(|| {
                                    self.load_executor::<E>()
                                        .execute_with_phase_attribution(plan)
                                        .map_err(QueryError::execute)
                                });
                            let (rows, phase_attribution, response_decode_local_instructions) =
                                executed?;

                            Ok((
                                LoadQueryResult::Rows(rows),
                                Self::scalar_query_execute_phase_attribution(
                                    phase_attribution,
                                    executor_invocation_local_instructions,
                                ),
                                response_decode_local_instructions,
                            ))
                        }
                        QueryMode::Delete(_) => {
                            let (executor_invocation_local_instructions, result) =
                                measure_query_stage(|| self.execute_query_dyn(query.mode(), plan));
                            let result = result?;

                            Ok((
                                LoadQueryResult::Rows(result),
                                QueryExecutePhaseAttribution {
                                    executor_invocation_local_instructions,
                                    ..Self::empty_query_execute_phase_attribution()
                                },
                                0,
                            ))
                        }
                    }
                }
            }();
        let (result, execute_phase_attribution, response_decode_local_instructions) = result?;
        let execute_local_instructions = execute_phase_attribution
            .executor_invocation_local_instructions
            .saturating_add(execute_phase_attribution.response_finalization_local_instructions);
        let total_local_instructions =
            compile_local_instructions.saturating_add(execute_local_instructions);

        Ok((
            result,
            QueryExecutionAttribution {
                compile_local_instructions,
                plan_lookup_local_instructions,
                executor_invocation_local_instructions: execute_phase_attribution
                    .executor_invocation_local_instructions,
                response_finalization_local_instructions: execute_phase_attribution
                    .response_finalization_local_instructions,
                runtime_local_instructions: execute_phase_attribution.runtime_local_instructions,
                finalize_local_instructions: execute_phase_attribution.finalize_local_instructions,
                direct_data_row_scan_local_instructions: execute_phase_attribution
                    .direct_data_row_scan_local_instructions,
                direct_data_row_key_stream_local_instructions: execute_phase_attribution
                    .direct_data_row_key_stream_local_instructions,
                direct_data_row_row_read_local_instructions: execute_phase_attribution
                    .direct_data_row_row_read_local_instructions,
                direct_data_row_key_encode_local_instructions: execute_phase_attribution
                    .direct_data_row_key_encode_local_instructions,
                direct_data_row_store_get_local_instructions: execute_phase_attribution
                    .direct_data_row_store_get_local_instructions,
                direct_data_row_order_window_local_instructions: execute_phase_attribution
                    .direct_data_row_order_window_local_instructions,
                direct_data_row_page_window_local_instructions: execute_phase_attribution
                    .direct_data_row_page_window_local_instructions,
                grouped_stream_local_instructions: execute_phase_attribution
                    .grouped_stream_local_instructions,
                grouped_fold_local_instructions: execute_phase_attribution
                    .grouped_fold_local_instructions,
                grouped_finalize_local_instructions: execute_phase_attribution
                    .grouped_finalize_local_instructions,
                grouped_count_borrowed_hash_computations: execute_phase_attribution
                    .grouped_count
                    .borrowed_hash_computations,
                grouped_count_bucket_candidate_checks: execute_phase_attribution
                    .grouped_count
                    .bucket_candidate_checks,
                grouped_count_existing_group_hits: execute_phase_attribution
                    .grouped_count
                    .existing_group_hits,
                grouped_count_new_group_inserts: execute_phase_attribution
                    .grouped_count
                    .new_group_inserts,
                grouped_count_row_materialization_local_instructions: execute_phase_attribution
                    .grouped_count
                    .row_materialization_local_instructions,
                grouped_count_group_lookup_local_instructions: execute_phase_attribution
                    .grouped_count
                    .group_lookup_local_instructions,
                grouped_count_existing_group_update_local_instructions: execute_phase_attribution
                    .grouped_count
                    .existing_group_update_local_instructions,
                grouped_count_new_group_insert_local_instructions: execute_phase_attribution
                    .grouped_count
                    .new_group_insert_local_instructions,
                response_decode_local_instructions,
                execute_local_instructions,
                total_local_instructions,
                shared_query_plan_cache_hits: cache_attribution.hits,
                shared_query_plan_cache_misses: cache_attribution.misses,
            },
        ))
    }

    // Execute one typed query through the unified row/grouped result surface so
    // higher layers do not need to branch on grouped shape themselves.
    #[doc(hidden)]
    pub fn execute_query_result<E>(
        &self,
        query: &Query<E>,
    ) -> Result<LoadQueryResult<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        if query.has_grouping() {
            return self
                .execute_grouped(query, None)
                .map(LoadQueryResult::Grouped);
        }

        self.execute_query(query).map(LoadQueryResult::Rows)
    }

    /// Execute one typed delete query and return only the affected-row count.
    #[doc(hidden)]
    pub fn execute_delete_count<E>(&self, query: &Query<E>) -> Result<u32, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        // Phase 1: fail closed if the caller routes a non-delete query here.
        if !query.mode().is_delete() {
            return Err(QueryError::unsupported_query(
                "delete count execution requires delete query mode",
            ));
        }

        // Phase 2: resolve one cached prepared execution-plan contract directly
        // from the shared lower boundary instead of rebuilding it through the
        // typed compiled-query wrapper.
        let (plan, _) = self.cached_prepared_query_plan_for_entity::<E>(query)?;

        // Phase 3: execute the shared delete core while skipping response-row materialization.
        self.with_metrics(|| self.delete_executor::<E>().execute_count(plan))
            .map_err(QueryError::execute)
    }

    /// Execute one scalar query from one pre-built prepared execution contract.
    ///
    /// This is the shared compiled-plan entry boundary used by the typed
    /// `execute_query(...)` surface and adjacent query execution facades.
    pub(in crate::db) fn execute_query_dyn<E>(
        &self,
        mode: QueryMode,
        plan: PreparedExecutionPlan<E>,
    ) -> Result<EntityResponse<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        let result = match mode {
            QueryMode::Load(_) => self.with_metrics(|| self.load_executor::<E>().execute(plan)),
            QueryMode::Delete(_) => self.with_metrics(|| self.delete_executor::<E>().execute(plan)),
        };

        result.map_err(QueryError::execute)
    }

    // Shared load-query terminal wrapper: build plan, run under metrics, map
    // execution errors into query-facing errors.
    pub(in crate::db) fn execute_load_query_with<E, T>(
        &self,
        query: &Query<E>,
        op: impl FnOnce(LoadExecutor<E>, PreparedExecutionPlan<E>) -> Result<T, InternalError>,
    ) -> Result<T, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        let (plan, _) = self.cached_prepared_query_plan_for_entity::<E>(query)?;

        self.with_metrics(|| op(self.load_executor::<E>(), plan))
            .map_err(QueryError::execute)
    }

    // Execute one scalar terminal boundary and keep the executor-specific
    // request/output types contained inside the session adapter.
    fn execute_scalar_terminal_boundary<E>(
        &self,
        query: &Query<E>,
        request: ScalarTerminalBoundaryRequest,
    ) -> Result<ScalarTerminalBoundaryOutput, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, move |load, plan| {
            load.execute_scalar_terminal_request(plan, request)
        })
    }

    // Execute one projection terminal boundary and keep field projection
    // executor details out of fluent query modules.
    fn execute_scalar_projection_boundary<E>(
        &self,
        query: &Query<E>,
        target_field: FieldSlot,
        request: ScalarProjectionBoundaryRequest,
    ) -> Result<ScalarProjectionBoundaryOutput, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, move |load, plan| {
            load.execute_scalar_projection_boundary(plan, target_field, request)
        })
    }

    // Execute one fluent count/exists terminal through a query-owned result
    // shape so fluent terminals do not import executor aggregate outputs.
    pub(in crate::db) fn execute_fluent_existing_rows_terminal<E>(
        &self,
        query: &Query<E>,
        strategy: PreparedFluentExistingRowsTerminalStrategy,
    ) -> Result<FluentScalarTerminalOutput<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        match strategy.into_runtime_request() {
            PreparedFluentExistingRowsTerminalRuntimeRequest::CountRows => self
                .execute_scalar_terminal_boundary(query, ScalarTerminalBoundaryRequest::Count)?
                .into_count()
                .map(FluentScalarTerminalOutput::Count)
                .map_err(QueryError::execute),
            PreparedFluentExistingRowsTerminalRuntimeRequest::ExistsRows => self
                .execute_scalar_terminal_boundary(query, ScalarTerminalBoundaryRequest::Exists)?
                .into_exists()
                .map(FluentScalarTerminalOutput::Exists)
                .map_err(QueryError::execute),
        }
    }

    // Execute one fluent id/extrema terminal through a query-owned result
    // shape after the session adapter has decoded storage keys into typed ids.
    pub(in crate::db) fn execute_fluent_scalar_terminal<E>(
        &self,
        query: &Query<E>,
        strategy: PreparedFluentScalarTerminalStrategy,
    ) -> Result<FluentScalarTerminalOutput<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        let request = match strategy.into_runtime_request() {
            PreparedFluentScalarTerminalRuntimeRequest::IdTerminal { kind } => {
                ScalarTerminalBoundaryRequest::IdTerminal { kind }
            }
            PreparedFluentScalarTerminalRuntimeRequest::IdBySlot { kind, target_field } => {
                ScalarTerminalBoundaryRequest::IdBySlot { kind, target_field }
            }
        };

        self.execute_scalar_terminal_boundary(query, request)?
            .into_id::<E>()
            .map(FluentScalarTerminalOutput::Id)
            .map_err(QueryError::execute)
    }

    // Execute one fluent order-sensitive terminal through the session adapter.
    // The min/max pair request remains distinguished because it returns two ids.
    pub(in crate::db) fn execute_fluent_order_sensitive_terminal<E>(
        &self,
        query: &Query<E>,
        strategy: PreparedFluentOrderSensitiveTerminalStrategy,
    ) -> Result<FluentScalarTerminalOutput<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        match strategy.into_runtime_request() {
            PreparedFluentOrderSensitiveTerminalRuntimeRequest::ResponseOrder { kind } => self
                .execute_scalar_terminal_boundary(
                    query,
                    ScalarTerminalBoundaryRequest::IdTerminal { kind },
                )?
                .into_id::<E>()
                .map(FluentScalarTerminalOutput::Id)
                .map_err(QueryError::execute),
            PreparedFluentOrderSensitiveTerminalRuntimeRequest::NthBySlot { target_field, nth } => {
                self.execute_scalar_terminal_boundary(
                    query,
                    ScalarTerminalBoundaryRequest::NthBySlot { target_field, nth },
                )?
                .into_id::<E>()
                .map(FluentScalarTerminalOutput::Id)
                .map_err(QueryError::execute)
            }
            PreparedFluentOrderSensitiveTerminalRuntimeRequest::MedianBySlot { target_field } => {
                self.execute_scalar_terminal_boundary(
                    query,
                    ScalarTerminalBoundaryRequest::MedianBySlot { target_field },
                )?
                .into_id::<E>()
                .map(FluentScalarTerminalOutput::Id)
                .map_err(QueryError::execute)
            }
            PreparedFluentOrderSensitiveTerminalRuntimeRequest::MinMaxBySlot { target_field } => {
                self.execute_scalar_terminal_boundary(
                    query,
                    ScalarTerminalBoundaryRequest::MinMaxBySlot { target_field },
                )?
                .into_id_pair::<E>()
                .map(FluentScalarTerminalOutput::IdPair)
                .map_err(QueryError::execute)
            }
        }
    }

    // Execute one fluent numeric-field terminal through the session-owned
    // request conversion layer.
    pub(in crate::db) fn execute_fluent_numeric_field_terminal<E>(
        &self,
        query: &Query<E>,
        strategy: PreparedFluentNumericFieldStrategy,
    ) -> Result<Option<Decimal>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        let (target_field, runtime_request) = strategy.into_runtime_parts();
        let request = match runtime_request {
            PreparedFluentNumericFieldRuntimeRequest::Sum => ScalarNumericFieldBoundaryRequest::Sum,
            PreparedFluentNumericFieldRuntimeRequest::SumDistinct => {
                ScalarNumericFieldBoundaryRequest::SumDistinct
            }
            PreparedFluentNumericFieldRuntimeRequest::Avg => ScalarNumericFieldBoundaryRequest::Avg,
            PreparedFluentNumericFieldRuntimeRequest::AvgDistinct => {
                ScalarNumericFieldBoundaryRequest::AvgDistinct
            }
        };

        self.execute_load_query_with(query, move |load, plan| {
            load.execute_numeric_field_boundary(plan, target_field, request)
        })
    }

    // Execute one fluent projection terminal through a query-owned output
    // shape after the session adapter has decoded any data keys into typed ids.
    pub(in crate::db) fn execute_fluent_projection_terminal<E>(
        &self,
        query: &Query<E>,
        strategy: PreparedFluentProjectionStrategy,
    ) -> Result<FluentProjectionTerminalOutput<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        let (target_field, runtime_request) = strategy.into_runtime_parts();

        match runtime_request {
            PreparedFluentProjectionRuntimeRequest::Values => self
                .execute_scalar_projection_boundary(
                    query,
                    target_field,
                    ScalarProjectionBoundaryRequest::Values,
                )?
                .into_values()
                .map(FluentProjectionTerminalOutput::Values)
                .map_err(QueryError::execute),
            PreparedFluentProjectionRuntimeRequest::DistinctValues => self
                .execute_scalar_projection_boundary(
                    query,
                    target_field,
                    ScalarProjectionBoundaryRequest::DistinctValues,
                )?
                .into_values()
                .map(FluentProjectionTerminalOutput::Values)
                .map_err(QueryError::execute),
            PreparedFluentProjectionRuntimeRequest::CountDistinct => self
                .execute_scalar_projection_boundary(
                    query,
                    target_field,
                    ScalarProjectionBoundaryRequest::CountDistinct,
                )?
                .into_count()
                .map(FluentProjectionTerminalOutput::Count)
                .map_err(QueryError::execute),
            PreparedFluentProjectionRuntimeRequest::ValuesWithIds => self
                .execute_scalar_projection_boundary(
                    query,
                    target_field,
                    ScalarProjectionBoundaryRequest::ValuesWithIds,
                )?
                .into_values_with_ids::<E>()
                .map(FluentProjectionTerminalOutput::ValuesWithIds)
                .map_err(QueryError::execute),
            PreparedFluentProjectionRuntimeRequest::TerminalValue { terminal_kind } => self
                .execute_scalar_projection_boundary(
                    query,
                    target_field,
                    ScalarProjectionBoundaryRequest::TerminalValue { terminal_kind },
                )?
                .into_terminal_value()
                .map(FluentProjectionTerminalOutput::TerminalValue)
                .map_err(QueryError::execute),
        }
    }

    // Execute the fluent `bytes()` terminal without leaking `LoadExecutor`
    // closure assembly into query fluent code.
    pub(in crate::db) fn execute_fluent_bytes<E>(&self, query: &Query<E>) -> Result<u64, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, |load, plan| load.bytes(plan))
    }

    // Execute the fluent `bytes_by(field)` terminal at the session boundary.
    pub(in crate::db) fn execute_fluent_bytes_by_slot<E>(
        &self,
        query: &Query<E>,
        target_slot: FieldSlot,
    ) -> Result<u64, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, move |load, plan| {
            load.bytes_by_slot(plan, target_slot)
        })
    }

    // Execute the fluent `take(k)` terminal at the session boundary.
    pub(in crate::db) fn execute_fluent_take<E>(
        &self,
        query: &Query<E>,
        take_count: u32,
    ) -> Result<EntityResponse<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, move |load, plan| load.take(plan, take_count))
    }

    // Execute one row-returning fluent top/bottom-k terminal at the session boundary.
    pub(in crate::db) fn execute_fluent_ranked_rows_by_slot<E>(
        &self,
        query: &Query<E>,
        target_slot: FieldSlot,
        take_count: u32,
        descending: bool,
    ) -> Result<EntityResponse<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, move |load, plan| {
            if descending {
                load.top_k_by_slot(plan, target_slot, take_count)
            } else {
                load.bottom_k_by_slot(plan, target_slot, take_count)
            }
        })
    }

    // Execute one value-returning fluent top/bottom-k terminal at the session boundary.
    pub(in crate::db) fn execute_fluent_ranked_values_by_slot<E>(
        &self,
        query: &Query<E>,
        target_slot: FieldSlot,
        take_count: u32,
        descending: bool,
    ) -> Result<Vec<Value>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, move |load, plan| {
            if descending {
                load.top_k_by_values_slot(plan, target_slot, take_count)
            } else {
                load.bottom_k_by_values_slot(plan, target_slot, take_count)
            }
        })
    }

    // Execute one id/value-returning fluent top/bottom-k terminal at the session boundary.
    pub(in crate::db) fn execute_fluent_ranked_values_with_ids_by_slot<E>(
        &self,
        query: &Query<E>,
        target_slot: FieldSlot,
        take_count: u32,
        descending: bool,
    ) -> Result<Vec<(Id<E>, Value)>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_load_query_with(query, move |load, plan| {
            if descending {
                load.top_k_by_with_ids_slot(plan, target_slot, take_count)
            } else {
                load.bottom_k_by_with_ids_slot(plan, target_slot, take_count)
            }
        })
    }

    /// Build one trace payload for a query without executing it.
    ///
    /// This lightweight surface is intended for developer diagnostics:
    /// plan hash, access strategy summary, and planner/executor route shape.
    pub fn trace_query<E>(&self, query: &Query<E>) -> Result<QueryTracePlan, QueryError>
    where
        E: EntityKind<Canister = C>,
    {
        let visibility = self.query_plan_visibility_for_store_path(E::Store::PATH)?;
        let visible_indexes = Self::visible_indexes_for_model(E::MODEL, visibility);
        let (prepared_plan, cache_attribution) =
            self.cached_prepared_query_plan_for_entity::<E>(query)?;
        let logical_plan = prepared_plan.logical_plan();
        let explain = logical_plan.explain();
        let plan_hash = query.plan_hash_hex_with_visible_indexes(&visible_indexes)?;
        let executable_access = prepared_plan.access().executable_contract();
        let access_strategy = summarize_executable_access_plan(&executable_access);
        let execution_family = match query.mode() {
            QueryMode::Load(_) => Some(trace_execution_family_from_executor(
                prepared_plan
                    .execution_family()
                    .map_err(QueryError::execute)?,
            )),
            QueryMode::Delete(_) => None,
        };
        let reuse = query_plan_cache_reuse_event(cache_attribution);

        Ok(QueryTracePlan::new(
            plan_hash,
            access_strategy,
            execution_family,
            reuse,
            explain,
        ))
    }

    /// Execute one scalar paged load query and return optional continuation cursor plus trace.
    pub(crate) fn execute_load_query_paged_with_trace<E>(
        &self,
        query: &Query<E>,
        cursor_token: Option<&str>,
    ) -> Result<PagedLoadExecutionWithTrace<E>, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        // Phase 1: build/validate prepared execution plan and reject grouped plans.
        let plan = self.cached_prepared_query_plan_for_entity::<E>(query)?.0;
        Self::ensure_scalar_paged_execution_family(
            plan.execution_family().map_err(QueryError::execute)?,
        )?;

        // Phase 2: decode external cursor token and validate it against plan surface.
        let cursor_bytes = decode_optional_cursor_token(cursor_token)
            .map_err(QueryError::from_cursor_plan_error)?;
        let cursor = plan
            .prepare_cursor(cursor_bytes.as_deref())
            .map_err(query_error_from_executor_plan_error)?;

        // Phase 3: execute one traced page and encode outbound continuation token.
        let (page, trace) = self
            .with_metrics(|| {
                self.load_executor::<E>()
                    .execute_paged_with_cursor_traced(plan, cursor)
            })
            .map_err(QueryError::execute)?;
        finalize_scalar_paged_execution(page, trace)
    }

    /// Execute one grouped query page with optional grouped continuation cursor.
    ///
    /// This is the explicit grouped execution boundary; scalar load APIs reject
    /// grouped plans to preserve scalar response contracts.
    pub(in crate::db) fn execute_grouped<E>(
        &self,
        query: &Query<E>,
        cursor_token: Option<&str>,
    ) -> Result<PagedGroupedExecutionWithTrace, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        // Phase 1: build the prepared execution plan once from the typed query.
        let plan = self.cached_prepared_query_plan_for_entity::<E>(query)?.0;

        // Phase 2: reuse the shared prepared grouped execution path and then
        // finalize the outward grouped payload at the session boundary.
        let (page, trace) = self.execute_grouped_plan_with_trace(plan, cursor_token)?;

        Self::finalize_grouped_execution_page(page, trace)
    }

    // Execute one grouped prepared plan page with optional grouped cursor
    // while letting the caller choose the final grouped-runtime dispatch.
    fn execute_grouped_plan_with<E, T>(
        &self,
        plan: PreparedExecutionPlan<E>,
        cursor_token: Option<&str>,
        op: impl FnOnce(
            LoadExecutor<E>,
            PreparedExecutionPlan<E>,
            crate::db::cursor::GroupedPlannedCursor,
        ) -> Result<T, InternalError>,
    ) -> Result<T, QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        // Phase 1: validate the prepared plan shape before decoding cursors.
        Self::ensure_grouped_execution_family(
            plan.execution_family().map_err(QueryError::execute)?,
        )?;

        // Phase 2: decode external grouped cursor token and validate against plan.
        let cursor = decode_optional_grouped_cursor_token(cursor_token)
            .map_err(QueryError::from_cursor_plan_error)?;
        let cursor = plan
            .prepare_grouped_cursor_token(cursor)
            .map_err(query_error_from_executor_plan_error)?;

        // Phase 3: execute one grouped page while preserving the structural
        // grouped cursor payload for whichever outward cursor format the caller needs.
        self.with_metrics(|| op(self.load_executor::<E>(), plan, cursor))
            .map_err(QueryError::execute)
    }

    // Execute one grouped prepared plan page with optional grouped cursor.
    fn execute_grouped_plan_with_trace<E>(
        &self,
        plan: PreparedExecutionPlan<E>,
        cursor_token: Option<&str>,
    ) -> Result<(GroupedCursorPage, Option<ExecutionTrace>), QueryError>
    where
        E: PersistedRow<Canister = C> + EntityValue,
    {
        self.execute_grouped_plan_with(plan, cursor_token, |executor, plan, cursor| {
            executor.execute_grouped_paged_with_cursor_traced(plan, cursor)
        })
    }
}