uqa-engine 0.3.6

Engine: schema-aware table store, catalog restore, transactions
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//
// Unified Query Algebra
//
// Copyright (c) 2023-2026 Cognica, Inc.
//

//! Refresh only the dependencies changed in a pinned durable snapshot.

use std::collections::{BTreeMap, BTreeSet};
use std::sync::atomic::Ordering;

use uqa_storage::{CatalogCacheRevisions, StorageBackendError, StorageBackendResult};

use super::Engine;

fn changed_names(
    previous: &BTreeMap<String, u64>,
    current: &BTreeMap<String, u64>,
) -> BTreeSet<String> {
    previous
        .keys()
        .chain(current.keys())
        .filter(|name| previous.get(*name) != current.get(*name))
        .cloned()
        .collect()
}

impl Engine {
    /// An epoch may be published after the physical commit was already seen.
    /// Reconcile against the durable generations rather than decoding again.
    pub(super) fn refresh_tracked_storage_snapshot(&self) -> StorageBackendResult<bool> {
        if self.epochs.storage_cache_revisions.lock().is_none() {
            return Ok(false);
        }
        let Some(backend) = self.storage.backend.as_ref() else {
            return Ok(false);
        };
        let _statement = self.runtime.statement_gate.lock();
        let _refresh = self.epochs.external_commit_refresh.lock();
        if backend.in_transaction() {
            return Ok(false);
        }
        backend.begin_read_transaction()?;
        let result = self.refresh_pinned_transaction_snapshot();
        let cleanup = backend.rollback_transaction();
        match (result, cleanup) {
            (Ok(()), Ok(())) => Ok(true),
            (Err(error), Ok(())) | (Ok(()), Err(error)) => Err(error),
            (Err(error), Err(cleanup)) => Err(StorageBackendError::Other(format!(
                "cache refresh failed: {error}; snapshot cleanup failed: {cleanup}"
            ))),
        }
    }

    pub(super) fn refresh_tracked_pinned_snapshot(
        &self,
        catalog_epoch: u64,
        data_epoch: u64,
        registry_epoch: u64,
    ) -> StorageBackendResult<bool> {
        let Some(catalog) = self.storage.catalog.as_ref() else {
            return Ok(false);
        };
        let Some(current) = catalog.cache_revisions()? else {
            return Ok(false);
        };
        let previous = self.epochs.storage_cache_revisions.lock().clone();
        let catalog_changed = previous.as_ref().is_none_or(|previous| {
            previous.table_catalog != current.table_catalog
                || previous.storage_schema != current.storage_schema
        });
        let registries_changed = catalog_changed
            || previous
                .as_ref()
                .is_none_or(|previous| previous.registries != current.registries);
        if catalog_changed {
            self.clear_persistent_table_bindings_for_catalog_reload();
            self.reload_table_catalog(catalog_epoch)?;
            self.synchronize_partition_identity_watermarks()?;
        }
        if registries_changed {
            self.reload_catalog_registries(registry_epoch)?;
        } else if let Some(graphs) = current.graphs.as_ref() {
            let changed = self.refresh_graph_handles(
                catalog.as_ref(),
                previous
                    .as_ref()
                    .and_then(|previous| previous.graphs.as_ref()),
                graphs,
            )?;
            if !changed.is_empty() {
                // Graph namespaces and AGE label relations also appear in
                // regnamespace/regclass output, independently of SQL DDL.
                self.clear_regtype_output_cache();
            }
            self.refresh_changed_graph_path_indexes(catalog.as_ref(), &changed)?;
        }
        // Physical indexes and analyzer bindings belong to the same committed revision. Restore changed registries before reopening data stores, so an old cached binding never meets newly committed occurrence metadata.
        if !catalog_changed {
            if let Some(previous) = previous.as_ref() {
                self.refresh_changed_table_caches(previous, &current)?;
            }
        }
        // Generations become observed only after every dependent cache was
        // restored successfully. An error leaves the snapshot eligible to retry.
        self.epochs
            .table_catalog
            .seen
            .store(catalog_epoch, Ordering::Release);
        self.epochs
            .table_data
            .seen
            .store(data_epoch, Ordering::Release);
        self.epochs
            .catalog_registry
            .seen
            .store(registry_epoch, Ordering::Release);
        if previous.as_ref() != Some(&current) {
            self.clear_sql_statement_cache();
            self.clear_bayesian_params_cache();
            self.invalidate_prepared_plans();
        }
        *self.epochs.storage_cache_revisions.lock() = Some(current);
        Ok(true)
    }

    fn refresh_changed_table_caches(
        &self,
        previous: &CatalogCacheRevisions,
        current: &CatalogCacheRevisions,
    ) -> StorageBackendResult<()> {
        let data = changed_names(&previous.table_data, &current.table_data);
        let statistics = changed_names(&previous.column_statistics, &current.column_statistics);
        let maintenance = changed_names(
            &previous.statistics_maintenance,
            &current.statistics_maintenance,
        );
        let names = data
            .iter()
            .chain(&statistics)
            .chain(&maintenance)
            .cloned()
            .collect::<BTreeSet<_>>();
        let catalog = self
            .storage
            .catalog
            .as_ref()
            .expect("tracked persistent catalog");
        let private_snapshot = self
            .storage
            .backend
            .as_ref()
            .map(|backend| backend.transaction_has_written())
            .transpose()?
            .unwrap_or(false);
        let mut partition_watermarks_changed = false;
        for name in names {
            let relation = uqa_storage::RelationIdentity::from_legacy_name(&name)
                .map_err(StorageBackendError::Other)?;
            let table = self.storage.tables.read().get(&relation).cloned();
            let Some(table) = table else {
                continue;
            };
            if table.persistence == uqa_sql::ast::RelationPersistence::Temporary {
                continue;
            }
            if data.contains(&name) {
                self.rebind_persistent_table_stores(&name, &table)?;
                self.refresh_table_next_id(&name, &table)?;
                table.doc_count_dirty.store(true, Ordering::Release);
                let hierarchy = table.hierarchy.read();
                partition_watermarks_changed |= (hierarchy.partition_spec.is_some()
                    || hierarchy.is_partition())
                    && table.columns.read().iter().any(|column| {
                        column
                            .auto_increment
                            .as_ref()
                            .is_some_and(uqa_sql::ast::AutoIncrement::is_legacy)
                    });
            }
            if statistics.contains(&name) {
                let load = || Self::load_column_stats_from_catalog(catalog.as_ref(), &name);
                // A private transaction may reuse a durable counter value
                // after rollback. Never publish its payload to sibling sessions.
                let stats = if private_snapshot {
                    std::sync::Arc::new(load()?)
                } else {
                    self.statistics.statistics_snapshots.load(
                        &name,
                        table.object_id(),
                        current
                            .column_statistics
                            .get(&name)
                            .copied()
                            .unwrap_or_default(),
                        load,
                    )?
                };
                table.column_stats.restore(&stats);
                table.column_stats_loaded.store(true, Ordering::Release);
            }
            let dirty = (table.column_stats.read().is_empty() && !table.columns.read().is_empty())
                || crate::statistics::MaintenanceState::load_for(
                    catalog.as_ref(),
                    &name,
                    table.object_id(),
                )?
                .invalidates_existing_statistics();
            table.column_stats_dirty.store(dirty, Ordering::Release);
        }
        if partition_watermarks_changed {
            self.synchronize_partition_identity_watermarks()?;
        }
        Ok(())
    }
}