mentatdb 1.16.0

// Copyright 2016-2018 Mozilla
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
// this file except in compliance with the License. You may obtain a copy of the
// License at http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software distributed
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.

#![allow(dead_code)]

use std::borrow::Borrow;

use std::collections::BTreeMap;

use std::sync::{Arc, Mutex};

use rusqlite::TransactionBehavior;

pub use core_traits::{Attribute, Entid, KnownEntid, StructuredMap, TypedValue, ValueType};

use mentat_core::{HasSchema, Keyword, Schema, TxReport, ValueRc};

use mentat_db::cache::{InProgressSQLiteAttributeCache, SQLiteAttributeCache};

use mentat_db::db;
use mentat_db::{
    InProgressObserverTransactWatcher, PartitionMap, TxObservationService, TxObserver,
};

use mentat_query_pull::{pull_attributes_for_entities, pull_attributes_for_entity};

use mentat_transaction::{CacheAction, CacheDirection, InProgress, InProgressRead, Metadata};

use public_traits::errors::{MentatError, Result};

use mentat_transaction::query::{
    lookup_value_for_attribute, lookup_values_for_attribute, q_explain, q_once, q_prepare,
    q_uncached, Known, PreparedResult, QueryExplanation, QueryInputs, QueryOutput,
};

/// A mutable, safe reference to the current Mentat store.
pub struct Conn {
    /// `Mutex` since all reads and writes need to be exclusive.  Internally, owned data for the
    /// volatile parts (generation and partition map), and `Arc` for the infrequently changing parts
    /// (schema, cache) that we want to share across threads.  A consuming thread may use a shared
    /// reference after the `Conn`'s `Metadata` has moved on.
    ///
    /// The motivating case is multiple query threads taking references to the current schema to
    /// perform long-running queries while a single writer thread moves the metadata -- partition
    /// map and schema -- forward.
    ///
    /// We want the attribute cache to be isolated across transactions, updated within
    /// `InProgress` writes, and updated in the `Conn` on commit. To achieve this we
    /// store the cache itself in an `Arc` inside `SQLiteAttributeCache`, so that `.get_mut()`
    /// gives us copy-on-write semantics.
    /// We store that cached `Arc` here in a `Mutex`, so that the main copy can be carefully
    /// replaced on commit.
    metadata: Mutex<Metadata>,

    // TODO: maintain set of change listeners or handles to transaction report queues. #298.

    // TODO: maintain cache of query plans that could be shared across threads and invalidated when
    // the schema changes. #315.
    pub(crate) tx_observer_service: Mutex<TxObservationService>,
}

impl Conn {
    // Intentionally not public.
    fn new(partition_map: PartitionMap, schema: Schema) -> Conn {
        Conn {
            metadata: Mutex::new(Metadata::new(
                0,
                partition_map,
                Arc::new(schema),
                Default::default(),
            )),
            tx_observer_service: Mutex::new(TxObservationService::new()),
        }
    }

    /// Take the metadata lock, recovering it if an earlier panic poisoned it.
    ///
    /// Nothing that can fail (SQL, projection) runs while the lock is held: readers
    /// take a [`Conn::snapshot`] and release it, and `InProgress::commit` only swaps
    /// in already-computed values. So a poisoned lock still guards consistent data.
    fn lock_metadata(&self) -> std::sync::MutexGuard<'_, Metadata> {
        self.metadata
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
    }

    /// The current schema and attribute cache, both cheap `Arc` clones, taken
    /// under the lock and released before any query runs. An interrupted or
    /// failing query therefore never holds (or poisons) the metadata lock.
    fn snapshot(&self) -> (Arc<Schema>, SQLiteAttributeCache) {
        let m = self.lock_metadata();
        (m.schema.clone(), m.attribute_cache.clone())
    }

    pub fn connect(sqlite: &mut rusqlite::Connection) -> Result<Conn> {
        let db = db::ensure_current_version(sqlite)?;
        Ok(Conn::new(db.partition_map, db.schema))
    }

    /// Yield a clone of the current `Schema` instance.
    pub fn current_schema(&self) -> Arc<Schema> {
        // We always unwrap the mutex lock: if it's poisoned, this will propogate panics to all
        // accessing threads.  This is perhaps not reasonable; we expect the mutex to be held for
        // very short intervals, but a panic during a critical update section is possible, since the
        // lock encapsulates committing a SQL transaction.
        //
        // That being said, in the future we will provide an interface to take the mutex, providing
        // maximum flexibility for Mentat consumers.
        //
        // This approach might need to change when we support interrupting query threads (#297), and
        // will definitely need to change if we support interrupting transactor threads.
        //
        // Improving this is tracked by https://github.com/mozilla/mentat/issues/356.
        self.lock_metadata().schema.clone()
    }

    pub fn current_cache(&self) -> SQLiteAttributeCache {
        self.lock_metadata().attribute_cache.clone()
    }

    pub fn last_tx_id(&self) -> Entid {
        // The mutex is taken during this entire method.
        let metadata = self.lock_metadata();

        metadata.partition_map[":db.part/tx"].next_entid() - 1
    }

    /// Query the Mentat store, using the given connection and the current metadata.
    pub fn q_once<T>(
        &self,
        sqlite: &rusqlite::Connection,
        query: &str,
        inputs: T,
    ) -> Result<QueryOutput>
    where
        T: Into<Option<QueryInputs>>,
    {
        // Doesn't clone, unlike `current_schema`.
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        q_once(sqlite, known, query, inputs)
    }

    /// `q_once`, plus the attributes it filtered by value (see `auto_index`).
    pub fn q_once_value_filtered<T>(
        &self,
        sqlite: &rusqlite::Connection,
        query: &str,
        inputs: T,
    ) -> Result<(QueryOutput, std::collections::BTreeSet<Entid>)>
    where
        T: Into<Option<QueryInputs>>,
    {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        mentat_transaction::query::q_once_value_filtered(sqlite, known, query, inputs)
    }

    /// Query the store against a historical basis reconstructed as of transaction
    /// `tx` (inclusive): the value that was current at `tx`.
    pub fn q_once_as_of<T>(
        &self,
        sqlite: &rusqlite::Connection,
        query: &str,
        inputs: T,
        tx: Entid,
    ) -> Result<QueryOutput>
    where
        T: Into<Option<QueryInputs>>,
    {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        mentat_transaction::query::q_once_temporal(
            sqlite,
            known,
            query,
            inputs,
            mentat_query_algebrizer::TemporalBound::AsOf(tx),
        )
    }

    /// Query the store seeing only datoms transacted after transaction `tx`
    /// (`since`).
    pub fn q_once_since<T>(
        &self,
        sqlite: &rusqlite::Connection,
        query: &str,
        inputs: T,
        tx: Entid,
    ) -> Result<QueryOutput>
    where
        T: Into<Option<QueryInputs>>,
    {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        mentat_transaction::query::q_once_temporal(
            sqlite,
            known,
            query,
            inputs,
            mentat_query_algebrizer::TemporalBound::Since(tx),
        )
    }

    /// Query the Mentat store, using the given connection and the current metadata,
    /// but without using the cache.
    pub fn q_uncached<T>(
        &self,
        sqlite: &rusqlite::Connection,
        query: &str,
        inputs: T,
    ) -> Result<QueryOutput>
    where
        T: Into<Option<QueryInputs>>,
    {
        let (schema, _) = self.snapshot();
        q_uncached(sqlite, &schema, query, inputs)
    }

    pub fn q_prepare<'sqlite, T>(
        &self,
        sqlite: &'sqlite rusqlite::Connection,
        query: &str,
        inputs: T,
    ) -> PreparedResult<'sqlite>
    where
        T: Into<Option<QueryInputs>>,
    {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        q_prepare(sqlite, known, query, inputs)
    }

    pub fn q_explain<T>(
        &self,
        sqlite: &rusqlite::Connection,
        query: &str,
        inputs: T,
    ) -> Result<QueryExplanation>
    where
        T: Into<Option<QueryInputs>>,
    {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        q_explain(sqlite, known, query, inputs)
    }

    /// `q_explain` against a historical basis (`None` = current).
    pub fn q_explain_temporal<T>(
        &self,
        sqlite: &rusqlite::Connection,
        query: &str,
        inputs: T,
        temporal: Option<mentat_query_algebrizer::TemporalBound>,
    ) -> Result<QueryExplanation>
    where
        T: Into<Option<QueryInputs>>,
    {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        mentat_transaction::query::q_explain_temporal(sqlite, known, query, inputs, temporal)
    }

    pub fn pull_attributes_for_entities<E, A>(
        &self,
        sqlite: &rusqlite::Connection,
        entities: E,
        attributes: A,
    ) -> Result<BTreeMap<Entid, ValueRc<StructuredMap>>>
    where
        E: IntoIterator<Item = Entid>,
        A: IntoIterator<Item = Entid>,
    {
        let (schema, _) = self.snapshot();
        pull_attributes_for_entities(&schema, &mentat_sql::sqlite(sqlite), entities, attributes)
            .map_err(|e| e.into())
    }

    pub fn pull_attributes_for_entity<A>(
        &self,
        sqlite: &rusqlite::Connection,
        entity: Entid,
        attributes: A,
    ) -> Result<StructuredMap>
    where
        A: IntoIterator<Item = Entid>,
    {
        let (schema, _) = self.snapshot();
        pull_attributes_for_entity(&schema, &mentat_sql::sqlite(sqlite), entity, attributes)
            .map_err(|e| e.into())
    }

    pub fn lookup_values_for_attribute(
        &self,
        sqlite: &rusqlite::Connection,
        entity: Entid,
        attribute: &edn::Keyword,
    ) -> Result<Vec<TypedValue>> {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        lookup_values_for_attribute(sqlite, known, entity, attribute)
    }

    pub fn lookup_value_for_attribute(
        &self,
        sqlite: &rusqlite::Connection,
        entity: Entid,
        attribute: &edn::Keyword,
    ) -> Result<Option<TypedValue>> {
        let (schema, cache) = self.snapshot();
        let known = Known::new(&schema, Some(&cache));
        lookup_value_for_attribute(sqlite, known, entity, attribute)
    }

    /// Take a SQLite transaction.
    fn begin_transaction_with_behavior<'m, 'conn>(
        &'m mut self,
        sqlite: &'conn mut rusqlite::Connection,
        behavior: TransactionBehavior,
    ) -> Result<InProgress<'m, 'conn>> {
        let tx = sqlite.transaction_with_behavior(behavior)?;
        let (current_generation, current_partition_map, current_schema, cache_cow) = {
            // The mutex is taken during this block.
            let current: &Metadata = &self.lock_metadata();
            (
                current.generation,
                // Expensive, but the partition map is updated after every committed transaction.
                current.partition_map.clone(),
                // Cheap.
                current.schema.clone(),
                current.attribute_cache.clone(),
            )
        };

        Ok(InProgress {
            mutex: &self.metadata,
            transaction: tx,
            generation: current_generation,
            partition_map: current_partition_map,
            schema: (*current_schema).clone(),
            cache: InProgressSQLiteAttributeCache::from_cache(cache_cow),
            use_caching: true,
            tx_observer: &self.tx_observer_service,
            tx_observer_watcher: InProgressObserverTransactWatcher::new(),
        })
    }

    // Helper to avoid passing connections around.
    // Make both args mutable so that we can't have parallel access.
    pub fn begin_read<'m, 'conn>(
        &'m mut self,
        sqlite: &'conn mut rusqlite::Connection,
    ) -> Result<InProgressRead<'m, 'conn>> {
        self.begin_transaction_with_behavior(sqlite, TransactionBehavior::Deferred)
            .map(|ip| InProgressRead { in_progress: ip })
    }

    pub fn begin_uncached_read<'m, 'conn>(
        &'m mut self,
        sqlite: &'conn mut rusqlite::Connection,
    ) -> Result<InProgressRead<'m, 'conn>> {
        self.begin_transaction_with_behavior(sqlite, TransactionBehavior::Deferred)
            .map(|mut ip| {
                ip.use_caching(false);
                InProgressRead { in_progress: ip }
            })
    }

    /// IMMEDIATE means 'start the transaction now, but don't exclude readers'. It prevents other
    /// connections from taking immediate or exclusive transactions. This is appropriate for our
    /// writes and `InProgress`: it means we are ready to write whenever we want to, and nobody else
    /// can start a transaction that's not `DEFERRED`, but we don't need exclusivity yet.
    pub fn begin_transaction<'m, 'conn>(
        &'m mut self,
        sqlite: &'conn mut rusqlite::Connection,
    ) -> Result<InProgress<'m, 'conn>> {
        self.begin_transaction_with_behavior(sqlite, TransactionBehavior::Immediate)
    }

    /// Transact entities against the Mentat store, using the given connection and the current
    /// metadata.
    pub fn transact<B>(
        &mut self,
        sqlite: &mut rusqlite::Connection,
        transaction: B,
    ) -> Result<TxReport>
    where
        B: Borrow<str>,
    {
        // Parse outside the SQL transaction. This is a tradeoff: we are limiting the scope of the
        // transaction, and indeed we don't even create a SQL transaction if the provided input is
        // invalid, but it means SQLite errors won't be found until the parse is complete, and if
        // there's a race for the database (don't do that!) we are less likely to win it.
        let entities = edn::parse::entities(transaction.borrow())?;

        let mut in_progress = self.begin_transaction(sqlite)?;
        let report = in_progress.transact_entities(entities)?;
        in_progress.commit()?;

        Ok(report)
    }

    /// Speculatively transact `transaction` and return its `TxReport` without
    /// persisting anything (Datomic `d/with` / pg_mentat `mentat.with`). The
    /// enclosing SQLite transaction is rolled back on drop, so no changes are
    /// committed even though a real IMMEDIATE transaction was opened.
    pub fn transact_speculative<B>(
        &mut self,
        sqlite: &mut rusqlite::Connection,
        transaction: B,
    ) -> Result<TxReport>
    where
        B: Borrow<str>,
    {
        let entities = edn::parse::entities(transaction.borrow())?;

        let mut in_progress = self.begin_transaction(sqlite)?;
        let report = in_progress.transact_entities_speculative(entities)?;
        // Deliberately do NOT commit: drop rolls back the outer transaction.
        drop(in_progress);

        Ok(report)
    }

    /// Adds or removes the values of a given attribute to an in-memory cache.
    /// The attribute should be a namespaced string: e.g., `:foo/bar`.
    /// `cache_action` determines if the attribute should be added or removed from the cache.
    /// CacheAction::Add is idempotent - each attribute is only added once.
    /// CacheAction::Remove throws an error if the attribute does not currently exist in the cache.
    pub fn cache(
        &mut self,
        sqlite: &mut rusqlite::Connection,
        schema: &Schema,
        attribute: &Keyword,
        cache_direction: CacheDirection,
        cache_action: CacheAction,
    ) -> Result<()> {
        let mut metadata = self.lock_metadata();
        let attribute_entid: Entid;

        // Immutable borrow of metadata.
        {
            attribute_entid = metadata
                .schema
                .attribute_for_ident(attribute)
                .ok_or_else(|| MentatError::UnknownAttribute(attribute.to_string()))?
                .1
                .into();
        }

        let cache = &mut metadata.attribute_cache;
        match cache_action {
            CacheAction::Register => match cache_direction {
                CacheDirection::Both => cache.register(schema, sqlite, attribute_entid),
                CacheDirection::Forward => cache.register_forward(schema, sqlite, attribute_entid),
                CacheDirection::Reverse => cache.register_reverse(schema, sqlite, attribute_entid),
            }
            .map_err(|e| e.into()),
            CacheAction::Deregister => {
                cache.unregister(attribute_entid);
                Ok(())
            }
        }
    }

    pub fn register_observer(&mut self, key: String, observer: Arc<TxObserver>) {
        self.tx_observer_service
            .lock()
            .unwrap()
            .register(key, observer);
    }

    pub fn unregister_observer(&mut self, key: &str) {
        self.tx_observer_service.lock().unwrap().deregister(key);
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use std::time::Instant;

    use core_traits::{Binding, TypedValue};

    use mentat_core::CachedAttributes;

    use mentat_transaction::query::Variable;

    use mentat_transaction::query::{IntoResult, QueryInputs, QueryResults};

    use mentat_db::USER0;

    use mentat_transaction::Queryable;

    #[test]
    fn test_transact_does_not_collide_existing_entids() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();

        // Let's find out the next ID that'll be allocated. We're going to try to collide with it
        // a bit later.
        let next =
            conn.metadata.lock().expect("metadata").partition_map[":db.part/user"].next_entid();
        let t = format!("[[:db/add {} :db.schema/attribute \"tempid\"]]", next + 1);

        match conn.transact(&mut sqlite, t.as_str()) {
            Err(MentatError::DbError(e)) => {
                assert_eq!(
                    e.kind(),
                    ::db_traits::errors::DbErrorKind::UnallocatedEntid(next + 1)
                );
            }
            x => panic!("expected db error, got {:?}", x),
        }

        // Transact two more tempids.
        let t = "[[:db/add \"one\" :db.schema/attribute \"more\"]]";
        let report = conn.transact(&mut sqlite, t).expect("transact succeeded");
        assert_eq!(report.tempids["more"], next);
        assert_eq!(report.tempids["one"], next + 1);
    }

    #[test]
    fn test_transact_does_not_collide_new_entids() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();

        // Let's find out the next ID that'll be allocated. We're going to try to collide with it.
        let next =
            conn.metadata.lock().expect("metadata").partition_map[":db.part/user"].next_entid();

        // If this were to be resolved, we'd get [:db/add 65537 :db.schema/attribute 65537], but
        // we should reject this, because the first ID was provided by the user!
        let t = format!("[[:db/add {} :db.schema/attribute \"tempid\"]]", next);

        match conn.transact(&mut sqlite, t.as_str()) {
            Err(MentatError::DbError(e)) => {
                // All this, despite this being the ID we were about to allocate!
                assert_eq!(
                    e.kind(),
                    ::db_traits::errors::DbErrorKind::UnallocatedEntid(next)
                );
            }
            x => panic!("expected db error, got {:?}", x),
        }

        // And if we subsequently transact in a way that allocates one ID, we _will_ use that one.
        // Note that `10` is a bootstrapped entid; we use it here as a known-good value.
        let t = "[[:db/add 10 :db.schema/attribute \"temp\"]]";
        let report = conn.transact(&mut sqlite, t).expect("transact succeeded");
        assert_eq!(report.tempids["temp"], next);
    }

    /// Return the entid that will be allocated to the next transacted tempid.
    fn get_next_entid(conn: &Conn) -> Entid {
        let partition_map = &conn.metadata.lock().unwrap().partition_map;
        partition_map.get(":db.part/user").unwrap().next_entid()
    }

    #[test]
    fn test_compound_transact() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();

        let tempid_offset = get_next_entid(&conn);

        let t = "[[:db/add \"one\" :db/ident :a/keyword1] \
                 [:db/add \"two\" :db/ident :a/keyword2]]";

        // This can refer to `t`, 'cos they occur in separate txes.
        let t2 = "[{:db.schema/attribute \"three\", :db/ident :a/keyword1}]";

        // Scoped borrow of `conn`.
        {
            let mut in_progress = conn
                .begin_transaction(&mut sqlite)
                .expect("begun successfully");
            let report = in_progress.transact(t).expect("transacted successfully");
            let one = *report.tempids.get("one").expect("found one");
            let two = *report.tempids.get("two").expect("found two");
            assert!(one != two);
            assert!(one == tempid_offset || one == tempid_offset + 1);
            assert!(two == tempid_offset || two == tempid_offset + 1);

            println!(
                "RES: {:?}",
                in_progress
                    .q_once("[:find ?v :where [?x :db/ident ?v]]", None)
                    .unwrap()
            );

            let during = in_progress
                .q_once("[:find ?x . :where [?x :db/ident :a/keyword1]]", None)
                .expect("query succeeded");
            assert_eq!(
                during.results,
                QueryResults::Scalar(Some(TypedValue::Ref(one).into()))
            );

            let report = in_progress.transact(t2).expect("t2 succeeded");
            in_progress.commit().expect("commit succeeded");
            let three = *report.tempids.get("three").expect("found three");
            assert!(one != three);
            assert!(two != three);
        }

        // The DB part table changed.
        let tempid_offset_after = get_next_entid(&conn);
        assert_eq!(tempid_offset + 3, tempid_offset_after);
    }

    #[test]
    fn test_transact_speculative() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();

        let before = get_next_entid(&conn);

        // Speculatively add an ident. The report should reflect the change...
        let t = "[[:db/add \"e\" :db/ident :spec/keyword]]";
        let report = conn
            .transact_speculative(&mut sqlite, t)
            .expect("speculative transact succeeded");
        let e = *report.tempids.get("e").expect("tempid resolved");
        assert_eq!(e, before, "speculative report allocates the next entid");

        // ...but nothing is persisted: the ident is not in the store.
        let found = conn
            .q_once(
                &mut sqlite,
                "[:find ?x . :where [?x :db/ident :spec/keyword]]",
                None,
            )
            .expect("query succeeded");
        assert_eq!(
            found.results,
            QueryResults::Scalar(None),
            "speculative datom must not persist"
        );

        // ...and the partition counter was rolled back, so a *real* transact
        // reuses the same entid the speculative run reported.
        assert_eq!(get_next_entid(&conn), before, "entid not consumed");
        let real = conn
            .transact(&mut sqlite, t)
            .expect("real transact succeeded");
        assert_eq!(*real.tempids.get("e").expect("tempid"), before);
        assert_eq!(get_next_entid(&conn), before + 1);
    }

    #[test]
    fn test_simple_prepared_query() {
        let mut c = db::new_connection("").expect("Couldn't open conn.");
        let mut conn = Conn::connect(&mut c).expect("Couldn't open DB.");
        conn.transact(
            &mut c,
            r#"[
            [:db/add "s" :db/ident :foo/boolean]
            [:db/add "s" :db/valueType :db.type/boolean]
            [:db/add "s" :db/cardinality :db.cardinality/one]
        ]"#,
        )
        .expect("successful transaction");

        let report = conn
            .transact(
                &mut c,
                r#"[
            [:db/add "u" :foo/boolean true]
            [:db/add "p" :foo/boolean false]
        ]"#,
            )
            .expect("successful transaction");
        let yes = *report.tempids.get("u").expect("found it");

        let vv = Variable::from_valid_name("?v");

        let values = QueryInputs::with_value_sequence(vec![(vv, true.into())]);

        let read = conn.begin_read(&mut c).expect("read");

        // N.B., you might choose to algebrize _without_ validating that the
        // types are known. In this query we know that `?v` must be a boolean,
        // and so we can kinda generate our own required input types!
        let mut prepared = read
            .q_prepare(
                r#"[:find [?x ...]
                                              :in ?v
                                              :where [?x :foo/boolean ?v]]"#,
                values,
            )
            .expect("prepare succeeded");

        let yeses = prepared.run(None).expect("result");
        assert_eq!(
            yeses.results,
            QueryResults::Coll(vec![TypedValue::Ref(yes).into()])
        );

        let yeses_again = prepared.run(None).expect("result");
        assert_eq!(
            yeses_again.results,
            QueryResults::Coll(vec![TypedValue::Ref(yes).into()])
        );
    }

    #[test]
    fn test_compound_rollback() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();

        let tempid_offset = get_next_entid(&conn);

        // Nothing in the store => USER0 should be our starting point.
        assert_eq!(tempid_offset, USER0);

        let t = "[[:db/add \"one\" :db/ident :a/keyword1] \
                 [:db/add \"two\" :db/ident :a/keyword2]]";

        // Scoped borrow of `sqlite`.
        {
            let mut in_progress = conn
                .begin_transaction(&mut sqlite)
                .expect("begun successfully");
            let report = in_progress.transact(t).expect("transacted successfully");

            let one = *report.tempids.get("one").expect("found it");
            let two = *report.tempids.get("two").expect("found it");

            // The IDs are contiguous, starting at the previous part index.
            assert!(one != two);
            assert!(one == tempid_offset || one == tempid_offset + 1);
            assert!(two == tempid_offset || two == tempid_offset + 1);

            // Inside the InProgress we can see our changes.
            let during = in_progress
                .q_once("[:find ?x . :where [?x :db/ident :a/keyword1]]", None)
                .expect("query succeeded");

            assert_eq!(
                during.results,
                QueryResults::Scalar(Some(TypedValue::Ref(one).into()))
            );

            // And we can do direct lookup, too.
            let kw = in_progress
                .lookup_value_for_attribute(one, &edn::Keyword::namespaced("db", "ident"))
                .expect("lookup succeeded");
            assert_eq!(
                kw,
                Some(TypedValue::Keyword(
                    edn::Keyword::namespaced("a", "keyword1").into()
                ))
            );

            in_progress.rollback().expect("rollback succeeded");
        }

        let after = conn
            .q_once(
                &sqlite,
                "[:find ?x . :where [?x :db/ident :a/keyword1]]",
                None,
            )
            .expect("query succeeded");
        assert_eq!(after.results, QueryResults::Scalar(None));

        // The DB part table is unchanged.
        let tempid_offset_after = get_next_entid(&conn);
        assert_eq!(tempid_offset, tempid_offset_after);
    }

    #[test]
    fn test_transact_errors() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();

        // Good: empty transaction.
        let report = conn.transact(&mut sqlite, "[]").unwrap();
        assert_eq!(report.tx_id, 0x10000000 + 1);

        // Bad EDN: missing closing ']'.
        let report = conn.transact(&mut sqlite, "[[:db/add \"t\" :db/ident :a/keyword]");
        match report.expect_err("expected transact to fail for bad edn") {
            MentatError::EdnParseError(_) => {}
            x => panic!("expected EDN parse error, got {:?}", x),
        }

        // Good EDN.
        let report = conn
            .transact(&mut sqlite, "[[:db/add \"t\" :db/ident :a/keyword]]")
            .unwrap();
        assert_eq!(report.tx_id, 0x10000000 + 2);

        // Bad transaction data: missing leading :db/add.
        let report = conn.transact(&mut sqlite, "[[\"t\" :db/ident :b/keyword]]");
        match report.expect_err("expected transact error") {
            MentatError::EdnParseError(_) => {}
            x => panic!("expected EDN parse error, got {:?}", x),
        }

        // Good transaction data.
        let report = conn
            .transact(&mut sqlite, "[[:db/add \"u\" :db/ident :b/keyword]]")
            .unwrap();
        assert_eq!(report.tx_id, 0x10000000 + 3);

        // Bad transaction based on state of store: conflicting upsert.
        let report = conn.transact(
            &mut sqlite,
            "[[:db/add \"u\" :db/ident :a/keyword]
                                                  [:db/add \"u\" :db/ident :b/keyword]]",
        );
        match report.expect_err("expected transact error") {
            MentatError::DbError(e) => match e.kind() {
                ::db_traits::errors::DbErrorKind::SchemaConstraintViolation(_) => {}
                _ => panic!("expected SchemaConstraintViolation"),
            },
            x => panic!("expected db error, got {:?}", x),
        }
    }

    #[test]
    fn test_add_to_cache_failure_no_attribute() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();
        let _report = conn
            .transact(
                &mut sqlite,
                r#"[
            {  :db/ident       :foo/bar
               :db/valueType   :db.type/long },
            {  :db/ident       :foo/baz
               :db/valueType   :db.type/boolean }]"#,
            )
            .unwrap();

        let kw = kw!(:foo/bat);
        let schema = conn.current_schema();
        let res = conn.cache(
            &mut sqlite,
            &schema,
            &kw,
            CacheDirection::Forward,
            CacheAction::Register,
        );
        match res.expect_err("expected cache to fail") {
            MentatError::UnknownAttribute(msg) => assert_eq!(msg, ":foo/bat"),
            x => panic!("expected UnknownAttribute error, got {:?}", x),
        }
    }

    // TODO expand tests to cover lookup_value_for_attribute comparing with and without caching
    #[test]
    fn test_lookup_attribute_with_caching() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();
        let _report = conn
            .transact(
                &mut sqlite,
                r#"[
            {  :db/ident       :foo/bar
               :db/valueType   :db.type/long },
            {  :db/ident       :foo/baz
               :db/valueType   :db.type/boolean }]"#,
            )
            .expect("transaction expected to succeed");

        {
            let mut in_progress = conn.begin_transaction(&mut sqlite).expect("transaction");
            for _ in 1..100 {
                let _report = in_progress
                    .transact(
                        r#"[
            {  :foo/bar        100
               :foo/baz        false },
            {  :foo/bar        200
               :foo/baz        true },
            {  :foo/bar        100
               :foo/baz        false },
            {  :foo/bar        300
               :foo/baz        true },
            {  :foo/bar        400
               :foo/baz        false },
            {  :foo/bar        500
               :foo/baz        true }]"#,
                    )
                    .expect("transaction expected to succeed");
            }
            in_progress.commit().expect("Committed");
        }

        let entities = conn
            .q_once(&sqlite, r#"[:find ?e . :where [?e :foo/bar 400]]"#, None)
            .expect("Expected query to work")
            .into_scalar()
            .expect("expected rel results");
        let first = entities.expect("expected a result");
        let entid = match first {
            Binding::Scalar(TypedValue::Ref(entid)) => entid,
            x => panic!("expected Some(Ref), got {:?}", x),
        };

        let kw = kw!(:foo/bar);
        let start = Instant::now();
        let uncached_val = conn
            .lookup_value_for_attribute(&sqlite, entid, &kw)
            .expect("Expected value on lookup");
        let finish = Instant::now();
        let uncached_elapsed_time = finish.duration_since(start);
        println!("Uncached time: {:?}", uncached_elapsed_time);

        let schema = conn.current_schema();
        conn.cache(
            &mut sqlite,
            &schema,
            &kw,
            CacheDirection::Forward,
            CacheAction::Register,
        )
        .expect("expected caching to work");

        for _ in 1..5 {
            let start = Instant::now();
            let cached_val = conn
                .lookup_value_for_attribute(&sqlite, entid, &kw)
                .expect("Expected value on lookup");
            let finish = Instant::now();
            let cached_elapsed_time = finish.duration_since(start);
            assert_eq!(cached_val, uncached_val);

            println!("Cached time: {:?}", cached_elapsed_time);
            assert!(cached_elapsed_time < uncached_elapsed_time);
        }
    }

    #[test]
    fn test_cache_usage() {
        let mut sqlite = db::new_connection("").unwrap();
        let mut conn = Conn::connect(&mut sqlite).unwrap();

        let db_ident = (*conn.current_schema())
            .get_entid(&kw!(:db/ident))
            .expect("db_ident")
            .0;
        let db_type = (*conn.current_schema())
            .get_entid(&kw!(:db/valueType))
            .expect("db_ident")
            .0;
        println!("db/ident is {}", db_ident);
        println!("db/type is {}", db_type);
        let query = format!(
            "[:find ?ident . :where [?e {} :db/doc][?e {} ?type][?type {} ?ident]]",
            db_ident, db_type, db_ident
        );

        println!("Query is {}", query);

        assert!(!conn.current_cache().is_attribute_cached_forward(db_ident));

        {
            let mut ip = conn.begin_transaction(&mut sqlite).expect("began");

            let ident = ip
                .q_once(query.as_str(), None)
                .into_scalar_result()
                .expect("query");
            assert_eq!(
                ident,
                Some(TypedValue::typed_ns_keyword("db.type", "string").into())
            );

            let start = std::time::Instant::now();
            ip.q_once(query.as_str(), None)
                .into_scalar_result()
                .expect("query");
            let end = std::time::Instant::now();
            println!("Uncached took {}µs", (end - start).as_micros());

            ip.cache(
                &kw!(:db/ident),
                CacheDirection::Forward,
                CacheAction::Register,
            )
            .expect("registered");
            ip.cache(
                &kw!(:db/valueType),
                CacheDirection::Forward,
                CacheAction::Register,
            )
            .expect("registered");

            assert!(ip.cache.is_attribute_cached_forward(db_ident));

            let ident = ip
                .q_once(query.as_str(), None)
                .into_scalar_result()
                .expect("query");
            assert_eq!(
                ident,
                Some(TypedValue::typed_ns_keyword("db.type", "string").into())
            );

            let start = std::time::Instant::now();
            ip.q_once(query.as_str(), None)
                .into_scalar_result()
                .expect("query");
            let end = std::time::Instant::now();
            println!("Cached took {}µs", (end - start).as_micros());

            // If we roll back the change, our caching operations are also rolled back.
            ip.rollback().expect("rolled back");
        }

        assert!(!conn.current_cache().is_attribute_cached_forward(db_ident));

        {
            let mut ip = conn.begin_transaction(&mut sqlite).expect("began");

            let ident = ip
                .q_once(query.as_str(), None)
                .into_scalar_result()
                .expect("query");
            assert_eq!(
                ident,
                Some(TypedValue::typed_ns_keyword("db.type", "string").into())
            );
            ip.cache(
                &kw!(:db/ident),
                CacheDirection::Forward,
                CacheAction::Register,
            )
            .expect("registered");
            ip.cache(
                &kw!(:db/valueType),
                CacheDirection::Forward,
                CacheAction::Register,
            )
            .expect("registered");

            assert!(ip.cache.is_attribute_cached_forward(db_ident));

            ip.commit().expect("rolled back");
        }

        assert!(conn.current_cache().is_attribute_cached_forward(db_ident));
        assert!(conn.current_cache().is_attribute_cached_forward(db_type));
    }
}