Struct ConcurrentTx 

pub struct ConcurrentTx {
    pub handle: TxHandle,
    pub tables: HashMap<String, Table>,
    pub tables_at_begin: HashMap<String, Table>,
    pub schema_at_begin: Vec<String>,
}

Per-Connection snapshot of BEGIN CONCURRENT state.

Lives on Connection, not on Database — multiple sibling connections each carry their own concurrent transaction without stepping on each other’s snapshots.

Fields

handle: TxHandle

RAII handle into the ActiveTxRegistry. Drops when this struct drops (commit, rollback, or Connection close), at which point the transaction is unregistered.

tables: HashMap<String, Table>

Working snapshot of Database::tables taken at BEGIN CONCURRENT via Table::deep_clone. Each statement’s executor pass transparently swaps this in for db.tables so writes land here, not on the live database.

tables_at_begin: HashMap<String, Table>

Immutable second clone of Database::tables taken at BEGIN. Diffing tables against this at commit produces the write-set. We can’t diff against the live Database::tables directly because between our BEGIN and our COMMIT, other concurrent transactions may have committed — their writes show up as differences against the live state but aren’t ours, and treating them as our DELETEs would silently undo someone else’s commit. The doubled memory cost (two full clones per transaction) is the price for that correctness in v0; the obvious follow-up is a per-touched-row begin-state map that captures only the rows we actually read or wrote.

schema_at_begin: Vec<String>

Sorted table-name fingerprint of Database::tables at BEGIN. Used at commit to detect that DDL ran on the live database under us — v0 rejects DDL inside the tx, but nothing prevents another connection from running it outside.

Implementations

impl ConcurrentTx

pub fn begin( clock: &MvccClock, registry: &ActiveTxRegistry, live_tables: &HashMap<String, Table>, ) -> Self

Allocates a new transaction. Advances the clock by one (the TxHandle::begin_ts), records the table-name fingerprint, and deep-clones every table.

Caller is expected to have already verified journal_mode == Mvcc and that no transaction is open.

pub fn begin_ts(&self) -> u64

Convenience — the begin_ts snapshot timestamp this transaction took at BEGIN. Used at commit to validate against MvStore versions that committed after this snapshot.

pub fn schema_unchanged(&self, live_tables: &HashMap<String, Table>) -> bool

True if live_tables has the same table-name set this transaction recorded at BEGIN. Used at commit to surface a typed error rather than silently committing onto a schema that drifted under us.

Trait Implementations

impl Debug for ConcurrentTx

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.