Method exists_in_txn

nodedb/src/engine/sparse/btree.rs:167–184

Check whether a document exists within an externally-owned write transaction — the probe used by INSERT-with-unique-PK semantics. Uses the caller's write txn so the check is linearizable with the subsequent `put_in_txn`: no other writer can slip a row in between the "does it exist" read and the insert commit. Returns `Ok(true)` if a document with this (tenant, collection, document_id) is already

(
        &self,
        txn: &WriteTransaction,
        tenant_id: u64,
        collection: &str,
        document_id: &str,
    )

    /// if a document with this (tenant, collection, document_id) is
    /// already present.
    pub fn exists_in_txn(
        &self,
        txn: &WriteTransaction,
        tenant_id: u64,
        collection: &str,
        document_id: &str,
    ) -> crate::Result<bool> {
        with_tenant_key(tenant_id, collection, document_id, |key| {
            let table = txn
                .open_table(DOCUMENTS)
                .map_err(|e| redb_err("open table", e))?;
            match table.get(key) {
                Ok(Some(_)) => Ok(true),
                Ok(None) => Ok(false),
                Err(e) => Err(redb_err("exists_in_txn", e)),
            }
        })
    }

    /// Batch insert or update multiple documents in a single redb transaction.
    pub fn batch_put(