| name | 0.1.6-understand-row_level_locking |
| description | [0.1.6] Lock management at the individual row granularity via row_lock entries in lock_manager's lock table; enables h |
understand-row_level_locking
CALL NUMBER: database_transaction_isolation_and_concurrency_c.row_level_locking : deep_database_transaction(6), deep_isolation_level(1)
DEFINITION: Lock management at the individual row granularity via row_lock entries in lock_manager's lock table; enables high concurrency but increases lock_manager overhead.
Invoke this skill to understand row_level_locking down to its primitives. The RELATIVE ROOT below is the least-fixed-point closure of everything it bundles from — the full import cone, grouped by the lib each prim comes from. Projected from a prover-typed KB (MAP/SWI-Prolog consistency gate): every reference below resolves.
THE RELATIVE ROOT (the import cone, by lib)
from database_transaction_isolation_and_concurrency_c
- atomicity (d2): The all-or-nothing property: a transaction's effects are either fully applied or fully absent; implemented via undo_log and transaction rollback.
- commit (d3): The act of making a transaction's effects permanent: flush log records to durable storage, release locks, transition transaction_state to committed.
- rollback (d3): The act of undoing a transaction's effects using undo_log entries, returning the database to its pre-transaction state.
- transaction_log (d3): An append-only sequence of records tracking every change made by transactions; the primary mechanism for atomicity and durability.
- transaction_state (d3): The current phase of a transaction lifecycle: active, partially_committed, committed, aborted; drives lock release and recovery behavior.
- undo_log (d3): Log records describing the previous state of modified data; used to undo uncommitted transaction changes during rollback and recovery.
- write_ahead_logging (d3): A protocol requiring log records be flushed to durable storage before the corresponding data changes are applied; ensures durability and atomicity.
- aborted_state (d4): The terminal transaction_state after rollback completes; all acquired locks are released and the transaction cannot be restarted automatically.
- committed (d4): The terminal transaction_state after durable persistence of all changes; locks are released per locking_protocol rules.
from deep_database_transaction
- statement (d1): A single SQL operation within a transaction; atomicity requires that each statement either fully completes its effect or fully reverts before the next statement begins.
- all_or_nothing (d3): The conceptual guarantee that a transaction executes as an indivisible unit: either every operation succeeds or no operation has any effect.
- partial_state_prevention (d4): The enforcement mechanism ensuring that if a transaction fails at any point before transaction_boundary, no tuple modifications leak into committed_data; achieved by deferring all visible effects until commit.
- before_image (d4): The committed database state of a row immediately before a transaction modifies it; recorded in the undo_log so the modification can be undone if the transaction rolls back.
- compensation_action (d4): A corrective operation executed when forward undo via undo_log is impossible; used in distributed systems where original transaction steps cannot be directly reversed, preserving atomicity through logically equivalent alternatives.
- transaction_boundary (d5): The demarcation point between consecutive transaction executions defining the scope over which atomicity applies; all effects within are committed or none are, with no partial visibility across the boundary.
from deep_isolation_level
- committed_data (d5): database state resulting from successfully completed transactions; constitutes the visible universe for read_committed queries
CONSUMERS (what needs this)
lock_timeout_handling, non_repeatable_read_possible, phantom_read_possible, read_lock_release, write_lock_held_until_commit
Projected from the database transaction isolation and concurrency control KB (217 concepts / 124 relations) — consistency-typed by MAP; the facet list after the colon IS the cross-lib dependency web.
(leaf — this is an actual skill.)
