LockRows

Description

Locks rows selected by its child for row-locking clauses.

Core node tag

T_LockRows

Structured EXPLAIN Node Type

LockRows

Inputs

One child plan with row identity information

Output

Locked qualifying tuples

Executor initializer

ExecInitLockRows

Memory mechanism

unclassified

EXPLAIN names and attributes

Structured formats use the Node Type above. Text-format spellings can also include operation, strategy, join type, scan direction or aggregation-stage attributes.

Text names recorded by this source: LockRows.

Parallel-aware and parallel-safe are different plan properties. A node running inside a parallel worker is not necessarily a parallel-aware node.

Memory and temporary storage

This extraction does not assign a universal memory limit or spill policy to this node. Inspect the same-build implementation and its expressions or provider.

Parallel execution and instrumentation

The source callbacks below can coordinate execution or collect worker instrumentation. Their presence is not a blanket claim that this node supports a shared parallel scan or shared state.

Callbacks in this build: none extracted from this node implementation.

Executor implementation notes

nodeLockRows.c Routines to handle FOR UPDATE/FOR SHARE row locking

We don't need EvalPlanQual unless we get updated tuple version(s)

Attempt to lock the source tuple(s). (Note we only have locking rowmarks in lr_arowMarks.)

if FDW says tuple was updated before getting locked, we need to perform EPQ testing to see if quals are still satisfied

The target tuple was already updated or deleted by the current command, or by a later command in the current transaction. We *must* ignore the tuple in the former case, so as to avoid the "Halloween problem" of repeated update attempts. In the latter case it might be sensible to fetch the updated tuple instead, but doing so would require changing heap_update and heap_delete to not complain about updating "invisible" tuples, which seems pretty scary (table_tuple_lock will not complain, but few callers expect TM_Invisible, and we're not one of them). So for now, treat the tuple as deleted and do not process.

EXPLAIN identity in core source

case T_LockRows:
			pname = sname = "LockRows";
			break;

Related entries

• EXPLAIN
• Using EXPLAIN
• Parallel plans
• Row locks

Documentation and source

• src/backend/commands/explain.c:1598
• src/backend/executor/execProcnode.c:375
• src/backend/executor/nodeLockRows.c
• src/include/nodes/plannodes.h

Compare versions

PostgreSQL 17 → 18: unchanged.

Compares recorded interfaces and attributes. Source fingerprints and build metadata are excluded; an absent sample is not proof of the introduction or removal release.

Related entries

• LimitLimit
• ProjectSetProjectSet
• ResultResult