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Wiki / Plan Nodes / Scan

Tid Scan

TidScan

Fetches table tuples using tuple identifiers.

Reading PostgreSQL 18.6.

Description

Fetches table tuples using tuple identifiers.

Core node tag
T_TidScan
Structured EXPLAIN Node Type
Tid Scan
Inputs
A relation and tuple identifiers
Output
Selected table tuples
Executor initializer
ExecInitTidScan
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: Tid Scan.

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

nodeTidscan.c Routines to support direct tid scans of relations

ExecTidScan scans a relation using tids ExecInitTidScan creates and initializes state info. ExecReScanTidScan rescans the tid relation. ExecEndTidScan releases all storage.

It's sufficient to check varattno to identify the CTID variable, as any Var in the relation scan qual must be for our table. (Even if it's a parameterized scan referencing some other table's CTID, the other table's Var would have become a Param by the time it gets here.)

Extract the qual subexpressions that yield TIDs to search for, and compile them into ExprStates if they're ordinary expressions.

CURRENT OF is a special case that we can't compile usefully; just drop it into the TidExpr list as-is.

EXPLAIN identity in core source

case T_TidScan:
			pname = sname = "Tid Scan";
			break;

EXPLAIN labels in this source build

Text-format labelStructured node identity
Tid ScanTid Scan

Related entries

Documentation and source

Source build
Version
18.6
Build
PostgreSQL 18.6 source archive
Source fingerprint
555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f

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

Export JSON · Back to Plan Nodes · Recorded in PostgreSQL 10 through 20; the first sample is not necessarily its introduction.