From de729da30d73d6a120bf08f7820014df49989bb0 Mon Sep 17 00:00:00 2001
From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Thu, 16 Jan 2025 15:35:03 -0800
Subject: [PATCH v9 1/6] Introduces table AM APIs for parallel table vacuuming.

This commit introduces the following new table AM APIs for parallel
heap vacuuming:

- parallel_vacuum_compute_workers
- parallel_vacuum_estimate
- parallel_vacuum_initialize
- parallel_vacuum_initialize_worker
- parallel_vacuum_remove_dead_items

There is no code using these new APIs for now. Upcoming parallel
vacuum patches utilize these APIs.

Reviewed-by:
Discussion: https://postgr.es/m/
---
 src/include/access/tableam.h | 114 +++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)

diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index 131c050c15f..6eb01c7766d 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -35,6 +35,9 @@ extern PGDLLIMPORT bool synchronize_seqscans;
 
 struct BulkInsertStateData;
 struct IndexInfo;
+struct ParallelVacuumState;
+struct ParallelContext;
+struct ParallelWorkerContext;
 struct SampleScanState;
 struct VacuumParams;
 struct ValidateIndexState;
@@ -655,6 +658,60 @@ typedef struct TableAmRoutine
 									struct VacuumParams *params,
 									BufferAccessStrategy bstrategy);
 
+	/* ------------------------------------------------------------------------
+	 * Callbacks for parallel table vacuum.
+	 * ------------------------------------------------------------------------
+	 */
+
+	/*
+	 * Compute the number of parallel workers for parallel table vacuum. The
+	 * function must return 0 to disable parallel table vacuum.
+	 */
+	int			(*parallel_vacuum_compute_workers) (Relation rel);
+
+	/*
+	 * Estimate the size of shared memory that the parallel table vacuum needs
+	 * for AM
+	 *
+	 * Not called if parallel table vacuum is disabled.
+	 */
+	void		(*parallel_vacuum_estimate) (Relation rel,
+											 struct ParallelContext *pcxt,
+											 int nworkers,
+											 void *state);
+
+	/*
+	 * Initialize DSM space for parallel table vacuum.
+	 *
+	 * Not called if parallel table vacuum is disabled.
+	 */
+	void		(*parallel_vacuum_initialize) (Relation rel,
+											   struct ParallelContext *pctx,
+											   int nworkers,
+											   void *state);
+
+	/*
+	 * Initialize AM-specific vacuum state for worker processes.
+	 *
+	 * The state_out is the output parameter so that an arbitrary data can be
+	 * passed to the subsequent callback, parallel_vacuum_remove_dead_items.
+	 *
+	 * Not called if parallel table vacuum is disabled.
+	 */
+	void		(*parallel_vacuum_initialize_worker) (Relation rel,
+													  struct ParallelVacuumState *pvs,
+													  struct ParallelWorkerContext *pwcxt,
+													  void **state_out);
+
+	/*
+	 * Execute a parallel scan to remove the dead items.
+	 *
+	 * Not called if parallel table vacuum is disabled.
+	 */
+	void		(*parallel_vacuum_remove_dead_items) (Relation rel,
+													  struct ParallelVacuumState *pvs,
+													  void *state);
+
 	/*
 	 * Prepare to analyze block `blockno` of `scan`. The scan has been started
 	 * with table_beginscan_analyze().  See also
@@ -1716,6 +1773,63 @@ table_relation_vacuum(Relation rel, struct VacuumParams *params,
 	rel->rd_tableam->relation_vacuum(rel, params, bstrategy);
 }
 
+/* ----------------------------------------------------------------------------
+ * Parallel vacuum related functions.
+ * ----------------------------------------------------------------------------
+ */
+
+/*
+ * Return the number of parallel workers for a parallel vacuum scan of this
+ * relation.
+ */
+static inline int
+table_parallel_vacuum_compute_workers(Relation rel)
+{
+	return rel->rd_tableam->parallel_vacuum_compute_workers(rel);
+}
+
+/*
+ * Estimate the size of shared memory needed for a parallel vacuum scan of this
+ * of this relation.
+ */
+static inline void
+table_parallel_vacuum_estimate(Relation rel, struct ParallelContext *pcxt,
+							   int nworkers, void *state)
+{
+	rel->rd_tableam->parallel_vacuum_estimate(rel, pcxt, nworkers, state);
+}
+
+/*
+ * Initialize shared memory area for a parallel vacuum scan of this relation.
+ */
+static inline void
+table_parallel_vacuum_initialize(Relation rel, struct ParallelContext *pcxt,
+								 int nworkers, void *state)
+{
+	rel->rd_tableam->parallel_vacuum_initialize(rel, pcxt, nworkers, state);
+}
+
+/*
+ * Initialize AM-specific vacuum state for worker processes.
+ */
+static inline void
+table_parallel_vacuum_initialize_worker(Relation rel, struct ParallelVacuumState *pvs,
+										struct ParallelWorkerContext *pwcxt,
+										void **state_out)
+{
+	rel->rd_tableam->parallel_vacuum_initialize_worker(rel, pvs, pwcxt, state_out);
+}
+
+/*
+ * Perform a parallel vacuums scan to remove the collected dead items.
+ */
+static inline void
+table_parallel_vacuum_remove_dead_items(Relation rel, struct ParallelVacuumState *pvs,
+										void *state)
+{
+	rel->rd_tableam->parallel_vacuum_remove_dead_items(rel, pvs, state);
+}
+
 /*
  * Prepare to analyze the next block in the read stream. The scan needs to
  * have been  started with table_beginscan_analyze().  Note that this routine
-- 
2.43.5