moving LastWrittenLSNCache to Neon Extension (#11031)

## Problem

We currently have this code duplicated across different PG versions.
Moving this to an extension would reduce duplication and simplify
maintenance.

## Summary of changes

Moving the LastWrittenLSN code from PG versions to the Neon extension
and linking it with hooks.

Related Postgres PR: https://github.com/neondatabase/postgres/pull/590

Closes: https://github.com/neondatabase/neon/issues/10973

---------

Co-authored-by: Tristan Partin <tristan@neon.tech>

compute/patches/pgvector.patch

@@ -15,7 +15,7 @@ index 7a4b88c..56678af 100644
  HEADERS = src/halfvec.h src/sparsevec.h src/vector.h
  
 diff --git a/src/hnswbuild.c b/src/hnswbuild.c
-index b667478..fc1897c 100644
+index b667478..dc95d89 100644
 --- a/src/hnswbuild.c
 +++ b/src/hnswbuild.c
 @@ -843,9 +843,17 @@ HnswParallelBuildMain(dsm_segment *seg, shm_toc *toc)
@@ -36,7 +36,7 @@ index b667478..fc1897c 100644
  	/* Close relations within worker */
  	index_close(indexRel, indexLockmode);
  	table_close(heapRel, heapLockmode);
-@@ -1100,12 +1108,38 @@ BuildIndex(Relation heap, Relation index, IndexInfo *indexInfo,
+@@ -1100,12 +1108,39 @@ BuildIndex(Relation heap, Relation index, IndexInfo *indexInfo,
  	SeedRandom(42);
  #endif
  
@@ -62,10 +62,11 @@ index b667478..fc1897c 100644
 +#else
 +			RelFileNode rlocator = RelationGetSmgr(index)->smgr_rnode.node;
 +#endif
-+
-+			SetLastWrittenLSNForBlockRange(XactLastRecEnd, rlocator,
-+									   MAIN_FORKNUM, 0, RelationGetNumberOfBlocks(index));
-+			SetLastWrittenLSNForRelation(XactLastRecEnd, rlocator, MAIN_FORKNUM);
++			if (set_lwlsn_block_range_hook)
++				set_lwlsn_block_range_hook(XactLastRecEnd, rlocator,
++										   MAIN_FORKNUM, 0, RelationGetNumberOfBlocks(index));
++			if (set_lwlsn_relation_hook)
++				set_lwlsn_relation_hook(XactLastRecEnd, rlocator, MAIN_FORKNUM);
 +		}
 +#endif
 +	}

compute/patches/rum.patch

@@ -1,11 +1,5 @@
-commit 68f3b3b0d594f08aacc4a082ee210749ed5677eb
-Author: Anastasia Lubennikova <anastasia@neon.tech>
-Date:   Mon Jul 15 12:31:56 2024 +0100
-
-    Neon: fix unlogged index build patch
-
 diff --git a/src/ruminsert.c b/src/ruminsert.c
-index e8b209d..e89bf2a 100644
+index 255e616..7a2240f 100644
 --- a/src/ruminsert.c
 +++ b/src/ruminsert.c
 @@ -628,6 +628,10 @@ rumbuild(Relation heap, Relation index, struct IndexInfo *indexInfo)
@@ -30,7 +24,7 @@ index e8b209d..e89bf2a 100644
  	/*
  	 * Write index to xlog
  	 */
-@@ -713,6 +721,21 @@ rumbuild(Relation heap, Relation index, struct IndexInfo *indexInfo)
+@@ -713,6 +721,22 @@ rumbuild(Relation heap, Relation index, struct IndexInfo *indexInfo)
  		UnlockReleaseBuffer(buffer);
  	}
  
@@ -41,9 +35,10 @@ index e8b209d..e89bf2a 100644
 +#else
 +		RelFileNode rlocator = RelationGetSmgr(index)->smgr_rnode.node;
 +#endif
-+
-+		SetLastWrittenLSNForBlockRange(XactLastRecEnd, rlocator, MAIN_FORKNUM, 0, RelationGetNumberOfBlocks(index));
-+		SetLastWrittenLSNForRelation(XactLastRecEnd, rlocator, MAIN_FORKNUM);
++		if (set_lwlsn_block_range_hook)
++			set_lwlsn_block_range_hook(XactLastRecEnd, rlocator, MAIN_FORKNUM, 0, RelationGetNumberOfBlocks(index));
++		if (set_lwlsn_relation_hook)
++			set_lwlsn_relation_hook(XactLastRecEnd, rlocator, MAIN_FORKNUM);
 +
 +		smgr_end_unlogged_build(index->rd_smgr);
 +	}

pgxn/neon/Makefile

@@ -10,6 +10,7 @@ OBJS = \
 	libpagestore.o \
 	logical_replication_monitor.o \
 	neon.o \
+	neon_lwlsncache.o \
 	neon_pgversioncompat.o \
 	neon_perf_counters.o \
 	neon_utils.o \

pgxn/neon/file_cache.c

@@ -48,6 +48,7 @@
 #include "hll.h"
 #include "bitmap.h"
 #include "neon.h"
+#include "neon_lwlsncache.h"
 #include "neon_perf_counters.h"
 
 #define CriticalAssert(cond) do if (!(cond)) elog(PANIC, "LFC: assertion %s failed at %s:%d: ", #cond, __FILE__, __LINE__); while (0)
@@ -999,7 +1000,9 @@ lfc_prefetch(NRelFileInfo rinfo, ForkNumber forknum, BlockNumber blkno,
 		LWLockRelease(lfc_lock);
 		return false;
 	}
-	lwlsn = GetLastWrittenLSN(rinfo, forknum, blkno);
+	
+	lwlsn = neon_get_lwlsn(rinfo, forknum, blkno);
+
 	if (lwlsn > lsn)
 	{
 		elog(DEBUG1, "Skip LFC write for %d because LwLSN=%X/%X is greater than not_nodified_since LSN %X/%X",

pgxn/neon/neon.c

@@ -33,6 +33,7 @@
 
 #include "extension_server.h"
 #include "neon.h"
+#include "neon_lwlsncache.h"
 #include "control_plane_connector.h"
 #include "logical_replication_monitor.h"
 #include "unstable_extensions.h"
@@ -437,6 +438,8 @@ _PG_init(void)
 
 	pg_init_libpagestore();
 	pg_init_walproposer();
+	init_lwlsncache();
+
 	pagestore_smgr_init();
 	Custom_XLogReaderRoutines = NeonOnDemandXLogReaderRoutines;
 

pgxn/neon/neon_lwlsncache.c

@@ -0,0 +1,508 @@
+#include "postgres.h"
+
+#include "neon_lwlsncache.h"
+
+#include "miscadmin.h"
+#include "access/xlog.h"
+#include "storage/ipc.h"
+#include "storage/shmem.h"
+#include "storage/buf_internals.h"
+#include "utils/guc.h"
+#include "utils/hsearch.h"
+
+
+
+typedef struct LastWrittenLsnCacheEntry
+{
+	BufferTag	key;
+	XLogRecPtr	lsn;
+	/* double linked list for LRU replacement algorithm */
+	dlist_node	lru_node;
+} LastWrittenLsnCacheEntry;
+
+typedef struct LwLsnCacheCtl {
+	int lastWrittenLsnCacheSize;
+	/*
+	* Maximal last written LSN for pages not present in lastWrittenLsnCache
+	*/
+	XLogRecPtr  maxLastWrittenLsn;
+
+	/*
+	* Double linked list to implement LRU replacement policy for last written LSN cache.
+	* Access to this list as well as to last written LSN cache is protected by 'LastWrittenLsnLock'.
+	*/
+	dlist_head lastWrittenLsnLRU;
+} LwLsnCacheCtl;
+
+
+/*
+ * Cache of last written LSN for each relation page.
+ * Also to provide request LSN for smgrnblocks, smgrexists there is pseudokey=InvalidBlockId which stores LSN of last
+ * relation metadata update.
+ * Size of the cache is limited by GUC variable lastWrittenLsnCacheSize ("lsn_cache_size"),
+ * pages are replaced using LRU algorithm, based on L2-list.
+ * Access to this cache is protected by 'LastWrittenLsnLock'.
+ */
+static HTAB *lastWrittenLsnCache;
+
+LwLsnCacheCtl* LwLsnCache;
+
+static int lwlsn_cache_size = (128 * 1024); 
+
+
+static void
+lwlc_register_gucs(void)
+{
+	DefineCustomIntVariable("neon.last_written_lsn_cache_size",
+							"Size of last written LSN cache used by Neon",
+							NULL,
+							&lwlsn_cache_size,
+							(128*1024), 1024, INT_MAX,
+							PGC_POSTMASTER,
+							0, /* plain units */
+							NULL, NULL, NULL);
+}
+
+static XLogRecPtr SetLastWrittenLSNForBlockRangeInternal(XLogRecPtr lsn,
+														 NRelFileInfo rlocator,
+														 ForkNumber forknum,
+														 BlockNumber from,
+														 BlockNumber n_blocks);
+
+/* All the necessary hooks are defined here */
+
+
+/* These hold the set_lwlsn_* hooks which were installed before ours, if any */
+static set_lwlsn_block_range_hook_type prev_set_lwlsn_block_range_hook = NULL;
+static set_lwlsn_block_v_hook_type prev_set_lwlsn_block_v_hook = NULL;
+static set_lwlsn_block_hook_type prev_set_lwlsn_block_hook = NULL;
+static set_max_lwlsn_hook_type prev_set_max_lwlsn_hook = NULL;
+static set_lwlsn_relation_hook_type prev_set_lwlsn_relation_hook = NULL;
+static set_lwlsn_db_hook_type prev_set_lwlsn_db_hook = NULL;
+
+static shmem_startup_hook_type prev_shmem_startup_hook;
+
+#if PG_VERSION_NUM >= 150000
+static shmem_request_hook_type prev_shmem_request_hook;
+#endif
+
+static void shmemrequest(void);
+static void shmeminit(void);
+static void neon_set_max_lwlsn(XLogRecPtr lsn);
+
+void
+init_lwlsncache(void)
+{
+	if (!process_shared_preload_libraries_in_progress)
+		ereport(ERROR, errcode(ERRCODE_INTERNAL_ERROR), errmsg("Loading of shared preload libraries is not in progress. Exiting"));
+	
+	lwlc_register_gucs();
+
+	prev_shmem_startup_hook = shmem_startup_hook;
+	shmem_startup_hook = shmeminit;
+
+	#if PG_VERSION_NUM >= 150000
+	prev_shmem_request_hook = shmem_request_hook;
+	shmem_request_hook = shmemrequest;
+	#else
+	shmemrequest();
+	#endif
+	
+	prev_set_lwlsn_block_range_hook = set_lwlsn_block_range_hook;
+	set_lwlsn_block_range_hook = neon_set_lwlsn_block_range;
+	prev_set_lwlsn_block_v_hook = set_lwlsn_block_v_hook;
+	set_lwlsn_block_v_hook = neon_set_lwlsn_block_v;
+	prev_set_lwlsn_block_hook = set_lwlsn_block_hook;
+	set_lwlsn_block_hook = neon_set_lwlsn_block;
+	prev_set_max_lwlsn_hook = set_max_lwlsn_hook;
+	set_max_lwlsn_hook = neon_set_max_lwlsn;
+	prev_set_lwlsn_relation_hook = set_lwlsn_relation_hook;
+	set_lwlsn_relation_hook = neon_set_lwlsn_relation;
+	prev_set_lwlsn_db_hook = set_lwlsn_db_hook;
+	set_lwlsn_db_hook = neon_set_lwlsn_db;
+}
+
+
+static void shmemrequest(void) {
+	Size requested_size = sizeof(LwLsnCacheCtl);
+	
+	requested_size += hash_estimate_size(lwlsn_cache_size, sizeof(LastWrittenLsnCacheEntry));
+
+	RequestAddinShmemSpace(requested_size);
+
+	#if PG_VERSION_NUM >= 150000
+	if (prev_shmem_request_hook)
+			prev_shmem_request_hook();
+	#endif
+}
+
+static void shmeminit(void) {
+	static HASHCTL info;
+	bool found;
+	if (lwlsn_cache_size > 0)
+	{
+		info.keysize = sizeof(BufferTag);
+		info.entrysize = sizeof(LastWrittenLsnCacheEntry);
+		lastWrittenLsnCache = ShmemInitHash("last_written_lsn_cache",
+			lwlsn_cache_size, lwlsn_cache_size,
+										&info,
+										HASH_ELEM | HASH_BLOBS);
+		LwLsnCache = ShmemInitStruct("neon/LwLsnCacheCtl", sizeof(LwLsnCacheCtl), &found);
+		// Now set the size in the struct
+		LwLsnCache->lastWrittenLsnCacheSize = lwlsn_cache_size;
+		if (found) {
+			return;
+		}
+	}
+	dlist_init(&LwLsnCache->lastWrittenLsnLRU);
+    LwLsnCache->maxLastWrittenLsn = GetRedoRecPtr();
+	if (prev_shmem_startup_hook) {
+		prev_shmem_startup_hook();
+	}
+}
+
+/*
+ * neon_get_lwlsn -- Returns maximal LSN of written page.
+ * It returns an upper bound for the last written LSN of a given page,
+ * either from a cached last written LSN or a global maximum last written LSN.
+ * If rnode is InvalidOid then we calculate maximum among all cached LSN and maxLastWrittenLsn.
+ * If cache is large enough, iterating through all hash items may be rather expensive.
+ * But neon_get_lwlsn(InvalidOid) is used only by neon_dbsize which is not performance critical.
+ */
+XLogRecPtr
+neon_get_lwlsn(NRelFileInfo rlocator, ForkNumber forknum, BlockNumber blkno)
+{
+	XLogRecPtr lsn;
+	LastWrittenLsnCacheEntry* entry;
+
+	Assert(LwLsnCache->lastWrittenLsnCacheSize != 0);
+
+	LWLockAcquire(LastWrittenLsnLock, LW_SHARED);
+
+	/* Maximal last written LSN among all non-cached pages */
+	lsn = LwLsnCache->maxLastWrittenLsn;
+
+	if (NInfoGetRelNumber(rlocator) != InvalidOid)
+	{
+		BufferTag key;
+		Oid spcOid = NInfoGetSpcOid(rlocator);
+		Oid dbOid = NInfoGetDbOid(rlocator);
+		Oid relNumber = NInfoGetRelNumber(rlocator);
+		BufTagInit(key,  relNumber, forknum, blkno, spcOid, dbOid);
+		
+		entry = hash_search(lastWrittenLsnCache, &key, HASH_FIND, NULL);
+		if (entry != NULL)
+			lsn = entry->lsn;
+		else
+		{
+			LWLockRelease(LastWrittenLsnLock);
+			LWLockAcquire(LastWrittenLsnLock, LW_EXCLUSIVE);
+			/*
+			 * In case of statements CREATE TABLE AS SELECT... or INSERT FROM SELECT... we are fetching data from source table
+			 * and storing it in destination table. It cause problems with prefetch last-written-lsn is known for the pages of
+			 * source table (which for example happens after compute restart). In this case we get get global value of
+			 * last-written-lsn which is changed frequently as far as we are writing pages of destination table.
+			 * As a result request-lsn for the prefetch and request-let when this page is actually needed are different
+			 * and we got exported prefetch request. So it actually disarms prefetch.
+			 * To prevent that, we re-insert the page with the latest LSN, so that it's
+			 * less likely the LSN for this page will get evicted from the LwLsnCache
+			 * before the page is read.
+			 */
+			 lsn = SetLastWrittenLSNForBlockRangeInternal(lsn, rlocator, forknum, blkno, 1);
+		}
+	}
+	else
+	{
+		HASH_SEQ_STATUS seq;
+		/* Find maximum of all cached LSNs */
+		hash_seq_init(&seq, lastWrittenLsnCache);
+		while ((entry = (LastWrittenLsnCacheEntry *) hash_seq_search(&seq)) != NULL)
+		{
+			if (entry->lsn > lsn)
+				lsn = entry->lsn;
+		}
+	}
+	LWLockRelease(LastWrittenLsnLock);
+
+	return lsn;
+}
+
+static void neon_set_max_lwlsn(XLogRecPtr lsn) {
+	LWLockAcquire(LastWrittenLsnLock, LW_EXCLUSIVE);
+	LwLsnCache->maxLastWrittenLsn = lsn;
+	LWLockRelease(LastWrittenLsnLock);
+}
+
+/*
+ * GetLastWrittenLSN -- Returns maximal LSN of written page.
+ * It returns an upper bound for the last written LSN of a given page,
+ * either from a cached last written LSN or a global maximum last written LSN.
+ * If rnode is InvalidOid then we calculate maximum among all cached LSN and maxLastWrittenLsn.
+ * If cache is large enough, iterating through all hash items may be rather expensive.
+ * But GetLastWrittenLSN(InvalidOid) is used only by neon_dbsize which is not performance critical.
+ */
+void
+neon_get_lwlsn_v(NRelFileInfo relfilenode, ForkNumber forknum,
+				   BlockNumber blkno, int nblocks, XLogRecPtr *lsns)
+{
+	LastWrittenLsnCacheEntry* entry;
+	XLogRecPtr lsn;
+
+	Assert(LwLsnCache->lastWrittenLsnCacheSize != 0);
+	Assert(nblocks > 0);
+	Assert(PointerIsValid(lsns));
+
+	LWLockAcquire(LastWrittenLsnLock, LW_SHARED);
+
+	if (NInfoGetRelNumber(relfilenode) != InvalidOid)
+	{
+		BufferTag key;
+		bool missed_keys = false;
+		Oid spcOid = NInfoGetSpcOid(relfilenode);
+		Oid dbOid = NInfoGetDbOid(relfilenode);
+		Oid relNumber = NInfoGetRelNumber(relfilenode);
+		BufTagInit(key,  relNumber, forknum, blkno, spcOid, dbOid);
+
+		for (int i = 0; i < nblocks; i++)
+		{
+			/* Maximal last written LSN among all non-cached pages */
+			key.blockNum = blkno + i;
+
+			entry = hash_search(lastWrittenLsnCache, &key, HASH_FIND, NULL);
+			if (entry != NULL)
+			{
+ 				lsns[i] = entry->lsn;
+			}
+			else
+			{
+				/* Mark this block's LSN as missing - we'll update the LwLSN for missing blocks in bulk later */
+				lsns[i] = InvalidXLogRecPtr;
+				missed_keys = true;
+			}
+		}
+
+		/*
+		 * If we had any missing LwLSN entries, we add the missing ones now.
+		 * By doing the insertions in one batch, we decrease lock contention.
+		 */
+		if (missed_keys)
+		{
+			LWLockRelease(LastWrittenLsnLock);
+			LWLockAcquire(LastWrittenLsnLock, LW_EXCLUSIVE);
+
+			lsn = LwLsnCache->maxLastWrittenLsn;
+
+			for (int i = 0; i < nblocks; i++)
+			{
+				if (lsns[i] == InvalidXLogRecPtr)
+				{
+					lsns[i] = lsn;
+					SetLastWrittenLSNForBlockRangeInternal(lsn, relfilenode, forknum, blkno + i, 1);
+				}
+			}
+		}
+	}
+	else
+	{
+		HASH_SEQ_STATUS seq;
+		lsn = LwLsnCache->maxLastWrittenLsn;
+		/* Find maximum of all cached LSNs */
+		hash_seq_init(&seq, lastWrittenLsnCache);
+		while ((entry = (LastWrittenLsnCacheEntry *) hash_seq_search(&seq)) != NULL)
+		{
+			if (entry->lsn > lsn)
+				lsn = entry->lsn;
+		}
+
+		for (int i = 0; i < nblocks; i++)
+			lsns[i] = lsn;
+	}
+	LWLockRelease(LastWrittenLsnLock);
+}
+
+/*
+ * Guts for SetLastWrittenLSNForBlockRange.
+ * Caller must ensure LastWrittenLsnLock is held in exclusive mode.
+ */
+static XLogRecPtr
+SetLastWrittenLSNForBlockRangeInternal(XLogRecPtr lsn,
+									   NRelFileInfo rlocator,
+									   ForkNumber forknum,
+									   BlockNumber from,
+									   BlockNumber n_blocks)
+{
+	if (NInfoGetRelNumber(rlocator) == InvalidOid)
+	{
+		if (lsn > LwLsnCache->maxLastWrittenLsn)
+		LwLsnCache->maxLastWrittenLsn = lsn;
+		else
+			lsn = LwLsnCache->maxLastWrittenLsn;
+	}
+	else
+	{
+		LastWrittenLsnCacheEntry* entry;
+		BufferTag key;
+		bool found;
+		BlockNumber i;
+
+		Oid spcOid = NInfoGetSpcOid(rlocator);
+		Oid dbOid = NInfoGetDbOid(rlocator);
+		Oid relNumber = NInfoGetRelNumber(rlocator);
+		BufTagInit(key,  relNumber, forknum, from, spcOid, dbOid);
+		for (i = 0; i < n_blocks; i++)
+		{
+			key.blockNum = from + i;
+			entry = hash_search(lastWrittenLsnCache, &key, HASH_ENTER, &found);
+			if (found)
+			{
+				if (lsn > entry->lsn)
+					entry->lsn = lsn;
+				else
+					lsn = entry->lsn;
+				/* Unlink from LRU list */
+				dlist_delete(&entry->lru_node);
+			}
+			else
+			{
+				entry->lsn = lsn;
+				if (hash_get_num_entries(lastWrittenLsnCache) > LwLsnCache->lastWrittenLsnCacheSize)
+				{
+					/* Replace least recently used entry */
+					LastWrittenLsnCacheEntry* victim = dlist_container(LastWrittenLsnCacheEntry, lru_node, dlist_pop_head_node(&LwLsnCache->lastWrittenLsnLRU));
+					/* Adjust max LSN for not cached relations/chunks if needed */
+					if (victim->lsn > LwLsnCache->maxLastWrittenLsn)
+					LwLsnCache->maxLastWrittenLsn = victim->lsn;
+
+					hash_search(lastWrittenLsnCache, victim, HASH_REMOVE, NULL);
+				}
+			}
+			/* Link to the end of LRU list */
+			dlist_push_tail(&LwLsnCache->lastWrittenLsnLRU, &entry->lru_node);
+		}
+	}
+	return lsn;
+}
+
+/*
+ * SetLastWrittenLSNForBlockRange -- Set maximal LSN of written page range.
+ * We maintain cache of last written LSNs with limited size and LRU replacement
+ * policy. Keeping last written LSN for each page allows to use old LSN when
+ * requesting pages of unchanged or appended relations. Also it is critical for
+ * efficient work of prefetch in case massive update operations (like vacuum or remove).
+ *
+ * rlocator.relNumber can be InvalidOid, in this case maxLastWrittenLsn is updated.
+ * SetLastWrittenLsn with dummy rlocator is used by createdb and dbase_redo functions.
+ */
+XLogRecPtr
+neon_set_lwlsn_block_range(XLogRecPtr lsn, NRelFileInfo rlocator, ForkNumber forknum, BlockNumber from, BlockNumber n_blocks)
+{
+	if (lsn == InvalidXLogRecPtr || n_blocks == 0 || LwLsnCache->lastWrittenLsnCacheSize == 0)
+		return lsn;
+
+	LWLockAcquire(LastWrittenLsnLock, LW_EXCLUSIVE);
+	lsn = SetLastWrittenLSNForBlockRangeInternal(lsn, rlocator, forknum, from, n_blocks);
+	LWLockRelease(LastWrittenLsnLock);
+
+	return lsn;
+}
+
+/*
+ * neon_set_lwlsn_block_v -- Set maximal LSN of pages to their respective
+ * LSNs.
+ *
+ * We maintain cache of last written LSNs with limited size and LRU replacement
+ * policy. Keeping last written LSN for each page allows to use old LSN when
+ * requesting pages of unchanged or appended relations. Also it is critical for
+ * efficient work of prefetch in case massive update operations (like vacuum or remove).
+ *
+ * Note: This is different from SetLastWrittenLSNForBlockRange[Internal], in that this
+ * specifies per-block LSNs, rather than only a single LSN.
+ */
+XLogRecPtr
+neon_set_lwlsn_block_v(const XLogRecPtr *lsns, NRelFileInfo relfilenode,
+						   ForkNumber forknum, BlockNumber blockno,
+						   int nblocks)
+{
+	LastWrittenLsnCacheEntry* entry;
+	BufferTag	key;
+	bool		found;
+	XLogRecPtr	max = InvalidXLogRecPtr;
+	Oid spcOid = NInfoGetSpcOid(relfilenode);
+	Oid dbOid = NInfoGetDbOid(relfilenode);
+	Oid relNumber = NInfoGetRelNumber(relfilenode);
+
+	if (lsns == NULL || nblocks == 0 || LwLsnCache->lastWrittenLsnCacheSize == 0 ||
+		NInfoGetRelNumber(relfilenode) == InvalidOid)
+		return InvalidXLogRecPtr;
+
+	
+	BufTagInit(key,  relNumber, forknum, blockno, spcOid, dbOid);
+
+	LWLockAcquire(LastWrittenLsnLock, LW_EXCLUSIVE);
+
+	for (int i = 0; i < nblocks; i++)
+	{
+		XLogRecPtr	lsn = lsns[i];
+
+		key.blockNum = blockno + i;
+		entry = hash_search(lastWrittenLsnCache, &key, HASH_ENTER, &found);
+		if (found)
+		{
+			if (lsn > entry->lsn)
+				entry->lsn = lsn;
+			else
+				lsn = entry->lsn;
+			/* Unlink from LRU list */
+			dlist_delete(&entry->lru_node);
+		}
+		else
+		{
+			entry->lsn = lsn;
+			if (hash_get_num_entries(lastWrittenLsnCache) > LwLsnCache->lastWrittenLsnCacheSize)
+			{
+				/* Replace least recently used entry */
+				LastWrittenLsnCacheEntry* victim = dlist_container(LastWrittenLsnCacheEntry, lru_node, dlist_pop_head_node(&LwLsnCache->lastWrittenLsnLRU));
+				/* Adjust max LSN for not cached relations/chunks if needed */
+				if (victim->lsn > LwLsnCache->maxLastWrittenLsn)
+					LwLsnCache->maxLastWrittenLsn = victim->lsn;
+
+				hash_search(lastWrittenLsnCache, victim, HASH_REMOVE, NULL);
+			}
+		}
+		/* Link to the end of LRU list */
+		dlist_push_tail(&LwLsnCache->lastWrittenLsnLRU, &entry->lru_node);
+		max = Max(max, lsn);
+	}
+
+	LWLockRelease(LastWrittenLsnLock);
+
+	return max;
+}
+
+/*
+ * SetLastWrittenLSNForBlock -- Set maximal LSN for block
+ */
+XLogRecPtr
+neon_set_lwlsn_block(XLogRecPtr lsn, NRelFileInfo rlocator, ForkNumber forknum, BlockNumber blkno)
+{
+	return neon_set_lwlsn_block_range(lsn, rlocator, forknum, blkno, 1);
+}
+
+/*
+ * neon_set_lwlsn_relation -- Set maximal LSN for relation metadata
+ */
+XLogRecPtr
+neon_set_lwlsn_relation(XLogRecPtr lsn, NRelFileInfo rlocator, ForkNumber forknum)
+{
+	return neon_set_lwlsn_block(lsn, rlocator, forknum, REL_METADATA_PSEUDO_BLOCKNO);
+}
+
+/*
+ * neon_set_lwlsn_db -- Set maximal LSN for the whole database
+ */
+XLogRecPtr
+neon_set_lwlsn_db(XLogRecPtr lsn)
+{
+	NRelFileInfo dummyNode = {InvalidOid, InvalidOid, InvalidOid};
+	return neon_set_lwlsn_block(lsn, dummyNode, MAIN_FORKNUM, 0);
+}

pgxn/neon/neon_lwlsncache.h

@@ -0,0 +1,17 @@
+#ifndef NEON_LWLSNCACHE_H
+#define NEON_LWLSNCACHE_H
+
+#include "neon_pgversioncompat.h"
+
+void init_lwlsncache(void);
+
+/* Hooks */
+XLogRecPtr neon_get_lwlsn(NRelFileInfo rlocator, ForkNumber forknum, BlockNumber blkno);
+void neon_get_lwlsn_v(NRelFileInfo relfilenode, ForkNumber forknum, BlockNumber blkno, int nblocks, XLogRecPtr *lsns);
+XLogRecPtr neon_set_lwlsn_block_range(XLogRecPtr lsn, NRelFileInfo rlocator, ForkNumber forknum, BlockNumber from, BlockNumber n_blocks);
+XLogRecPtr neon_set_lwlsn_block_v(const XLogRecPtr *lsns, NRelFileInfo relfilenode, ForkNumber forknum, BlockNumber blockno, int nblocks);
+XLogRecPtr neon_set_lwlsn_block(XLogRecPtr lsn, NRelFileInfo rlocator, ForkNumber forknum, BlockNumber blkno);
+XLogRecPtr neon_set_lwlsn_relation(XLogRecPtr lsn, NRelFileInfo rlocator, ForkNumber forknum);
+XLogRecPtr neon_set_lwlsn_db(XLogRecPtr lsn);
+
+#endif /* NEON_LWLSNCACHE_H */

pgxn/neon/neon_pgversioncompat.h

@@ -76,6 +76,14 @@ InitBufferTag(BufferTag *tag, const RelFileNode *rnode,
 
 #define BufTagGetRelNumber(tagp) ((tagp)->rnode.relNode)
 
+#define BufTagInit(tag, relNumber, forknum, blkno, spcOid, dbOid) \
+	do { \
+		RelFileNode rnode = { .spcNode = spcOid, .dbNode = dbOid, .relNode = relNumber}; \
+		(tag).forkNum = forknum; \
+		(tag).blockNum = blkno; \
+		(tag).rnode = rnode; \
+	} while (false)
+
 #define InvalidRelFileNumber InvalidOid
 
 #define SMgrRelGetRelInfo(reln) \
@@ -125,6 +133,15 @@ InitBufferTag(BufferTag *tag, const RelFileNode *rnode,
 		.relNumber = (tag).relNumber, \
 	})
 
+#define BufTagInit(tag, relNumber, forknum, blkno, spcOid, dbOid) \
+	do { \
+		(tag).forkNum = forknum; \
+		(tag).blockNum = blkno; \
+		(tag).spcOid = spcOid; \
+		(tag).dbOid = dbOid; \
+		(tag).relNumber = relNumber; \
+	} while (false)
+
 #define SMgrRelGetRelInfo(reln) \
 	((reln)->smgr_rlocator)
 

pgxn/neon/pagestore_smgr.c

@@ -69,6 +69,7 @@
 
 #include "bitmap.h"
 #include "neon.h"
+#include "neon_lwlsncache.h"
 #include "neon_perf_counters.h"
 #include "pagestore_client.h"
 
@@ -340,11 +341,6 @@ static void prefetch_do_request(PrefetchRequest *slot, neon_request_lsns *force_
 static bool prefetch_wait_for(uint64 ring_index);
 static void prefetch_cleanup_trailing_unused(void);
 static inline void prefetch_set_unused(uint64 ring_index);
-#if PG_MAJORVERSION_NUM < 17
-static void
-GetLastWrittenLSNv(NRelFileInfo relfilenode, ForkNumber forknum,
-				   BlockNumber blkno, int nblocks, XLogRecPtr *lsns);
-#endif
 
 static void
 neon_get_request_lsns(NRelFileInfo rinfo, ForkNumber forknum,
@@ -1997,7 +1993,7 @@ neon_wallog_pagev(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 
 		if (batch_size >= BLOCK_BATCH_SIZE)
 		{
-			SetLastWrittenLSNForBlockv(lsns, InfoFromSMgrRel(reln), forknum,
+			neon_set_lwlsn_block_v(lsns, InfoFromSMgrRel(reln), forknum,
 									   batch_blockno,
 									   batch_size);
 			batch_blockno += batch_size;
@@ -2007,7 +2003,7 @@ neon_wallog_pagev(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 
 	if (batch_size != 0)
 	{
-		SetLastWrittenLSNForBlockv(lsns, InfoFromSMgrRel(reln), forknum,
+		neon_set_lwlsn_block_v(lsns, InfoFromSMgrRel(reln), forknum,
 								   batch_blockno,
 								   batch_size);
 	}
@@ -2134,7 +2130,7 @@ neon_wallog_page(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, co
 	 * Remember the LSN on this page. When we read the page again, we must
 	 * read the same or newer version of it.
 	 */
-	SetLastWrittenLSNForBlock(lsn, InfoFromSMgrRel(reln), forknum, blocknum);
+	neon_set_lwlsn_block(lsn, InfoFromSMgrRel(reln), forknum, blocknum);
 }
 
 /*
@@ -2217,19 +2213,6 @@ nm_adjust_lsn(XLogRecPtr lsn)
 }
 
 
-/*
- * Since PG17 we use vetorized version,
- * so add compatibility function for older versions
- */
-#if PG_MAJORVERSION_NUM < 17
-static void
-GetLastWrittenLSNv(NRelFileInfo relfilenode, ForkNumber forknum,
-				   BlockNumber blkno, int nblocks, XLogRecPtr *lsns)
-{
-	lsns[0] = GetLastWrittenLSN(relfilenode, forknum, blkno);
-}
-#endif
-
 /*
  * Return LSN for requesting pages and number of blocks from page server
  */
@@ -2241,7 +2224,7 @@ neon_get_request_lsns(NRelFileInfo rinfo, ForkNumber forknum, BlockNumber blkno,
 
 	Assert(nblocks <= PG_IOV_MAX);
 
-	GetLastWrittenLSNv(rinfo, forknum, blkno, (int) nblocks, last_written_lsns);
+	neon_get_lwlsn_v(rinfo, forknum, blkno, (int) nblocks, last_written_lsns);
 
 	for (int i = 0; i < nblocks; i++)
 	{
@@ -2844,9 +2827,9 @@ neon_extend(SMgrRelation reln, ForkNumber forkNum, BlockNumber blkno,
 	if (lsn == InvalidXLogRecPtr)
 	{
 		lsn = GetXLogInsertRecPtr();
-		SetLastWrittenLSNForBlock(lsn, InfoFromSMgrRel(reln), forkNum, blkno);
+		neon_set_lwlsn_block(lsn, InfoFromSMgrRel(reln), forkNum, blkno);
 	}
-	SetLastWrittenLSNForRelation(lsn, InfoFromSMgrRel(reln), forkNum);
+	neon_set_lwlsn_relation(lsn, InfoFromSMgrRel(reln), forkNum);
 }
 
 #if PG_MAJORVERSION_NUM >= 16
@@ -2941,7 +2924,7 @@ neon_zeroextend(SMgrRelation reln, ForkNumber forkNum, BlockNumber blocknum,
 		for (int i = 0; i < count; i++)
 		{
 			lfc_write(InfoFromSMgrRel(reln), forkNum, blocknum + i, buffer.data);
-			SetLastWrittenLSNForBlock(lsn, InfoFromSMgrRel(reln), forkNum,
+			neon_set_lwlsn_block(lsn, InfoFromSMgrRel(reln), forkNum,
 									  blocknum + i);
 		}
 
@@ -2951,7 +2934,7 @@ neon_zeroextend(SMgrRelation reln, ForkNumber forkNum, BlockNumber blocknum,
 
 	Assert(lsn != 0);
 
-	SetLastWrittenLSNForRelation(lsn, InfoFromSMgrRel(reln), forkNum);
+	neon_set_lwlsn_relation(lsn, InfoFromSMgrRel(reln), forkNum);
 	set_cached_relsize(InfoFromSMgrRel(reln), forkNum, blocknum);
 }
 #endif
@@ -4052,7 +4035,7 @@ neon_truncate(SMgrRelation reln, ForkNumber forknum, BlockNumber old_blocks, Blo
 	 * for the extended pages, so there's no harm in leaving behind obsolete
 	 * entries for the truncated chunks.
 	 */
-	SetLastWrittenLSNForRelation(lsn, InfoFromSMgrRel(reln), forknum);
+	neon_set_lwlsn_relation(lsn, InfoFromSMgrRel(reln), forknum);
 
 #ifdef DEBUG_COMPARE_LOCAL
 	if (IS_LOCAL_REL(reln))
@@ -4510,7 +4493,7 @@ neon_extend_rel_size(NRelFileInfo rinfo, ForkNumber forknum, BlockNumber blkno,
 		if (relsize < blkno + 1)
 		{
 			update_cached_relsize(rinfo, forknum, blkno + 1);
-			SetLastWrittenLSNForRelation(end_recptr, rinfo, forknum);
+			neon_set_lwlsn_relation(end_recptr, rinfo, forknum);
 		}
 	}
 	else
@@ -4543,7 +4526,7 @@ neon_extend_rel_size(NRelFileInfo rinfo, ForkNumber forknum, BlockNumber blkno,
 		relsize = Max(nbresponse->n_blocks, blkno + 1);
 
 		set_cached_relsize(rinfo, forknum, relsize);
-		SetLastWrittenLSNForRelation(end_recptr, rinfo, forknum);
+		neon_set_lwlsn_relation(end_recptr, rinfo, forknum);
 
 		neon_log(SmgrTrace, "Set length to %d", relsize);
 	}
@@ -4674,7 +4657,7 @@ neon_redo_read_buffer_filter(XLogReaderState *record, uint8 block_id)
 	 */
 	if (no_redo_needed)
 	{
-		SetLastWrittenLSNForBlock(end_recptr, rinfo, forknum, blkno);
+		neon_set_lwlsn_block(end_recptr, rinfo, forknum, blkno);
 		/*
 		 * Redo changes if page exists in LFC.
 		 * We should perform this check after assigning LwLSN to prevent

pgxn/neon_walredo/walredoproc.c

@@ -286,9 +286,6 @@ WalRedoMain(int argc, char *argv[])
 	max_wal_senders = 0;
 	InitializeMaxBackends();
 
-	/* Disable lastWrittenLsnCache */
-	lastWrittenLsnCacheSize = 0;
-
 #if PG_VERSION_NUM >= 150000
 	process_shmem_requests();
 	InitializeShmemGUCs();

vendor/revisions.json

@@ -1,18 +1,18 @@
 {
   "v17": [
     "17.4",
-    "e5e87b9f52d0eaeb83f3e2517bb9727aac37729b"
+    "22533c63fc42cdc1dbe138650ba1eca10a70c5d7"
   ],
   "v16": [
     "16.8",
-    "512856aaa8bedbaa8f06811449518dcb0c2e5d8f"
+    "473f68210d52ff8508f71c15b0c77c01296f4ace"
   ],
   "v15": [
     "15.12",
-    "ee794ba767eef9b10260ef67d3a58084f1dabd6f"
+    "6cea02e23caa950d5f06932491a91b6af8f54360"
   ],
   "v14": [
     "14.17",
-    "7b7592e74059f795b64f06860cea97673418f35e"
+    "35bc1b0cba55680e3b37abce4e67a46bb15f3315"
   ]
 }