diff --git a/src/scan_iterator.c b/src/scan_iterator.c
index f2a1d6e06dc..2b2dd45e7b1 100644
--- a/src/scan_iterator.c
+++ b/src/scan_iterator.c
@@ -44,7 +44,7 @@ ts_scan_iterator_scan_key_init(ScanIterator *iterator, AttrNumber attributeNumbe
 	 * sure the scan key is initialized on the long-lived scankey memory
 	 * context.
 	 */
-	oldmcxt = MemoryContextSwitchTo(iterator->scankey_mcxt);
+	oldmcxt = MemoryContextSwitchTo(iterator->ctx.internal.scan_mcxt);
 	ScanKeyInit(&iterator->scankey[iterator->ctx.nkeys++],
 				attributeNumber,
 				strategy,
@@ -56,7 +56,5 @@ ts_scan_iterator_scan_key_init(ScanIterator *iterator, AttrNumber attributeNumbe
 TSDLLEXPORT void
 ts_scan_iterator_rescan(ScanIterator *iterator)
 {
-	MemoryContext oldmcxt = MemoryContextSwitchTo(iterator->scankey_mcxt);
 	ts_scanner_rescan(&iterator->ctx, NULL);
-	MemoryContextSwitchTo(oldmcxt);
 }
diff --git a/src/scan_iterator.h b/src/scan_iterator.h
index 099e781f94c..42ba300b07f 100644
--- a/src/scan_iterator.h
+++ b/src/scan_iterator.h
@@ -18,7 +18,6 @@ typedef struct ScanIterator
 {
 	ScannerCtx ctx;
 	TupleInfo *tinfo;
-	MemoryContext scankey_mcxt;
 	ScanKeyData scankey[EMBEDDED_SCAN_KEY_SIZE];
 } ScanIterator;
 
@@ -28,6 +27,7 @@ typedef struct ScanIterator
 		.ctx = {                                                                                   \
 			.internal = {													\
 				.ended = true,											\
+				.scan_mcxt = CurrentMemoryContext,						\
 			},															\
 			.table = catalog_get_table_id(ts_catalog_get(), catalog_table_id),                     \
 			.nkeys = 0,                                                                            \
@@ -35,8 +35,7 @@ typedef struct ScanIterator
 			.lockmode = lock_mode,                                                                 \
 			.result_mctx = mctx,                                                                   \
 			.flags = SCANNER_F_NOFLAGS,									\
-		},																\
-		.scankey_mcxt = CurrentMemoryContext, \
+		}, \
 	}
 
 static inline TupleInfo *
@@ -78,9 +77,7 @@ ts_scan_iterator_alloc_result(const ScanIterator *iterator, Size size)
 static inline void
 ts_scan_iterator_start_scan(ScanIterator *iterator)
 {
-	MemoryContext oldmcxt = MemoryContextSwitchTo(iterator->scankey_mcxt);
 	ts_scanner_start_scan(&(iterator)->ctx);
-	MemoryContextSwitchTo(oldmcxt);
 }
 
 static inline TupleInfo *
diff --git a/src/scanner.c b/src/scanner.c
index 84e98561751..e04241e7270 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -172,13 +172,16 @@ TSDLLEXPORT void
 ts_scanner_rescan(ScannerCtx *ctx, const ScanKey scankey)
 {
 	Scanner *scanner = scanner_ctx_get_scanner(ctx);
+	MemoryContext oldmcxt;
 
 	/* If scankey is NULL, the existing scan key was already updated or the
 	 * old should be reused */
 	if (NULL != scankey)
 		memcpy(ctx->scankey, scankey, sizeof(*ctx->scankey));
 
+	oldmcxt = MemoryContextSwitchTo(ctx->internal.scan_mcxt);
 	scanner->rescan(ctx);
+	MemoryContextSwitchTo(oldmcxt);
 }
 
 static void
@@ -187,6 +190,9 @@ prepare_scan(ScannerCtx *ctx)
 	ctx->internal.ended = false;
 	ctx->internal.registered_snapshot = false;
 
+	if (ctx->internal.scan_mcxt == NULL)
+		ctx->internal.scan_mcxt = CurrentMemoryContext;
+
 	if (ctx->snapshot == NULL)
 	{
 		/*
@@ -213,8 +219,10 @@ prepare_scan(ScannerCtx *ctx)
 		 * hypertables compared to regular tables under SERIALIZABLE
 		 * mode.
 		 */
+		MemoryContext oldmcxt = MemoryContextSwitchTo(ctx->internal.scan_mcxt);
 		ctx->snapshot = RegisterSnapshot(GetSnapshotData(SnapshotSelf));
 		ctx->internal.registered_snapshot = true;
+		MemoryContextSwitchTo(oldmcxt);
 	}
 }
 
@@ -222,11 +230,18 @@ TSDLLEXPORT Relation
 ts_scanner_open(ScannerCtx *ctx)
 {
 	Scanner *scanner = scanner_ctx_get_scanner(ctx);
+	MemoryContext oldmcxt;
+	Relation rel;
 
 	Assert(NULL == ctx->tablerel);
+
 	prepare_scan(ctx);
+	Assert(ctx->internal.scan_mcxt != NULL);
+	oldmcxt = MemoryContextSwitchTo(ctx->internal.scan_mcxt);
+	rel = scanner->openscan(ctx);
+	MemoryContextSwitchTo(oldmcxt);
 
-	return scanner->openscan(ctx);
+	return rel;
 }
 
 /*
@@ -240,6 +255,7 @@ ts_scanner_start_scan(ScannerCtx *ctx)
 	InternalScannerCtx *ictx = &ctx->internal;
 	Scanner *scanner;
 	TupleDesc tuple_desc;
+	MemoryContext oldmcxt;
 
 	if (ictx->started)
 	{
@@ -269,6 +285,9 @@ ts_scanner_start_scan(ScannerCtx *ctx)
 			ctx->index = RelationGetRelid(ctx->indexrel);
 	}
 
+	Assert(ctx->internal.scan_mcxt != NULL);
+	oldmcxt = MemoryContextSwitchTo(ctx->internal.scan_mcxt);
+
 	scanner = scanner_ctx_get_scanner(ctx);
 	scanner->beginscan(ctx);
 
@@ -277,6 +296,7 @@ ts_scanner_start_scan(ScannerCtx *ctx)
 	ictx->tinfo.scanrel = ctx->tablerel;
 	ictx->tinfo.mctx = ctx->result_mctx == NULL ? CurrentMemoryContext : ctx->result_mctx;
 	ictx->tinfo.slot = MakeSingleTupleTableSlot(tuple_desc, table_slot_callbacks(ctx->tablerel));
+	MemoryContextSwitchTo(oldmcxt);
 
 	/* Call pre-scan handler, if any. */
 	if (ctx->prescan != NULL)
@@ -307,6 +327,11 @@ scanner_cleanup(ScannerCtx *ctx)
 		ExecDropSingleTupleTableSlot(ictx->tinfo.slot);
 		ictx->tinfo.slot = NULL;
 	}
+
+	if (NULL != ictx->scan_mcxt)
+	{
+		ictx->scan_mcxt = NULL;
+	}
 }
 
 TSDLLEXPORT void
@@ -314,6 +339,7 @@ ts_scanner_end_scan(ScannerCtx *ctx)
 {
 	InternalScannerCtx *ictx = &ctx->internal;
 	Scanner *scanner = scanner_ctx_get_scanner(ctx);
+	MemoryContext oldmcxt;
 
 	if (ictx->ended)
 		return;
@@ -322,7 +348,10 @@ ts_scanner_end_scan(ScannerCtx *ctx)
 	if (ctx->postscan != NULL)
 		ctx->postscan(ictx->tinfo.count, ctx->data);
 
+	oldmcxt = MemoryContextSwitchTo(ctx->internal.scan_mcxt);
 	scanner->endscan(ctx);
+	MemoryContextSwitchTo(oldmcxt);
+
 	scanner_cleanup(ctx);
 	ictx->ended = true;
 	ictx->started = false;
@@ -348,7 +377,14 @@ ts_scanner_next(ScannerCtx *ctx)
 {
 	InternalScannerCtx *ictx = &ctx->internal;
 	Scanner *scanner = scanner_ctx_get_scanner(ctx);
-	bool is_valid = ts_scanner_limit_reached(ctx) ? false : scanner->getnext(ctx);
+	bool is_valid = false;
+
+	if (!ts_scanner_limit_reached(ctx))
+	{
+		MemoryContext oldmcxt = MemoryContextSwitchTo(ctx->internal.scan_mcxt);
+		is_valid = scanner->getnext(ctx);
+		MemoryContextSwitchTo(oldmcxt);
+	}
 
 	while (is_valid)
 	{
@@ -375,7 +411,15 @@ ts_scanner_next(ScannerCtx *ctx)
 			/* stop at a valid tuple */
 			return &ictx->tinfo;
 		}
-		is_valid = ts_scanner_limit_reached(ctx) ? false : scanner->getnext(ctx);
+
+		if (ts_scanner_limit_reached(ctx))
+			is_valid = false;
+		else
+		{
+			MemoryContext oldmcxt = MemoryContextSwitchTo(ctx->internal.scan_mcxt);
+			is_valid = scanner->getnext(ctx);
+			MemoryContextSwitchTo(oldmcxt);
+		}
 	}
 
 	if (!(ctx->flags & SCANNER_F_NOEND))
diff --git a/src/scanner.h b/src/scanner.h
index a74e52023ef..6cbf5d90057 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -85,6 +85,12 @@ typedef struct InternalScannerCtx
 {
 	TupleInfo tinfo;
 	ScanDesc scan;
+	/*
+	 * PG scan functions must be called on a memory context that lives
+	 * throughout the entire scan. Use the scan_mcxt to ensure that
+	 * functions aren't called on, e.g., a per-tuple context.
+	 */
+	MemoryContext scan_mcxt;
 	bool registered_snapshot;
 	bool started;
 	bool ended;
diff --git a/src/telemetry/stats.c b/src/telemetry/stats.c
index 35084e16697..264bb9d89eb 100644
--- a/src/telemetry/stats.c
+++ b/src/telemetry/stats.c
@@ -338,13 +338,10 @@ get_chunk_compression_stats(StatsContext *statsctx, const Chunk *chunk,
 							Form_compression_chunk_size compr_stats)
 {
 	TupleInfo *ti;
-	MemoryContext oldmcxt;
 
 	if (!ts_chunk_is_compressed(chunk))
 		return false;
 
-	/* Need to execute the scan functions on the long-lived memory context */
-	oldmcxt = MemoryContextSwitchTo(statsctx->compressed_chunk_stats_iterator.scankey_mcxt);
 	ts_scan_iterator_scan_key_reset(&statsctx->compressed_chunk_stats_iterator);
 	ts_scan_iterator_scan_key_init(&statsctx->compressed_chunk_stats_iterator,
 								   Anum_compression_chunk_size_pkey_chunk_id,
@@ -353,7 +350,6 @@ get_chunk_compression_stats(StatsContext *statsctx, const Chunk *chunk,
 								   Int32GetDatum(chunk->fd.id));
 	ts_scan_iterator_start_or_restart_scan(&statsctx->compressed_chunk_stats_iterator);
 	ti = ts_scan_iterator_next(&statsctx->compressed_chunk_stats_iterator);
-	MemoryContextSwitchTo(oldmcxt);
 
 	if (ti)
 	{