reftable/merged: split up initialization and seeking of records

To initialize a `struct merged_iter`, we need to seek all subiterators
to the wanted record and then add their results to the priority queue
used to sort the records. This logic is split up across two functions,
`merged_table_seek_record()` and `merged_iter_init()`. The scope of
these functions is somewhat weird though, where `merged_iter_init()` is
only responsible for adding the records of the subiterators to the
priority queue.

Clarify the scope of those functions such that `merged_iter_init()` is
only responsible for initializing the iterator's structure. Performing
the subiterator seeks are now part of `merged_table_seek_record()`.

This step is required to move seeking of records into the generic
`struct reftable_iterator` infrastructure.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

reftable/merged.c

@@ -25,34 +25,18 @@ struct merged_subiter {
 struct merged_iter {
 	struct merged_subiter *subiters;
 	struct merged_iter_pqueue pq;
-	uint32_t hash_id;
 	size_t stack_len;
-	uint8_t typ;
 	int suppress_deletions;
 	ssize_t advance_index;
 };
 
-static int merged_iter_init(struct merged_iter *mi)
+static void merged_iter_init(struct merged_iter *mi,
+			     struct reftable_merged_table *mt)
 {
-	for (size_t i = 0; i < mi->stack_len; i++) {
-		struct pq_entry e = {
-			.index = i,
-			.rec = &mi->subiters[i].rec,
-		};
-		int err;
-
-		reftable_record_init(&mi->subiters[i].rec, mi->typ);
-		err = iterator_next(&mi->subiters[i].iter,
-				    &mi->subiters[i].rec);
-		if (err < 0)
-			return err;
-		if (err > 0)
-			continue;
-
-		merged_iter_pqueue_add(&mi->pq, &e);
-	}
-
-	return 0;
+	memset(mi, 0, sizeof(*mi));
+	mi->advance_index = -1;
+	mi->suppress_deletions = mt->suppress_deletions;
+	REFTABLE_CALLOC_ARRAY(mi->subiters, mt->stack_len);
 }
 
 static void merged_iter_close(void *p)
@@ -246,32 +230,33 @@ static int merged_table_seek_record(struct reftable_merged_table *mt,
 				    struct reftable_iterator *it,
 				    struct reftable_record *rec)
 {
-	struct merged_iter merged = {
-		.typ = reftable_record_type(rec),
-		.hash_id = mt->hash_id,
-		.suppress_deletions = mt->suppress_deletions,
-		.advance_index = -1,
-	};
-	struct merged_iter *p;
+	struct merged_iter merged, *p;
 	int err;
 
-	REFTABLE_CALLOC_ARRAY(merged.subiters, mt->stack_len);
+	merged_iter_init(&merged, mt);
+
 	for (size_t i = 0; i < mt->stack_len; i++) {
+		reftable_record_init(&merged.subiters[merged.stack_len].rec,
+				     reftable_record_type(rec));
+
 		err = reftable_table_seek_record(&mt->stack[i],
 						 &merged.subiters[merged.stack_len].iter, rec);
 		if (err < 0)
 			goto out;
-		if (!err)
-			merged.stack_len++;
-	}
+		if (err > 0)
+			continue;
 
-	err = merged_iter_init(&merged);
-	if (err < 0)
-		goto out;
+		err = merged_iter_advance_subiter(&merged, merged.stack_len);
+		if (err < 0)
+			goto out;
+
+		merged.stack_len++;
+	}
 
-	p = reftable_malloc(sizeof(struct merged_iter));
+	p = reftable_malloc(sizeof(*p));
 	*p = merged;
 	iterator_from_merged_iter(it, p);
+	err = 0;
 
 out:
 	if (err < 0)