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[PATCH 08/13] reftable/merged: simplify indices for subiterators

From
Patrick Steinhardt <ps@pks.im>
Date
May 8, 2024, 11:04 UTC
Message-ID
<f0f42cd56b9e54e9c7d58be41fcc4e226d5c76ff.1715166175.git.ps@pks.im>
In-Reply-To
<cover.1715166175.git.ps@pks.im>

When seeking on a merged table, we perform the seek for each of the subiterators. If the subiterator hasa the desired record we add it to the priority queue, otherwise we skip it and don't add it to the stack of subiterators hosted by the merged table.

The consequence of this is that the index of the subiterator in the merged table does not necessarily correspond to the index of it in the merged iterator. Next to being potentially confusing, it also means that we won't easily be able to re-seek the merged iterator because we have no clear connection between both of the data structures.

Refactor the code so that the index stays the same in both structures.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 reftable/merged.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/reftable/merged.c b/reftable/merged.c
index 4e1b78e93f..18a2a6f09b 100644
--- a/reftable/merged.c
+++ b/reftable/merged.c
@@ -37,6 +37,7 @@ static void merged_iter_init(struct merged_iter *mi,
 	mi->advance_index = -1;
 	mi->suppress_deletions = mt->suppress_deletions;
 	REFTABLE_CALLOC_ARRAY(mi->subiters, mt->stack_len);
+	mi->stack_len = mt->stack_len;
 }
 
 static void merged_iter_close(void *p)
@@ -236,21 +237,19 @@ static int merged_table_seek_record(struct reftable_merged_table *mt,
 	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_init(&merged.subiters[i].rec,
 				     reftable_record_type(rec));
 
 		err = reftable_table_seek_record(&mt->stack[i],
-						 &merged.subiters[merged.stack_len].iter, rec);
+						 &merged.subiters[i].iter, rec);
 		if (err < 0)
 			goto out;
 		if (err > 0)
 			continue;
 
-		err = merged_iter_advance_subiter(&merged, merged.stack_len);
+		err = merged_iter_advance_subiter(&merged, i);
 		if (err < 0)
 			goto out;
-
-		merged.stack_len++;
 	}
 
 	p = reftable_malloc(sizeof(*p));
-- 
2.45.0
Previous: Patrick SteinhardtNext: Justin Tobler
Message 11 of 50 in “reftable: prepare for re-seekable iterators”
  1. 00/13 reftable: prepare for re-seekable iteratorsPatrick Steinhardt, May 8, 2024
  2. 01/13 reftable/block: use `size_t` to track restart point indexPatrick Steinhardt, May 8, 2024
  3. 02/13 reftable/reader: avoid copying index iteratorPatrick Steinhardt, May 8, 2024
  4. 03/13 reftable/reader: unify indexed and linear seekingPatrick Steinhardt, May 8, 2024
  5. 04/13 reftable/reader: separate concerns of table iter and reftable readerPatrick Steinhardt, May 8, 2024
  6. 05/13 reftable/reader: inline `reader_seek_internal()`Patrick Steinhardt, May 8, 2024
  7. 06/13 reftable/reader: set up the reader when initializing table iteratorPatrick Steinhardt, May 8, 2024
  8. 07/13 reftable/merged: split up initialization and seeking of recordsPatrick Steinhardt, May 8, 2024
  9. Justin ToblerMay 10, 2024
  10. Patrick SteinhardtMay 13, 2024
  11. 08/13 reftable/merged: simplify indices for subiteratorsPatrick Steinhardt, May 8, 2024
  12. Justin ToblerMay 10, 2024
  13. Patrick SteinhardtMay 13, 2024
  14. 09/13 reftable/generic: move seeking of records into the iteratorPatrick Steinhardt, May 8, 2024
  15. Justin ToblerMay 10, 2024
  16. Patrick SteinhardtMay 13, 2024
  17. 10/13 reftable/generic: adapt interface to allow reuse of iteratorsPatrick Steinhardt, May 8, 2024
  18. 11/13 reftable/reader: adapt interface to allow reuse of iteratorsPatrick Steinhardt, May 8, 2024
  19. Justin ToblerMay 10, 2024
  20. Patrick SteinhardtMay 13, 2024
  21. 12/13 reftable/stack: provide convenience functions to create iteratorsPatrick Steinhardt, May 8, 2024
  22. 13/13 reftable/merged: adapt interface to allow reuse of iteratorsPatrick Steinhardt, May 8, 2024
  23. Junio C HamanoMay 8, 2024
  24. Junio C HamanoMay 9, 2024
  25. Patrick SteinhardtMay 10, 2024
  26. Junio C HamanoMay 10, 2024
  27. Patrick SteinhardtMay 10, 2024
  28. Junio C HamanoMay 10, 2024
  29. 00/13 reftable: prepare for re-seekable iteratorsPatrick Steinhardt, May 13, 2024
  30. 01/13 reftable/block: use `size_t` to track restart point indexPatrick Steinhardt, May 13, 2024
  31. Karthik NayakMay 21, 2024
  32. Patrick SteinhardtMay 22, 2024
  33. 02/13 reftable/reader: avoid copying index iteratorPatrick Steinhardt, May 13, 2024
  34. 03/13 reftable/reader: unify indexed and linear seekingPatrick Steinhardt, May 13, 2024
  35. Karthik NayakMay 21, 2024
  36. Patrick SteinhardtMay 22, 2024
  37. Karthik NayakMay 22, 2024
  38. 04/13 reftable/reader: separate concerns of table iter and reftable readerPatrick Steinhardt, May 13, 2024
  39. 05/13 reftable/reader: inline `reader_seek_internal()`Patrick Steinhardt, May 13, 2024
  40. 06/13 reftable/reader: set up the reader when initializing table iteratorPatrick Steinhardt, May 13, 2024
  41. 07/13 reftable/merged: split up initialization and seeking of recordsPatrick Steinhardt, May 13, 2024
  42. 08/13 reftable/merged: simplify indices for subiteratorsPatrick Steinhardt, May 13, 2024
  43. 09/13 reftable/generic: move seeking of records into the iteratorPatrick Steinhardt, May 13, 2024
  44. 10/13 reftable/generic: adapt interface to allow reuse of iteratorsPatrick Steinhardt, May 13, 2024
  45. 11/13 reftable/reader: adapt interface to allow reuse of iteratorsPatrick Steinhardt, May 13, 2024
  46. 12/13 reftable/stack: provide convenience functions to create iteratorsPatrick Steinhardt, May 13, 2024
  47. 13/13 reftable/merged: adapt interface to allow reuse of iteratorsPatrick Steinhardt, May 13, 2024
  48. Justin ToblerMay 15, 2024
  49. Karthik NayakMay 21, 2024
  50. Patrick SteinhardtMay 22, 2024

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