rocksdb/table
Mike Kolupaev 8bf555f487 Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs
Summary:
Before this PR, Iterator/InternalIterator may simultaneously have non-ok status() and Valid() = true. That state means that the last operation failed, but the iterator is nevertheless positioned on some unspecified record. Likely intended uses of that are:
 * If some sst files are corrupted, a normal iterator can be used to read the data from files that are not corrupted.
 * When using read_tier = kBlockCacheTier, read the data that's in block cache, skipping over the data that is not.

However, this behavior wasn't documented well (and until recently the wiki on github had misleading incorrect information). In the code there's a lot of confusion about the relationship between status() and Valid(), and about whether Seek()/SeekToLast()/etc reset the status or not. There were a number of bugs caused by this confusion, both inside rocksdb and in the code that uses rocksdb (including ours).

This PR changes the convention to:
 * If status() is not ok, Valid() always returns false.
 * Any seek operation resets status. (Before the PR, it depended on iterator type and on particular error.)

This does sacrifice the two use cases listed above, but siying said it's ok.

Overview of the changes:
 * A commit that adds missing status checks in MergingIterator. This fixes a bug that actually affects us, and we need it fixed. `DBIteratorTest.NonBlockingIterationBugRepro` explains the scenario.
 * Changes to lots of iterator types to make all of them conform to the new convention. Some bug fixes along the way. By far the biggest changes are in DBIter, which is a big messy piece of code; I tried to make it less big and messy but mostly failed.
 * A stress-test for DBIter, to gain some confidence that I didn't break it. It does a few million random operations on the iterator, while occasionally modifying the underlying data (like ForwardIterator does) and occasionally returning non-ok status from internal iterator.

To find the iterator types that needed changes I searched for "public .*Iterator" in the code. Here's an overview of all 27 iterator types:

Iterators that didn't need changes:
 * status() is always ok(), or Valid() is always false: MemTableIterator, ModelIter, TestIterator, KVIter (2 classes with this name anonymous namespaces), LoggingForwardVectorIterator, VectorIterator, MockTableIterator, EmptyIterator, EmptyInternalIterator.
 * Thin wrappers that always pass through Valid() and status(): ArenaWrappedDBIter, TtlIterator, InternalIteratorFromIterator.

Iterators with changes (see inline comments for details):
 * DBIter - an overhaul:
    - It used to silently skip corrupted keys (`FindParseableKey()`), which seems dangerous. This PR makes it just stop immediately after encountering a corrupted key, just like it would for other kinds of corruption. Let me know if there was actually some deeper meaning in this behavior and I should put it back.
    - It had a few code paths silently discarding subiterator's status. The stress test caught a few.
    - The backwards iteration code path was expecting the internal iterator's set of keys to be immutable. It's probably always true in practice at the moment, since ForwardIterator doesn't support backwards iteration, but this PR fixes it anyway. See added DBIteratorTest.ReverseToForwardBug for an example.
    - Some parts of backwards iteration code path even did things like `assert(iter_->Valid())` after a seek, which is never a safe assumption.
    - It used to not reset status on seek for some types of errors.
    - Some simplifications and better comments.
    - Some things got more complicated from the added error handling. I'm open to ideas for how to make it nicer.
 * MergingIterator - check status after every operation on every subiterator, and in some places assert that valid subiterators have ok status.
 * ForwardIterator - changed to the new convention, also slightly simplified.
 * ForwardLevelIterator - fixed some bugs and simplified.
 * LevelIterator - simplified.
 * TwoLevelIterator - changed to the new convention. Also fixed a bug that would make SeekForPrev() sometimes silently ignore errors from first_level_iter_.
 * BlockBasedTableIterator - minor changes.
 * BlockIter - replaced `SetStatus()` with `Invalidate()` to make sure non-ok BlockIter is always invalid.
 * PlainTableIterator - some seeks used to not reset status.
 * CuckooTableIterator - tiny code cleanup.
 * ManagedIterator - fixed some bugs.
 * BaseDeltaIterator - changed to the new convention and fixed a bug.
 * BlobDBIterator - seeks used to not reset status.
 * KeyConvertingIterator - some small change.
Closes https://github.com/facebook/rocksdb/pull/3810

Differential Revision: D7888019

Pulled By: al13n321

fbshipit-source-id: 4aaf6d3421c545d16722a815b2fa2e7912bc851d
2018-05-17 02:56:56 -07:00
..
adaptive_table_factory.cc Comment out unused variables 2018-03-05 13:13:41 -08:00
adaptive_table_factory.h Comment out unused variables 2018-03-05 13:13:41 -08:00
block_based_filter_block_test.cc Ignore empty filter block when data block is empty 2018-03-21 23:13:05 -07:00
block_based_filter_block.cc Fix a leak in FilterBlockBuilder when adding prefix 2018-03-27 15:13:56 -07:00
block_based_filter_block.h Ignore empty filter block when data block is empty 2018-03-21 23:13:05 -07:00
block_based_table_builder.cc Align SST file data blocks to avoid spanning multiple pages 2018-03-26 20:26:10 -07:00
block_based_table_builder.h Align SST file data blocks to avoid spanning multiple pages 2018-03-26 20:26:10 -07:00
block_based_table_factory.cc comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
block_based_table_factory.h Align SST file data blocks to avoid spanning multiple pages 2018-03-26 20:26:10 -07:00
block_based_table_reader.cc Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
block_based_table_reader.h Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
block_builder.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
block_builder.h Change RocksDB License 2017-07-15 16:11:23 -07:00
block_fetcher.cc Imporve perf of random read and insert compare by suggesting inlining to the compiler 2018-03-23 13:26:55 -07:00
block_fetcher.h Fix BlockFetcher ASAN error 2017-12-12 12:12:38 -08:00
block_prefix_index.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
block_prefix_index.h Change RocksDB License 2017-07-15 16:11:23 -07:00
block_test.cc Comment out unused variables 2018-03-05 13:13:41 -08:00
block.cc Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
block.h Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
bloom_block.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
bloom_block.h Change RocksDB License 2017-07-15 16:11:23 -07:00
cleanable_test.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
cuckoo_table_builder_test.cc fix memory leak in two_level_iterator 2018-04-15 17:26:26 -07:00
cuckoo_table_builder.cc Enable MSVC W4 with a few exceptions. Fix warnings and bugs 2017-10-19 10:57:12 -07:00
cuckoo_table_builder.h Change RocksDB License 2017-07-15 16:11:23 -07:00
cuckoo_table_factory.cc Comment out unused variables 2018-03-05 13:13:41 -08:00
cuckoo_table_factory.h comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
cuckoo_table_reader_test.cc fix memory leak in two_level_iterator 2018-04-15 17:26:26 -07:00
cuckoo_table_reader.cc Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
cuckoo_table_reader.h Comment out unused variables 2018-03-05 13:13:41 -08:00
filter_block.h Ignore empty filter block when data block is empty 2018-03-21 23:13:05 -07:00
flush_block_policy.cc Align SST file data blocks to avoid spanning multiple pages 2018-03-26 20:26:10 -07:00
format.cc Several small "fixes" 2018-02-15 16:57:37 -08:00
format.h comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
full_filter_bits_builder.h Skip duplicate bloom keys when whole_key and prefix are mixed 2018-04-24 10:58:16 -07:00
full_filter_block_test.cc Fix the bloom filter skipping empty prefixes 2018-04-26 13:28:31 -07:00
full_filter_block.cc Fix the bloom filter skipping empty prefixes 2018-04-26 13:28:31 -07:00
full_filter_block.h Fix the bloom filter skipping empty prefixes 2018-04-26 13:28:31 -07:00
get_context.cc comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
get_context.h Stats for false positive rate of full filtesr 2018-04-05 15:58:48 -07:00
index_builder.cc Enable MSVC W4 with a few exceptions. Fix warnings and bugs 2017-10-19 10:57:12 -07:00
index_builder.h Comment out unused variables 2018-03-05 13:13:41 -08:00
internal_iterator.h Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
iter_heap.h Make InternalKeyComparator final and directly use it in merging iterator 2017-09-11 12:04:21 -07:00
iterator_wrapper.h Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
iterator.cc Comment out unused variables 2018-03-05 13:13:41 -08:00
merger_test.cc Make InternalKeyComparator final and directly use it in merging iterator 2017-09-11 12:04:21 -07:00
merging_iterator.cc Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
merging_iterator.h fix DBImpl::NewInternalIterator super-version leak on failure 2017-10-11 14:57:43 -07:00
meta_blocks.cc Refactor ReadBlockContents() 2017-12-11 15:27:32 -08:00
meta_blocks.h Support prefetch last 512KB with direct I/O in block based file reader 2017-08-11 12:16:45 -07:00
mock_table.cc Stats for false positive rate of full filtesr 2018-04-05 15:58:48 -07:00
mock_table.h Comment out unused variables 2018-03-05 13:13:41 -08:00
partitioned_filter_block_test.cc Reduce heavy hitter for Get operation 2017-12-12 21:11:33 -08:00
partitioned_filter_block.cc comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
partitioned_filter_block.h Fix the memory leak with pinned partitioned filters 2018-04-09 16:28:19 -07:00
persistent_cache_helper.cc comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
persistent_cache_helper.h Change RocksDB License 2017-07-15 16:11:23 -07:00
persistent_cache_options.h Change RocksDB License 2017-07-15 16:11:23 -07:00
plain_table_builder.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
plain_table_builder.h Change RocksDB License 2017-07-15 16:11:23 -07:00
plain_table_factory.cc Comment out unused variables 2018-03-05 13:13:41 -08:00
plain_table_factory.h Comment out unused variables 2018-03-05 13:13:41 -08:00
plain_table_index.cc Change RocksDB License 2017-07-15 16:11:23 -07:00
plain_table_index.h table: Fix coverity issues 2017-12-07 11:57:36 -08:00
plain_table_key_coding.cc Comment out unused variables 2018-03-05 13:13:41 -08:00
plain_table_key_coding.h Change RocksDB License 2017-07-15 16:11:23 -07:00
plain_table_reader.cc Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
plain_table_reader.h remove unnecessary internal_comparator param in newIterator 2017-07-27 14:30:42 -07:00
scoped_arena_iterator.h Change RocksDB License 2017-07-15 16:11:23 -07:00
sst_file_writer_collectors.h Comment out unused variables 2018-03-05 13:13:41 -08:00
sst_file_writer.cc Fix some typos in comments and docs. 2018-03-08 10:27:25 -08:00
table_builder.h TableProperty::oldest_key_time defaults to 0 2017-10-27 15:00:05 -07:00
table_properties_internal.h Eliminate some redundant block reads. 2018-01-10 17:11:58 -08:00
table_properties.cc Eliminate some redundant block reads. 2018-01-10 17:11:58 -08:00
table_reader_bench.cc comment unused parameters to turn on -Wunused-parameter flag 2018-04-12 17:59:16 -07:00
table_reader.h Comment out unused variables 2018-03-05 13:13:41 -08:00
table_test.cc Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
two_level_iterator.cc Change and clarify the relationship between Valid(), status() and Seek*() for all iterators. Also fix some bugs 2018-05-17 02:56:56 -07:00
two_level_iterator.h fix memory leak in two_level_iterator 2018-04-15 17:26:26 -07:00