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Summary: This PR introduces a new implementation of `Iterator` via a new public API called `NewMultiCfIterator()`. The new API takes a vector of column family handles to build a cross-column-family iterator, which internally maintains multiple `DBIter`s as child iterators from a consistent database state. When a key exists in multiple column families, the iterator selects the value (and wide columns) from the first column family containing the key, following the order provided in the `column_families` parameter. Similar to the merging iterator, a min heap is used to iterate across the child iterators. Backward iteration and direction change functionalities will be implemented in future PRs. The comparator used to compare keys across different column families will be derived from the iterator of the first column family specified in `column_families`. This comparator will be checked against the comparators from all other column families that the iterator will traverse. If there's a mismatch with any of the comparators, the initialization of the iterator will fail. Please note that this PR is not enough for users to start using `MultiCfIterator`. The `MultiCfIterator` and related APIs are still marked as "**DO NOT USE - UNDER CONSTRUCTION**". This PR is just the first of many PRs that will follow soon. This PR includes the following: - Introduction and partial implementation of the `MultiCfIterator`, which implements the generic `Iterator` interface. The implementation includes the construction of the iterator, `SeekToFirst()`, `Next()`, `Valid()`, `key()`, `value()`, and `columns()`. - Unit tests to verify iteration across multiple column families in two distinct scenarios: (1) keys are unique across all column families, and (2) the same keys exist in multiple column families. Pull Request resolved: https://github.com/facebook/rocksdb/pull/12153 Reviewed By: pdillinger Differential Revision: D52308697 Pulled By: jaykorean fbshipit-source-id: b03e69f13b40af5a8f0598d0f43a0bec01ef8294 |
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| .. | ||
| db_wide_basic_test.cc | ||
| wide_column_serialization.cc | ||
| wide_column_serialization.h | ||
| wide_column_serialization_test.cc | ||
| wide_columns.cc | ||
| wide_columns_helper.cc | ||
| wide_columns_helper.h | ||
| wide_columns_helper_test.cc | ||