Summary:
- Takes the burden off developer to close ColumnFamilyHandle instances before closing RocksDB instance
- The change is backward-compatible
----
Previously the pattern for working with Column Families was:
```java
try (final ColumnFamilyOptions cfOpts = new ColumnFamilyOptions().optimizeUniversalStyleCompaction()) {
// list of column family descriptors, first entry must always be default column family
final List<ColumnFamilyDescriptor> cfDescriptors = Arrays.asList(
new ColumnFamilyDescriptor(RocksDB.DEFAULT_COLUMN_FAMILY, cfOpts),
new ColumnFamilyDescriptor("my-first-columnfamily".getBytes(), cfOpts)
);
// a list which will hold the handles for the column families once the db is opened
final List<ColumnFamilyHandle> columnFamilyHandleList =
new ArrayList<>();
try (final DBOptions options = new DBOptions()
.setCreateIfMissing(true)
.setCreateMissingColumnFamilies(true);
final RocksDB db = RocksDB.open(options,
"path/to/do", cfDescriptors,
columnFamilyHandleList)) {
try {
// do something
} finally {
// NOTE user must explicitly frees the column family handles before freeing the db
for (final ColumnFamilyHandle columnFamilyHandle :
columnFamilyHandleList) {
columnFamilyHandle.close();
}
} // frees the column family options
}
} // frees the db and the db options
```
With the changes in this PR, the Java user no longer has to worry about manually closing the Column Families, which allows them to write simpler symmetrical create/free oriented code like this:
```java
try (final ColumnFamilyOptions cfOpts = new ColumnFamilyOptions().optimizeUniversalStyleCompaction()) {
// list of column family descriptors, first entry must always be default column family
final List<ColumnFamilyDescriptor> cfDescriptors = Arrays.asList(
new ColumnFamilyDescriptor(RocksDB.DEFAULT_COLUMN_FAMILY, cfOpts),
new ColumnFamilyDescriptor("my-first-columnfamily".getBytes(), cfOpts)
);
// a list which will hold the handles for the column families once the db is opened
final List<ColumnFamilyHandle> columnFamilyHandleList =
new ArrayList<>();
try (final DBOptions options = new DBOptions()
.setCreateIfMissing(true)
.setCreateMissingColumnFamilies(true);
final RocksDB db = RocksDB.open(options,
"path/to/do", cfDescriptors,
columnFamilyHandleList)) {
// do something
} // frees the column family options, then frees the db and the db options
}
}
```
**NOTE**: The changes in this PR are backwards API compatible, which means existing code using the original approach will also continue to function correctly.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7428
Reviewed By: cheng-chang
Differential Revision: D24063348
Pulled By: jay-zhuang
fbshipit-source-id: 648d7526669923128c863ead94516bf4d50ac658
05fba96927