From 5340484266df3e07544b6f4aa82f30dbbdc39af2 Mon Sep 17 00:00:00 2001 From: fyrz Date: Fri, 26 Sep 2014 10:35:12 +0200 Subject: [PATCH] Built-in comparator(s) in RocksJava Extended Built-in comparators with ReverseBytewiseComparator. Reverse key handling is under certain conditions essential. E.g. while using timestamp versioned data. As native-comparators were not available using JAVA-API. Both built-in comparators were exposed via JNI to be set upon database creation time. --- include/rocksdb/comparator.h | 4 ++++ java/org/rocksdb/Options.java | 23 +++++++++++++++++++++++ java/rocksjni/options.cc | 18 ++++++++++++++++++ util/comparator.cc | 23 ++++++++++++++++++++++- 4 files changed, 67 insertions(+), 1 deletion(-) diff --git a/include/rocksdb/comparator.h b/include/rocksdb/comparator.h index f3a8499a8..8e7366752 100644 --- a/include/rocksdb/comparator.h +++ b/include/rocksdb/comparator.h @@ -62,6 +62,10 @@ class Comparator { // must not be deleted. extern const Comparator* BytewiseComparator(); +// Return a builtin comparator that uses reverse lexicographic byte-wise +// ordering. +extern const Comparator* ReverseBytewiseComparator(); + } // namespace rocksdb #endif // STORAGE_ROCKSDB_INCLUDE_COMPARATOR_H_ diff --git a/java/org/rocksdb/Options.java b/java/org/rocksdb/Options.java index 8446136f8..7ccc74834 100644 --- a/java/org/rocksdb/Options.java +++ b/java/org/rocksdb/Options.java @@ -18,6 +18,14 @@ public class Options extends RocksObject { } static final long DEFAULT_CACHE_SIZE = 8 << 20; static final int DEFAULT_NUM_SHARD_BITS = -1; + + /** + * Builtin RocksDB comparators + */ + public enum BuiltinComparator { + BYTEWISE_COMPARATOR, REVERSE_BYTEWISE_COMPARATOR; + } + /** * Construct options for opening a RocksDB. * @@ -78,6 +86,21 @@ public class Options extends RocksObject { return createIfMissing(nativeHandle_); } + /** + * Set BuiltinComparator to be used with RocksDB. + * + * Note: Comparator can be set once upon database creation. + * + * Default: BytewiseComparator. + * @param builtinComparator a BuiltinComparator type. + */ + public void setBuiltinComparator(BuiltinComparator builtinComparator) { + assert(isInitialized()); + setBuiltinComparator(nativeHandle_, builtinComparator.ordinal()); + } + + private native void setBuiltinComparator(long handle, int builtinComparator); + /** * Amount of data to build up in memory (backed by an unsorted log * on disk) before converting to a sorted on-disk file. diff --git a/java/rocksjni/options.cc b/java/rocksjni/options.cc index 2dc2ffdc8..50416ef81 100644 --- a/java/rocksjni/options.cc +++ b/java/rocksjni/options.cc @@ -22,6 +22,7 @@ #include "rocksdb/table.h" #include "rocksdb/slice_transform.h" #include "rocksdb/rate_limiter.h" +#include "rocksdb/comparator.h" /* * Class: org_rocksdb_Options @@ -63,6 +64,23 @@ jboolean Java_org_rocksdb_Options_createIfMissing( return reinterpret_cast(jhandle)->create_if_missing; } +/* + * Class: org_rocksdb_Options + * Method: useReverseBytewiseComparator + * Signature: (JI)V + */ +void Java_org_rocksdb_Options_setBuiltinComparator( + JNIEnv* env, jobject jobj, jlong jhandle, jint builtinComparator) { + switch (builtinComparator){ + case 1: + reinterpret_cast(jhandle)->comparator = rocksdb::ReverseBytewiseComparator(); + break; + default: + reinterpret_cast(jhandle)->comparator = rocksdb::BytewiseComparator(); + break; + } +} + /* * Class: org_rocksdb_Options * Method: setWriteBufferSize diff --git a/util/comparator.cc b/util/comparator.cc index adeacac0a..d77d43117 100644 --- a/util/comparator.cc +++ b/util/comparator.cc @@ -69,13 +69,29 @@ class BytewiseComparatorImpl : public Comparator { // *key is a run of 0xffs. Leave it alone. } }; -} // namespace + +class ReverseBytewiseComparatorImpl : public BytewiseComparatorImpl { + public: + ReverseBytewiseComparatorImpl() { } + + virtual const char* Name() const { + return "leveldb.ReverseBytewiseComparator"; + } + + virtual int Compare(const Slice& a, const Slice& b) const { + return -a.compare(b); + } +}; + +}// namespace static port::OnceType once = LEVELDB_ONCE_INIT; static const Comparator* bytewise; +static const Comparator* rbytewise; static void InitModule() { bytewise = new BytewiseComparatorImpl; + rbytewise= new ReverseBytewiseComparatorImpl; } const Comparator* BytewiseComparator() { @@ -83,4 +99,9 @@ const Comparator* BytewiseComparator() { return bytewise; } +const Comparator* ReverseBytewiseComparator() { + port::InitOnce(&once, InitModule); + return rbytewise; +} + } // namespace rocksdb