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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
package org.rocksdb;
import java.util.List;
/**
* Advanced Column Family Options which are not
* mutable (i.e. present in {@link AdvancedMutableColumnFamilyOptionsInterface})
*
* Taken from include/rocksdb/advanced_options.h
*/
public interface AdvancedColumnFamilyOptionsInterface<
T extends AdvancedColumnFamilyOptionsInterface & ColumnFamilyOptionsInterface> {
/**
* The minimum number of write buffers that will be merged together
* before writing to storage. If set to 1, then
* all write buffers are flushed to L0 as individual files and this increases
* read amplification because a get request has to check in all of these
* files. Also, an in-memory merge may result in writing lesser
* data to storage if there are duplicate records in each of these
* individual write buffers. Default: 1
*
* @param minWriteBufferNumberToMerge the minimum number of write buffers
* that will be merged together.
* @return the reference to the current options.
*/
T setMinWriteBufferNumberToMerge(
int minWriteBufferNumberToMerge);
/**
* The minimum number of write buffers that will be merged together
* before writing to storage. If set to 1, then
* all write buffers are flushed to L0 as individual files and this increases
* read amplification because a get request has to check in all of these
* files. Also, an in-memory merge may result in writing lesser
* data to storage if there are duplicate records in each of these
* individual write buffers. Default: 1
*
* @return the minimum number of write buffers that will be merged together.
*/
int minWriteBufferNumberToMerge();
/**
* The total maximum number of write buffers to maintain in memory including
* copies of buffers that have already been flushed. Unlike
* {@link AdvancedMutableColumnFamilyOptionsInterface#maxWriteBufferNumber()},
* this parameter does not affect flushing.
* This controls the minimum amount of write history that will be available
* in memory for conflict checking when Transactions are used.
*
* When using an OptimisticTransactionDB:
* If this value is too low, some transactions may fail at commit time due
* to not being able to determine whether there were any write conflicts.
*
* When using a TransactionDB:
* If Transaction::SetSnapshot is used, TransactionDB will read either
* in-memory write buffers or SST files to do write-conflict checking.
* Increasing this value can reduce the number of reads to SST files
* done for conflict detection.
*
* Setting this value to 0 will cause write buffers to be freed immediately
* after they are flushed.
* If this value is set to -1,
* {@link AdvancedMutableColumnFamilyOptionsInterface#maxWriteBufferNumber()}
* will be used.
*
* Default:
* If using a TransactionDB/OptimisticTransactionDB, the default value will
* be set to the value of
* {@link AdvancedMutableColumnFamilyOptionsInterface#maxWriteBufferNumber()}
* if it is not explicitly set by the user. Otherwise, the default is 0.
*
* @param maxWriteBufferNumberToMaintain The maximum number of write
* buffers to maintain
*
* @return the reference to the current options.
*/
T setMaxWriteBufferNumberToMaintain(
int maxWriteBufferNumberToMaintain);
/**
* The total maximum number of write buffers to maintain in memory including
* copies of buffers that have already been flushed.
*
* @return maxWriteBufferNumberToMaintain The maximum number of write buffers
* to maintain
*/
int maxWriteBufferNumberToMaintain();
/**
* Allows thread-safe inplace updates.
* If inplace_callback function is not set,
* Put(key, new_value) will update inplace the existing_value iff
* * key exists in current memtable
* * new sizeof(new_value) ≤ sizeof(existing_value)
* * existing_value for that key is a put i.e. kTypeValue
* If inplace_callback function is set, check doc for inplace_callback.
* Default: false.
*
* @param inplaceUpdateSupport true if thread-safe inplace updates
* are allowed.
* @return the reference to the current options.
*/
T setInplaceUpdateSupport(
boolean inplaceUpdateSupport);
/**
* Allows thread-safe inplace updates.
* If inplace_callback function is not set,
* Put(key, new_value) will update inplace the existing_value iff
* * key exists in current memtable
* * new sizeof(new_value) ≤ sizeof(existing_value)
* * existing_value for that key is a put i.e. kTypeValue
* If inplace_callback function is set, check doc for inplace_callback.
* Default: false.
*
* @return true if thread-safe inplace updates are allowed.
*/
boolean inplaceUpdateSupport();
/**
* Control locality of bloom filter probes to improve cache miss rate.
* This option only applies to memtable prefix bloom and plaintable
* prefix bloom. It essentially limits the max number of cache lines each
* bloom filter check can touch.
* This optimization is turned off when set to 0. The number should never
* be greater than number of probes. This option can boost performance
* for in-memory workload but should use with care since it can cause
* higher false positive rate.
* Default: 0
*
* @param bloomLocality the level of locality of bloom-filter probes.
* @return the reference to the current options.
*/
T setBloomLocality(int bloomLocality);
/**
* Control locality of bloom filter probes to improve cache miss rate.
* This option only applies to memtable prefix bloom and plaintable
* prefix bloom. It essentially limits the max number of cache lines each
* bloom filter check can touch.
* This optimization is turned off when set to 0. The number should never
* be greater than number of probes. This option can boost performance
* for in-memory workload but should use with care since it can cause
* higher false positive rate.
* Default: 0
*
* @return the level of locality of bloom-filter probes.
* @see #setBloomLocality(int)
*/
int bloomLocality();
/**
*
Different levels can have different compression
* policies. There are cases where most lower levels
* would like to use quick compression algorithms while
* the higher levels (which have more data) use
* compression algorithms that have better compression
* but could be slower. This array, if non-empty, should
* have an entry for each level of the database;
* these override the value specified in the previous
* field 'compression'.
*
* NOTICE
* If {@code level_compaction_dynamic_level_bytes=true},
* {@code compression_per_level[0]} still determines {@code L0},
* but other elements of the array are based on base level
* (the level {@code L0} files are merged to), and may not
* match the level users see from info log for metadata.
*
* If {@code L0} files are merged to {@code level - n},
* then, for {@code i>0}, {@code compression_per_level[i]}
* determines compaction type for level {@code n+i-1}.
*
* Example
* For example, if we have 5 levels, and we determine to
* merge {@code L0} data to {@code L4} (which means {@code L1..L3}
* will be empty), then the new files go to {@code L4} uses
* compression type {@code compression_per_level[1]}.
*
* If now {@code L0} is merged to {@code L2}. Data goes to
* {@code L2} will be compressed according to
* {@code compression_per_level[1]}, {@code L3} using
* {@code compression_per_level[2]}and {@code L4} using
* {@code compression_per_level[3]}. Compaction for each
* level can change when data grows.
*
* Default: empty
*
* @param compressionLevels list of
* {@link org.rocksdb.CompressionType} instances.
*
* @return the reference to the current options.
*/
T setCompressionPerLevel(
List compressionLevels);
/**
* Return the currently set {@link org.rocksdb.CompressionType}
* per instances.
*
* See: {@link #setCompressionPerLevel(java.util.List)}
*
* @return list of {@link org.rocksdb.CompressionType}
* instances.
*/
List compressionPerLevel();
/**
* Set the number of levels for this database
* If level-styled compaction is used, then this number determines
* the total number of levels.
*
* @param numLevels the number of levels.
* @return the reference to the current options.
*/
T setNumLevels(int numLevels);
/**
* If level-styled compaction is used, then this number determines
* the total number of levels.
*
* @return the number of levels.
*/
int numLevels();
/**
* If {@code true}, RocksDB will pick target size of each level
* dynamically. We will pick a base level b >= 1. L0 will be
* directly merged into level b, instead of always into level 1.
* Level 1 to b-1 need to be empty. We try to pick b and its target
* size so that
*
*
* - target size is in the range of
* (max_bytes_for_level_base / max_bytes_for_level_multiplier,
* max_bytes_for_level_base]
* - target size of the last level (level num_levels-1) equals to extra size
* of the level.
*
*
* At the same time max_bytes_for_level_multiplier and
* max_bytes_for_level_multiplier_additional are still satisfied.
*
* With this option on, from an empty DB, we make last level the base
* level, which means merging L0 data into the last level, until it exceeds
* max_bytes_for_level_base. And then we make the second last level to be
* base level, to start to merge L0 data to second last level, with its
* target size to be {@code 1/max_bytes_for_level_multiplier} of the last
* levels extra size. After the data accumulates more so that we need to
* move the base level to the third last one, and so on.
*
* Example
*
* For example, assume {@code max_bytes_for_level_multiplier=10},
* {@code num_levels=6}, and {@code max_bytes_for_level_base=10MB}.
*
* Target sizes of level 1 to 5 starts with:
* {@code [- - - - 10MB]}
* with base level is level. Target sizes of level 1 to 4 are not applicable
* because they will not be used.
* Until the size of Level 5 grows to more than 10MB, say 11MB, we make
* base target to level 4 and now the targets looks like:
* {@code [- - - 1.1MB 11MB]}
* While data are accumulated, size targets are tuned based on actual data
* of level 5. When level 5 has 50MB of data, the target is like:
* {@code [- - - 5MB 50MB]}
* Until level 5's actual size is more than 100MB, say 101MB. Now if we
* keep level 4 to be the base level, its target size needs to be 10.1MB,
* which doesn't satisfy the target size range. So now we make level 3
* the target size and the target sizes of the levels look like:
* {@code [- - 1.01MB 10.1MB 101MB]}
* In the same way, while level 5 further grows, all levels' targets grow,
* like
* {@code [- - 5MB 50MB 500MB]}
* Until level 5 exceeds 1000MB and becomes 1001MB, we make level 2 the
* base level and make levels' target sizes like this:
* {@code [- 1.001MB 10.01MB 100.1MB 1001MB]}
* and go on...
*
* By doing it, we give {@code max_bytes_for_level_multiplier} a priority
* against {@code max_bytes_for_level_base}, for a more predictable LSM tree
* shape. It is useful to limit worse case space amplification.
*
* {@code max_bytes_for_level_multiplier_additional} is ignored with
* this flag on.
*
* Turning this feature on or off for an existing DB can cause unexpected
* LSM tree structure so it's not recommended.
*
* Caution: this option is experimental
*
* Default: false
*
* @param enableLevelCompactionDynamicLevelBytes boolean value indicating
* if {@code LevelCompactionDynamicLevelBytes} shall be enabled.
* @return the reference to the current options.
*/
@Experimental("Turning this feature on or off for an existing DB can cause" +
" unexpected LSM tree structure so it's not recommended")
T setLevelCompactionDynamicLevelBytes(
boolean enableLevelCompactionDynamicLevelBytes);
/**
* Return if {@code LevelCompactionDynamicLevelBytes} is enabled.
*
*
* For further information see
* {@link #setLevelCompactionDynamicLevelBytes(boolean)}
*
* @return boolean value indicating if
* {@code levelCompactionDynamicLevelBytes} is enabled.
*/
@Experimental("Caution: this option is experimental")
boolean levelCompactionDynamicLevelBytes();
/**
* Maximum size of each compaction (not guarantee)
*
* @param maxCompactionBytes the compaction size limit
* @return the reference to the current options.
*/
T setMaxCompactionBytes(
long maxCompactionBytes);
/**
* Control maximum size of each compaction (not guaranteed)
*
* @return compaction size threshold
*/
long maxCompactionBytes();
/**
* Set compaction style for DB.
*
* Default: LEVEL.
*
* @param compactionStyle Compaction style.
* @return the reference to the current options.
*/
ColumnFamilyOptionsInterface setCompactionStyle(CompactionStyle compactionStyle);
/**
* Compaction style for DB.
*
* @return Compaction style.
*/
CompactionStyle compactionStyle();
/**
* If level {@link #compactionStyle()} == {@link CompactionStyle#LEVEL},
* for each level, which files are prioritized to be picked to compact.
*
* Default: {@link CompactionPriority#ByCompensatedSize}
*
* @param compactionPriority The compaction priority
*
* @return the reference to the current options.
*/
T setCompactionPriority(
CompactionPriority compactionPriority);
/**
* Get the Compaction priority if level compaction
* is used for all levels
*
* @return The compaction priority
*/
CompactionPriority compactionPriority();
/**
* Set the options needed to support Universal Style compactions
*
* @param compactionOptionsUniversal The Universal Style compaction options
*
* @return the reference to the current options.
*/
T setCompactionOptionsUniversal(
CompactionOptionsUniversal compactionOptionsUniversal);
/**
* The options needed to support Universal Style compactions
*
* @return The Universal Style compaction options
*/
CompactionOptionsUniversal compactionOptionsUniversal();
/**
* The options for FIFO compaction style
*
* @param compactionOptionsFIFO The FIFO compaction options
*
* @return the reference to the current options.
*/
T setCompactionOptionsFIFO(
CompactionOptionsFIFO compactionOptionsFIFO);
/**
* The options for FIFO compaction style
*
* @return The FIFO compaction options
*/
CompactionOptionsFIFO compactionOptionsFIFO();
/**
*
This flag specifies that the implementation should optimize the filters
* mainly for cases where keys are found rather than also optimize for keys
* missed. This would be used in cases where the application knows that
* there are very few misses or the performance in the case of misses is not
* important.
*
* For now, this flag allows us to not store filters for the last level i.e
* the largest level which contains data of the LSM store. For keys which
* are hits, the filters in this level are not useful because we will search
* for the data anyway.
*
* NOTE: the filters in other levels are still useful
* even for key hit because they tell us whether to look in that level or go
* to the higher level.
*
* Default: false
*
* @param optimizeFiltersForHits boolean value indicating if this flag is set.
* @return the reference to the current options.
*/
T setOptimizeFiltersForHits(
boolean optimizeFiltersForHits);
/**
*
Returns the current state of the {@code optimize_filters_for_hits}
* setting.
*
* @return boolean value indicating if the flag
* {@code optimize_filters_for_hits} was set.
*/
boolean optimizeFiltersForHits();
/**
* By default, RocksDB runs consistency checks on the LSM every time the LSM
* changes (Flush, Compaction, AddFile). Use this option if you need to
* disable them.
*
* Default: true
*
* @param forceConsistencyChecks false to disable consistency checks
*
* @return the reference to the current options.
*/
T setForceConsistencyChecks(
boolean forceConsistencyChecks);
/**
* By default, RocksDB runs consistency checks on the LSM every time the LSM
* changes (Flush, Compaction, AddFile).
*
* @return true if consistency checks are enforced
*/
boolean forceConsistencyChecks();
}