Class LmdbPageCardinalityEstimator

java.lang.Object

org.eclipse.rdf4j.sail.lmdb.estimate.LmdbPageCardinalityEstimator

All Implemented Interfaces:

Closeable, AutoCloseable

public final class LmdbPageCardinalityEstimator
extends Object
implements Closeable

Transaction-aware facade around the bounded LMDB B+tree range counter.

Callers supply the ID of the already-pinned LMDB read transaction. This class selects the newest valid meta page no newer than that transaction, resolves the requested named database from that same snapshot, and shares decoded pages only among estimates for that snapshot. When the transaction ID or native mapping changes, snapshot(long) installs a fresh cache. This is the boundary that keeps low-level page reads consistent with the logical query view.

The production constructor receives the open LMDB environment so reads can be zero-copy views of LMDB's native map. The file-only constructor intentionally follows the same decoder through positional channel reads and exists for standalone callers and tests. Both paths must produce identical estimates.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	LmdbPageCardinalityEstimator.CardinalityEstimate	Reliability summary for one logical result, possibly combined across databases or physical layouts.
static final record	LmdbPageCardinalityEstimator.Estimate	Estimate and reliability evidence used by TripleStore to decide whether another physical index is worth reading.
static final record	LmdbPageCardinalityEstimator.IndexShape	Precomputed description of how one logical statement-pattern shape maps to one physical LMDB index layout.

Constructor Summary

Constructors

Constructor	Description
LmdbPageCardinalityEstimator(File dataMdbFile)	File-channel fallback constructor, retained for compatibility and standalone tests.
LmdbPageCardinalityEstimator(File dataMdbFile, long env)	Native-map constructor used by TripleStore.

Method Summary

Modifier and Type	Method	Description
static int	bindingMask(long subject, long predicate, long object, long context)
void	close()
static LmdbPageCardinalityEstimator.CardinalityEstimate	combineDatabaseEstimates(LmdbPageCardinalityEstimator.Estimate first, LmdbPageCardinalityEstimator.Estimate second)	Adds reliability evidence for disjoint explicit and inferred databases.
static LmdbPageCardinalityEstimator.CardinalityEstimate	combineIndexEstimates(LmdbPageCardinalityEstimator.CardinalityEstimate first, LmdbPageCardinalityEstimator.CardinalityEstimate second)	Reconciles estimates of the same logical result obtained from different physical index layouts.
void	configureIndexes(List<String> fieldSequences)	Configures the immutable physical statement-index layouts used by this store.
long	estimateEntries(long txnId, String dbName, byte[] minKey, int minKeyLength, byte[] maxKey, int maxKeyLength, GroupMatcher matcher)
long	estimateEntries(long txnId, String dbName, byte[] minKey, int minKeyLength, byte[] maxKey, int maxKeyLength, GroupMatcher matcher, int residualFieldCount)
LmdbPageCardinalityEstimator.Estimate	estimateEntriesWithQuality(long txnId, String dbName, byte[] minKey, int minKeyLength, byte[] maxKey, int maxKeyLength, GroupMatcher matcher, int residualFieldCount)
LmdbPageCardinalityEstimator.IndexShape	indexShape(int index, int bindingMask)
int	primaryIndex(int bindingMask)
int	secondaryIndex(int bindingMask)	Returns -1 when a separate physical layout would not add useful evidence.
long	totalEntries(long txnId, String dbName)

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

LmdbPageCardinalityEstimator

public LmdbPageCardinalityEstimator(File dataMdbFile)
                             throws IOException

File-channel fallback constructor, retained for compatibility and standalone tests.

Throws:

IOException

LmdbPageCardinalityEstimator

public LmdbPageCardinalityEstimator(File dataMdbFile,
 long env)
                             throws IOException

Native-map constructor used by TripleStore. The environment handle lets page reads use LMDB's existing mapping without copying pages through FileChannel.

Throws:

IOException

Method Details

configureIndexes

public void configureIndexes(List<String> fieldSequences)

Configures the immutable physical statement-index layouts used by this store. Selection is precomputed for all 16 logical binding shapes so the optimizer path performs only array lookups.

bindingMask

public static int bindingMask(long subject,
 long predicate,
 long object,
 long context)

primaryIndex

public int primaryIndex(int bindingMask)

secondaryIndex

public int secondaryIndex(int bindingMask)

Returns -1 when a separate physical layout would not add useful evidence.

indexShape

public LmdbPageCardinalityEstimator.IndexShape indexShape(int index,
 int bindingMask)

combineDatabaseEstimates

public static LmdbPageCardinalityEstimator.CardinalityEstimate combineDatabaseEstimates(LmdbPageCardinalityEstimator.Estimate first,
 LmdbPageCardinalityEstimator.Estimate second)

Adds reliability evidence for disjoint explicit and inferred databases.

combineIndexEstimates

public static LmdbPageCardinalityEstimator.CardinalityEstimate combineIndexEstimates(LmdbPageCardinalityEstimator.CardinalityEstimate first,
 LmdbPageCardinalityEstimator.CardinalityEstimate second)

Reconciles estimates of the same logical result obtained from different physical index layouts.

estimateEntries

public long estimateEntries(long txnId,
 String dbName,
 byte[] minKey,
 int minKeyLength,
 byte[] maxKey,
 int maxKeyLength,
 GroupMatcher matcher)
                     throws IOException

Throws:

IOException

estimateEntries

public long estimateEntries(long txnId,
 String dbName,
 byte[] minKey,
 int minKeyLength,
 byte[] maxKey,
 int maxKeyLength,
 GroupMatcher matcher,
 int residualFieldCount)
                     throws IOException

Throws:

IOException

estimateEntriesWithQuality

public LmdbPageCardinalityEstimator.Estimate estimateEntriesWithQuality(long txnId,
 String dbName,
 byte[] minKey,
 int minKeyLength,
 byte[] maxKey,
 int maxKeyLength,
 GroupMatcher matcher,
 int residualFieldCount)
                                                                 throws IOException

Throws:

IOException

totalEntries

public long totalEntries(long txnId,
 String dbName)
                  throws IOException

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException