org.neo4j.storageengine.api

Interface StorageStatement

All Superinterfaces:

AutoCloseable

public interface StorageStatement
extends AutoCloseable

A statement for accessing data from a StoreReadLayer. Most data about the entities of a graph are accessed through this statement interface as opposed to through the StoreReadLayer directly. One of the main reasons is that the access methods returns objects, like cursors which are valuable to reuse over a reasonably large window to reduce garbage churn in general.

A StorageStatement must be acquired before use. After use the statement should be released. After released the statement can be acquired again. Creating and closing StorageStatement and there's also benefits keeping these statements opened during a longer period of time, with the assumption that it's still one thread at a time using each. With that in mind these statements should not be opened and closed for each operation, perhaps not even for each transaction.

All cursors provided by this statement are views over data in the store. They do not interact with transaction state.

Method Summary

Modifier and Type	Method and Description
void	acquire() Acquires this statement so that it can be used, should later be released.
org.neo4j.cursor.Cursor<NodeItem>	acquireSingleNodeCursor(long nodeId) Acquires Cursor capable of serving NodeItem for selected nodes.
org.neo4j.cursor.Cursor<RelationshipItem>	acquireSingleRelationshipCursor(long relationshipId) Acquires Cursor capable of serving RelationshipItem for selected relationships.
void	close() Closes this statement so that it can no longer be used nor acquired.
IndexReader	getFreshIndexReader(org.neo4j.kernel.api.schema.IndexDescriptor index) Returns an IndexReader for searching entity ids given property values.
IndexReader	getIndexReader(org.neo4j.kernel.api.schema.IndexDescriptor index) Returns an IndexReader for searching entity ids given property values.
LabelScanReader	getLabelScanReader()
org.neo4j.cursor.Cursor<RelationshipItem>	relationshipsGetAllCursor() - * Acquires Cursor capable of serving RelationshipItem for selected - * relationships.
void	release() Releases this statement so that it can later be acquired again.

Method Detail

acquire

void acquire()

Acquires this statement so that it can be used, should later be released. Since a StorageStatement can be reused after released, this call should do initialization/clearing of state whereas data structures can be kept between uses.

release

void release()

Releases this statement so that it can later be acquired again.

close

void close()

Closes this statement so that it can no longer be used nor acquired.

Specified by:

close in interface AutoCloseable

acquireSingleNodeCursor

org.neo4j.cursor.Cursor<NodeItem> acquireSingleNodeCursor(long nodeId)

Acquires Cursor capable of serving NodeItem for selected nodes. No node is selected when this method returns, a call to Cursor.next() will have to be made to place the cursor over the first item and then more calls to move the cursor through the selection.

Parameters:

nodeId - id of node to get cursor for.

Returns:

a Cursor over NodeItem for the given nodeId.

acquireSingleRelationshipCursor

org.neo4j.cursor.Cursor<RelationshipItem> acquireSingleRelationshipCursor(long relationshipId)

Acquires Cursor capable of serving RelationshipItem for selected relationships. No relationship is selected when this method returns, a call to Cursor.next() will have to be made to place the cursor over the first item and then more calls to move the cursor through the selection.

Parameters:

relationshipId - id of relationship to get cursor for.

Returns:

a Cursor over RelationshipItem for the given relationshipId.

relationshipsGetAllCursor

org.neo4j.cursor.Cursor<RelationshipItem> relationshipsGetAllCursor()

- * Acquires Cursor capable of serving RelationshipItem for selected - * relationships. No relationship is selected when this method returns, a call to Cursor.next() - * will have to be made to place the cursor over the first item and then more calls to move the cursor - * through the selection. - * - * @return a Cursor over all stored relationships. -

getLabelScanReader

LabelScanReader getLabelScanReader()

Returns:

LabelScanReader capable of reading nodes for specific label ids.

getIndexReader

IndexReader getIndexReader(org.neo4j.kernel.api.schema.IndexDescriptor index)
                    throws org.neo4j.kernel.api.exceptions.index.IndexNotFoundKernelException

Returns an IndexReader for searching entity ids given property values. One reader is allocated and kept per index throughout the life of a statement, making the returned reader repeatable-read isolation.

NOTE: Reader returned from this method should not be closed. All such readers will be closed during close() of the current statement.

Parameters:

index - IndexDescriptor to get reader for.

Returns:

IndexReader capable of searching entity ids given property values.

Throws:

org.neo4j.kernel.api.exceptions.index.IndexNotFoundKernelException - if no such index exists.

getFreshIndexReader

IndexReader getFreshIndexReader(org.neo4j.kernel.api.schema.IndexDescriptor index)
                         throws org.neo4j.kernel.api.exceptions.index.IndexNotFoundKernelException

Returns an IndexReader for searching entity ids given property values. A new reader is allocated every call to this method, which means that newly committed data since the last call to this method will be visible in the returned reader.

NOTE: It is caller's responsibility to close the returned reader.

Parameters:

index - IndexDescriptor to get reader for.

Returns:

IndexReader capable of searching entity ids given property values.

Throws:

org.neo4j.kernel.api.exceptions.index.IndexNotFoundKernelException - if no such index exists.