局部敏感散列可以用于动态数据吗?例如,假设我首先对1,000,000个文档使用LSH,并将结果存储在索引中,然后我想将另一个文档添加到创建的索引中。我可以使用LSH吗?
是。
由于lsh使用多个哈希来生成多个签名,那么这些签名将被绑定来生成索引。如果存储随机散列函数和分组过程,则可以重用它来为新插入生成索引。因此,对于每个新的插入,您将有相应的索引
是的,你可以这样做。您只需要计算添加的文档与其他文档的Jaccard相似度,并将其添加到索引中。
TABLE Documents (
ID INT IDENTITY(1,1) PRIMARY KEY NOT NULL,
MinHashes BINARY(512), -- serialized Min Hash results
Name NVARCHAR(255) UNIQUE NOT NULL,
Content VARBINARY(MAX)
)
TABLE SimilarDocumentIndex (
DocumentAID INT REFERENCES Documents(ID),
DocumentBID INT REFERENCES Documents(ID),
Similarity FLOAT, -- Jaccard Similarity 0.0...1.0
PRIMARY KEY CLUSTERED (DocumentAID, DocumentBID)
)
--
-- Find similar documents
--
SELECT TOP 20 DISTINCT DocumentID
FROM (SELECT
FROM SimilarDocumentIndex
WHERE DocumentAID = @DocumentID
ORDER BY Similarity DESC
--
-- Compare two documents
--
SELECT Similarity
FROM SimilarDocumentIndex
WHERE DocumentAID = @DocumentAID AND DocumentBID = @DocumentBID
--
-- Adding a new document
--
SET @MinHashes = dbo.CalcMinHashes(@content)
INSERT INTO Document
VALUES(@MinHashes, @name, @content)
SET @DocumentID = SCOPE_IDENTITY()
INSERT INTO SimilarDocumentIndex
SELECT @DocumentID, ID, dbo.JaccardSimilarity(@MinHashes, MinHashes)
FROM Documents
WHERE ID <> @DocumentID
INSERT INTO SimilarDocumentIndex
SELECT DocumentBID, @DocumentID, Similarity
FROM SimilarDocumentIndex
WHERE DocumentAID = @DocumentID