Blocking Queries in a Master Index (Repository)

When the master index application evaluates possible matches of records sent to the master index application from external systems and from the EDM, the index performs a set of predefined SQL queries to retrieve a subset of possible matches. These queries are known as blocking queries. The matching algorithm processes the input record against the profiles retrieved from the blocking query (known as the candidate pool) and assigns them matching probability weights.

In the Candidate Select file, you define the criteria and conditions for querying the database to retrieve the subset of possible matches to the incoming record, including Oracle hints and SQL Server OPTION hints. You can define multiple queries, known as blocks, for each blocking query, and the master index application performs each of these queries in turn until sufficient records are retrieved (called a match pass). Using the default Query Builder, a block is only processed if the search criteria include all of the fields defined for that block. Each field in a block is joined by an AND operator in the WHERE clause, and each block is joined by a UNION operator. This type of search can also be used as a phonetic search in the EDM.

The blocking queries you define here are referenced in the Threshold file, which specifies which one of the defined blocking queries to use for match processing. They might also be referenced in the Enterprise Data Manager file if a blocking query is used for phonetic searches from the EDM. To enable extensive searching (that is, searching against additional tables, such as an alias table for a person index), you must add the fields from that table to the blocking query.