Using Your Own Filters

Go Up to Filtering Blob Data

Unlike the standard InterBase filters that convert between subtype 0 and subtype 1, an external Blob filter is generally part of a library of routines you create and link to an application.

You can write Blob filters in C or Pascal (or any language that can be called from C). To use your own filters, follow these steps:

1. Decide which filters you need to write.
2. Write the filters in a host language.
3. Build a shared filter library.
4. Make the filter library available.
5. Define the filters to the database.
6. Write an application that requests filtering.

Steps numbered 2, 5, and 6 are described in greater detail in the following ­sections.

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• Declaring an External Blob Filter to the Database