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To work with Blob data that must be filtered, an API application must set up a Blob parameter buffer (BPB) for each Blob. A BPB is a variable-length byte vector declared in an application to store control information that dictates Blob access. The BPB can contain a number of constants, defined in
ibase.h, that describe the Blob and the Blob subtypes that specify Blob filtering.
Applications that work with Blob data in an international environment must also declare and populate a Blob descriptor that contains character set information for the Blob. The Blob descriptor structure is defined in
ibase.h. To declare a Blob descriptor, an application must provide code like this:
#include <ibase.h> . . . ISC_BLOB_DESC_V2 descriptor_name;
Blob filters enable a Blob to be translated from one format to another, such as from a compressed state to an decompressed state or vice versa. If Blob filters are desired, separate filter functions must be created and defined to the database to ensure their use when Blob data is accessed.
Finally, to access Blob data, applications must make extensive use of API DSQL functions.
For more information about working with Blob data and Blob filters, see Working with Blob Data.
For more information about DSQL, see Working with Dynamic SQL.