FILTER

A BLOB FILTER is a database object that is a special type of external function, with the sole purpose of taking a BLOB object in one format and converting it to a BLOB object in another format.The formats of the BLOB objects are specified with user-defined BLOB subtypes.

External functions for converting BLOB types are stored in dynamic libraries and loaded when necessary.

For more details on BLOB subtypes, see Binary Data Types.

`DECLARE FILTER`

Declares a BLOB filter in the current database

Available in

DSQL, ESQL

Syntax

DECLARE FILTER filtername
  INPUT_TYPE <sub_type> OUTPUT_TYPE <sub_type>
  ENTRY_POINT 'function_name' MODULE_NAME 'library_name'

<sub_type> ::= number | <mnemonic>

<mnemonic> ::=
    BINARY | TEXT | BLR | ACL | RANGES
  | SUMMARY | FORMAT | TRANSACTION_DESCRIPTION
  | EXTERNAL_FILE_DESCRIPTION | user_defined

Table 1. `DECLARE FILTER` Statement Parameters
Parameter	Description
filtername	Filter name in the database.The maximum length is 63 characters.It need not be the same name as the name exported from the filter library via `ENTRY_POINT`.
sub_type	`BLOB` subtype
number	`BLOB` subtype number (must be negative)
mnemonic	`BLOB` subtype mnemonic name
function_name	The exported name (entry point) of the function
library_name	The name of the module where the filter is located
user_defined	User-defined `BLOB` subtype mnemonic name

The DECLARE FILTER statement makes a BLOB filter available to the database.The name of the BLOB filter must be unique among the names of BLOB filters.