isc_blob_default_desc2()
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Loads a data structure with default information about a Blob, including its subtype, character set, and segment size. For more information about Blob descriptors, see Working with Blob Data.
Syntax
void isc_blob_default_desc2(
ISC_BLOB_DESC_V2 *desc,
unsigned char *table_name,
unsigned char *column_name);
Parameter | Type | Description |
---|---|---|
|
|
Pointer to a Blob descriptor |
|
|
Table name |
|
|
Blob column name |
Description
isc_blob_default_desc2()
loads a Blob descriptor, desc
, with the specified table_name
and column_name
, and the following default values prior to calling isc_blob_gen_bpb2()
to generate a Blob parameter buffer (BPB) for the Blob column being accessed:
- Subtype is set to
TEXT
. - Character set is set to the default character set for the process or database.
- Segment size is set to 80 bytes.
ISC_BLOB_DESC_V2
supports long metadata names of lengthMETADATALENGTH
. The olderISC_BLOB_DESC
structure supports only metadata names of 32 bytes or less.
isc_blob_default_desc2()
and three related functions, isc_blob_gen_bpb2()
, isc_blob_lookup_desc2()
, and isc_blob_set_desc2()
, provide dynamic access to Blob information. In particular, these functions can define and access information about a Blob for filtering purposes, such as character set information for text Blob data, and subtype information for text and non-text Blob data.
The following table lists the fields in the desc
structure:
Parameter | Type | Description |
---|---|---|
blob_desc_version |
short |
Set to |
|
|
Subtype of the Blob filter |
|
|
Character set being used |
|
|
Blob segment size |
|
|
Array containing the name of the Blob column |
|
|
Array containing the name of the table in which the Blob is stored |
Example
The following fragment loads the Blob descriptor with default information:
typedef struct { short blob_desc_version short blob_desc_subtype; short blob_desc_charset; short blob_desc_segment_size; unsigned char blob_desc_field_name[METADATALENGTH]; unsigned char blob_desc_relation_name[METADATALENGTH]; } ISC_BLOB_DESC2; isc_blob_default_desc2(&desc, &relation, &field);
Return value
None.