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 Window (Analytical) FunctionsContext Variables 

Function READ_DATA

RDB$BLOB_UTIL.READ_DATA reads chunks of data of a BLOB handle opened with RDB$BLOB_UTIL.OPEN_BLOB.When the BLOB is fully read and there is no more data, it returns NULL.

If LENGTH is passed with a positive number, it returns a VARBINARY with its maximum length.

If LENGTH is NULL it returns a segment of the BLOB with a maximum length of 32765.

Input parameters

  • HANDLE type INTEGER NOT NULL

  • LENGTH type INTEGER

Return type: VARBINARY(32765).

Function SEEK

RDB$BLOB_UTIL.SEEK sets the position for the next READ_DATA, it returns the new position.

MODE may be:

0

from the start
1

from current position
2

from end.

When MODE is 2, OFFSET should be zero or negative.

Input parameters

  • HANDLE type INTEGER NOT NULL

  • MODE type INTEGER NOT NULL

  • OFFSET type INTEGER NOT NULL

Return type: INTEGER NOT NULL.

Note

SEEK only works on stream blobs.Attempting to seek on a segmented blob results in error “invalid BLOB type for operation”.