Trong trường hợp văn bản của bạn được nén bên trong blob bằng thuật toán DEFLATE và nó khá lớn, bạn có thể sử dụng chức năng này để đọc nó
CREATE OR REPLACE PACKAGE read_gzipped_entity_package AS
FUNCTION read_entity(entity_id IN VARCHAR2)
RETURN VARCHAR2;
END read_gzipped_entity_package;
/
CREATE OR REPLACE PACKAGE BODY read_gzipped_entity_package IS
FUNCTION read_entity(entity_id IN VARCHAR2) RETURN VARCHAR2
IS
l_blob BLOB;
l_blob_length NUMBER;
l_amount BINARY_INTEGER := 10000; -- must be <= ~32765.
l_offset INTEGER := 1;
l_buffer RAW(20000);
l_text_buffer VARCHAR2(32767);
BEGIN
-- Get uncompressed BLOB
SELECT UTL_COMPRESS.LZ_UNCOMPRESS(COMPRESSED_BLOB_COLUMN_NAME)
INTO l_blob
FROM TABLE_NAME
WHERE ID = entity_id;
-- Figure out how long the BLOB is.
l_blob_length := DBMS_LOB.GETLENGTH(l_blob);
-- We'll loop through the BLOB as many times as necessary to
-- get all its data.
FOR i IN 1..CEIL(l_blob_length/l_amount) LOOP
-- Read in the given chunk of the BLOB.
DBMS_LOB.READ(l_blob
, l_amount
, l_offset
, l_buffer);
-- The DBMS_LOB.READ procedure dictates that its output be RAW.
-- This next procedure converts that RAW data to character data.
l_text_buffer := UTL_RAW.CAST_TO_VARCHAR2(l_buffer);
-- For the next iteration through the BLOB, bump up your offset
-- location (i.e., where you start reading from).
l_offset := l_offset + l_amount;
END LOOP;
RETURN l_text_buffer;
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE('!ERROR: ' || SUBSTR(SQLERRM,1,247));
END;
END read_gzipped_entity_package;
/
Sau đó chạy chọn để nhận văn bản
SELECT read_gzipped_entity_package.read_entity('entity_id') FROM DUAL;
Hy vọng điều này sẽ giúp một ai đó.
