首先,我将图像的BLOB转换为CLOB,然后将该CLOB转换回BLOB。我看不到重新转换的图像。我该如何解决这个问题?
blob_to_clob函数:
CREATE OR REPLACE FUNCTION blob_to_clob (blob_in IN BLOB) RETURN CLOB AS
v_clob CLOB;
v_varchar VARCHAR2(32767);
v_start PLS_INTEGER := 1;
v_buffer PLS_INTEGER := 32767;
BEGIN
DBMS_LOB.CREATETEMPORARY(v_clob, TRUE);
FOR i IN 1..CEIL(DBMS_LOB.GETLENGTH(blob_in) / v_buffer)
LOOP
v_varchar := UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(blob_in, v_buffer, v_start));
DBMS_LOB.WRITEAPPEND(v_clob, LENGTH(v_varchar), v_varchar);
v_start := v_start + v_buffer;
END LOOP;
RETURN v_clob;
END blob_to_clob;
clob_to_blob功能:
CREATE OR REPLACE FUNCTION clob_to_blob2(p_clob IN CLOB) RETURN BLOB IS
v_blob BLOB;
v_offset NUMBER DEFAULT 1;
v_amount NUMBER DEFAULT 4096;
v_offsetwrite NUMBER DEFAULT 1;
v_amountwrite NUMBER;
v_buffer VARCHAR2(4096 CHAR);
BEGIN dbms_lob.createtemporary(v_blob, TRUE);
Begin
LOOP
dbms_lob.READ (lob_loc => p_clob,
amount => v_amount,
offset => v_offset,
buffer => v_buffer);
v_amountwrite := utl_raw.length (r => utl_raw.cast_to_raw(c => v_buffer));
dbms_lob.WRITE (lob_loc => v_blob,
amount => v_amountwrite,
offset => v_offsetwrite,
buffer => utl_raw.cast_to_raw(v_buffer));
v_offsetwrite := v_offsetwrite + v_amountwrite;
v_offset := v_offset + v_amount;
v_amount := 4096;
END LOOP;
EXCEPTION
WHEN no_data_found THEN
NULL;
End;
RETURN v_blob;
END clob_to_blob2;
答案 0 :(得分:3)
这样的代码将执行最少的重新编码:
create or replace function clob2blob(AClob CLOB) return BLOB is
Result BLOB;
o1 integer;
o2 integer;
c integer;
w integer;
begin
o1 := 1;
o2 := 1;
c := 0;
w := 0;
DBMS_LOB.CreateTemporary(Result, true);
DBMS_LOB.ConvertToBlob(Result, AClob, length(AClob), o1, o2, 0, c, w);
return(Result);
end clob2blob;
/
但是CLOB无法正确包含所有图像数据而没有像Base64这样的编码
答案 1 :(得分:0)
您可以使用:
CREATE FUNCTION clob_to_blob(
value IN CLOB,
charset_id IN INTEGER DEFAULT DBMS_LOB.DEFAULT_CSID,
error_on_warning IN NUMBER DEFAULT 0
) RETURN BLOB
IS
result BLOB;
dest_offset INTEGER := 1;
src_offset INTEGER := 1;
lang_context INTEGER := DBMS_LOB.DEFAULT_LANG_CTX;
warning INTEGER;
warning_msg VARCHAR2(50);
BEGIN
DBMS_LOB.CreateTemporary(
lob_loc => result,
cache => TRUE
);
DBMS_LOB.CONVERTTOBLOB(
dest_lob => result,
src_clob => value,
amount => LENGTH( value ),
dest_offset => dest_offset,
src_offset => src_offset,
blob_csid => charset_id,
lang_context => lang_context,
warning => warning
);
IF warning != DBMS_LOB.NO_WARNING THEN
IF warning = DBMS_LOB.WARN_INCONVERTIBLE_CHAR THEN
warning_msg := 'Warning: Inconvertible character.';
ELSE
warning_msg := 'Warning: (' || warning || ') during CLOB conversion.';
END IF;
IF error_on_warning = 0 THEN
DBMS_OUTPUT.PUT_LINE( warning_msg );
ELSE
RAISE_APPLICATION_ERROR(
-20567, -- random value between -20000 and -20999
warning_msg
);
END IF;
END IF;
RETURN result;
END clob_to_blob;
/