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+ Patch from Bram Kuijvenhoven: optimised storage of zero-length BLOBS

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git-svn-id: trunk@3469 -
This commit is contained in:
michael 2006-05-10 09:05:15 +00:00
parent 516e94be11
commit 32e0de3ba7
1 changed files with 16 additions and 11 deletions
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27
fcl/db/sqldb/odbc/odbcconn.pas
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@ -102,8 +102,8 @@ type
public
property Environment:TODBCEnvironment read FEnvironment;
published
property Driver:string read FDriver write FDriver; // will be passed as DRIVER connection parameter
property FileDSN:string read FFileDSN write FFileDSN; // will be passed as FILEDSN parameter
property Driver:string read FDriver write FDriver; // will be passed as DRIVER connection parameter
property FileDSN:string read FFileDSN write FFileDSN; // will be passed as FILEDSN parameter
// Redeclare properties from TSQLConnection
property Password; // will be passed as PWD connection parameter
property Transaction;
@ -599,11 +599,14 @@ begin
else
BlobBufferSize:=DEFAULT_BLOB_BUFFER_SIZE;
try
// Allocate the buffer and memorystream
BlobBuffer:=GetMem(BlobBufferSize);
BlobMemoryStream:=TMemoryStream.Create;
if BlobBufferSize>0 then
// init BlobBuffer and BlobMemoryStream to nil pointers
BlobBuffer:=nil;
BlobMemoryStream:=nil;
if BlobBufferSize>0 then // Note: zero-length BLOB is represented as nil pointer in the field buffer to save memory usage
begin
// Allocate the buffer and memorystream
BlobBuffer:=GetMem(BlobBufferSize);
BlobMemoryStream:=TMemoryStream.Create;
// Retrieve data in parts (or effectively in one part if StrLenOrInd<>SQL_NO_TOTAL above)
repeat
Res:=SQLGetData(ODBCCursor.FSTMTHandle, FieldDef.Index+1, SQL_C_BINARY, BlobBuffer, BlobBufferSize, @StrLenOrInd);
@ -618,12 +621,14 @@ begin
end;
// Store memorystream pointer in Field buffer and in the cursor's FBlobStreams list
TObject(buffer^):=BlobMemoryStream;
ODBCCursor.FBlobStreams.Add(BlobMemoryStream);
if BlobMemoryStream<>nil then
ODBCCursor.FBlobStreams.Add(BlobMemoryStream);
// Set BlobMemoryStream to nil, so it won't get freed in the finally block below
BlobMemoryStream:=nil;
finally
BlobMemoryStream.Free;
Freemem(BlobBuffer,BlobBufferSize);
if BlobBuffer<>nil then
Freemem(BlobBuffer,BlobBufferSize);
end;
end;
end;
@ -642,12 +647,12 @@ var
ODBCCursor: TODBCCursor;
BlobMemoryStream, BlobMemoryStreamCopy: TMemoryStream;
begin
// TODO: implement TODBCConnection.CreateBlobStream
if Mode=bmRead then
if (Mode=bmRead) and not Field.IsNull then
begin
Field.GetData(@BlobMemoryStream);
BlobMemoryStreamCopy:=TMemoryStream.Create;
BlobMemoryStreamCopy.LoadFromStream(BlobMemoryStream);
if BlobMemoryStream<>nil then
BlobMemoryStreamCopy.LoadFromStream(BlobMemoryStream);
Result:=BlobMemoryStreamCopy;
end
else