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What is the best practice for using MySqlDataReader for multiple query's ?

I have a procedure that does something like below. The problem is that the MySqlDataReader gets corrupted after 5-6 iterations.

I noticed that if I do a closeConnection then openConnection, I do not get any corruption in the MySqlDataReader.

MySqlDataReader mr;

for many transaction types:
OpenDataSet(sqlStmt)

procedure OpenDataSet(string sqlStmt)
if ( mr != null && !mr.IsClosed ) mr.Close()
// if closeConnection here then all is fine.
if ( connection not open) openConnection()
mr = ExecuteReader()
case transactionType
do your thing
mr.Close()

MyDAC v 5.55.0.39 for Delphi-6

MyQuery.Params.ParamByName(fnBlob).SetBlobData(BlobData,Bytes - BytesWritten)

does not work when the data has \0 values.

How can I accomplish this ? i.e. how to escape the binary data?

I currently have to do the following:

ms := TMemoryStream.Create;
ms.WriteBuffer(BlobData^, Bytes - BytesWritten);
ms.Position := 0;
MyQuery.Params.ParamByName(fnBlob).LoadFromStream(ms,ftBlob);
ms.Free;

thx

hello,

more info.

same code/config under MySql 5.0.20a-nt-log results:

select
replace(r.proc_path
,"Reports.exe" # 11 chars
,"Reports2.exe" # 12 chars
) proc_path2
,r.proc_path
from proc_run r

fieldByName('proc_path2').Size: 109
fieldByName('proc_path').Size: 100

If I replace valueA with valueB where valueB is larger in size, I get truncated data. if valueB is smaller or of equal size then truncation does NOT occur.

forgot config.

Delphi 6 sp2
MySql 3.23.58
MyDAC 5.55.0.39

hello,

Delphi 6 sp2
MySql 3.23.58
MyDAC 5.55.0.39

I'm having trouble with a Field.Size for sql stmt below.
I cannot figure out why data is being truncated at field level
where the mysql client program handles it just fine.

mysql> desc proc_run;
+------------+-----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-----------+------+-----+---------+-------+
| proc_key | char(5) | | PRI | | |
| proc_name | char(40) | | PRI | | |
| proc_host | char(25) | | | | |
| proc_path | char(100) | | | | |
| proc_parms | char(100) | | | | |
+------------+-----------+------+-----+---------+-------+
5 rows in set (0.00 sec)

-- Data truncated here
select
replace(r.proc_path
,"Reports.exe" # 11 chars
,"Reports2.exe" # 12 chars
) proc_path2
,r.proc_path
from proc_run r

fieldByName('proc_path2').Size: 10
fieldByName('proc_path').Size: 100

-- Data NOT truncated here

select
replace(r.proc_path
,"Reports.exe" # 11 chars
,"Reports2.xe" # 11 chars
) proc_path2
,r.proc_path
from proc_run r

fieldByName('proc_path2').Size: 100
fieldByName('proc_path').Size: 100

Hello,

I had a MySql concat function truncating at 8192 chars. I set Options.LongString=False and was able to avoid string truncation.

Ae their any consequences to leaving LongString=False at all times?
e.g. performance,

I used this particualr query to retrieve single fields, one row (i.e. As a function).

JohnC

Sorry, but I should have given more details.

I understand I can handle this programmatically .AsString but my problem is that when using 3rd party components (like RaveReports), it directly reads the Table and Field as TString under Zeos and TDateTime under MyDAC.

Can this only be addressed by acquiring the source code and making modifications?

Hello,

I'm swapping out data access components from Zeos to MyDAC. The MySql column type TimeStamp(14) is returned as follows:

Zeos : TStringField
MyDac: TDateTime

How can I get the MyDAC components to treat the MySql TimeStamp column to be returned as a TStringField ?

Cannot tell what the 5th replace statment is (\r)?

Serious wrote:We do not provide public method for string escaping.
Here is the simplest example of the string escaping in MySQL way.

Code: Select all

string EscapeString(string s)
{
	s = s.Replace("\", "\");
	s = s.Replace("\", "\");
	s = s.Replace(""", "\"");
	s = s.Replace("`", "\`");
	s = s.Replace("ґ", "\ґ");
	s = s.Replace("’", "\’");
	s = s.Replace("‘", "\‘");
	return s;
}

If I use Parameters, are the strings escaped?