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BLOB handling for client |
Sun, Oct 29 2006 6:40 PM | Permanent Link |
"Glynn Owen" | I need to have my server send blobs to a client. I would like to do
this so that the client doesn't receive the contents of any blob until those contents are specifically requested. I'm using TDBISAMQuery components for the data transfer. I have a primary table on display with a lot of controls that allow for user-defined queries. I could put the blobs in a separate table linked by a key to the primary table, and then run a separate query on request, but I'm wondering if there might be a better way to do this. Any suggestions would be welcome. TIA, Glynn |
Mon, Oct 30 2006 9:09 AM | Permanent Link |
"David Farrell-Garcia" | Glynn Owen wrote:
> I need to have my server send blobs to a client. I use ClientDataSets with / Dbisam so I normally fetchBlobs only when I request them, but in your case why not just do a separate query to fetch the blob forthe current record when the end-user requests it? -- David Farrell-Garcia Whidbey Island Software, LLC |
Mon, Oct 30 2006 10:03 AM | Permanent Link |
"Glynn Owen" | David Farrell-Garcia wrote:
> Glynn Owen wrote: > > > I need to have my server send blobs to a client. > > I use ClientDataSets with / Dbisam so I normally fetchBlobs only when > I request them, but in your case why not just do a separate query to > fetch the blob forthe current record when the end-user requests it? No compelling reason. It's just that in reading over the documentation, I have the impression that what I'm trying to do may be a feature of DBISAM that I don't yet understand, so I thought I would ask. Otherwise, your suggestion does provide an alternative to my own that has the advantage of not requiring another table. Thanks, Glynn |
Mon, Oct 30 2006 2:49 PM | Permanent Link |
Jason Lee | Data in blobs aren't sent to the client unless there is a data-aware
control (dbgrid, dbmemo control, dbpicture control, etc.) that is expecting them or the blob's field contents are specifically accessed. Glynn Owen wrote: > I need to have my server send blobs to a client. I would like to do > this so that the client doesn't receive the contents of any blob until > those contents are specifically requested. I'm using TDBISAMQuery > components for the data transfer. I have a primary table on display > with a lot of controls that allow for user-defined queries. > > I could put the blobs in a separate table linked by a key to the > primary table, and then run a separate query on request, but I'm > wondering if there might be a better way to do this. Any suggestions > would be welcome. > > TIA, Glynn |
Mon, Oct 30 2006 3:56 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. timyoung@elevatesoft.com | Glynn,
<< I need to have my server send blobs to a client. I would like to do this so that the client doesn't receive the contents of any blob until those contents are specifically requested. I'm using TDBISAMQuery components for the data transfer. I have a primary table on display with a lot of controls that allow for user-defined queries. >> Jason is correct - this is how DBISAM works by default. -- Tim Young Elevate Software www.elevatesoft.com |
Mon, Oct 30 2006 5:29 PM | Permanent Link |
"Glynn Owen" | Jason Lee wrote:
> Data in blobs aren't sent to the client unless there is a data-aware > control (dbgrid, dbmemo control, dbpicture control, etc.) that is > expecting them or the blob's field contents are specifically accessed. > > Glynn Owen wrote: > > I need to have my server send blobs to a client. I would like to do > > this so that the client doesn't receive the contents of any blob > > until those contents are specifically requested. I'm using > > TDBISAMQuery components for the data transfer. I have a primary > > table on display with a lot of controls that allow for user-defined > > queries. > > > > I could put the blobs in a separate table linked by a key to the > > primary table, and then run a separate query on request, but I'm > > wondering if there might be a better way to do this. Any suggestions > > would be welcome. > > > > TIA, Glynn I am using a DBGrid. From what you (and Tim) said, it may be a workable plan to - a) disconnect the query from the datasource of the grid. b) run the query c) locate the blob field and set its visible property to FALSE d) reconnect the query to the datasource Hopefully, this will leave the blob field accessible by code, but not accessed by the grid. Guess I'll give it a whirl and see what happens. Thanks for your help, Glynn |
Mon, Oct 30 2006 7:45 PM | Permanent Link |
Jason Lee | -or-
if it is logistically feasible, do not include the blob field in the set of fields that are displayed in the dbgrid Glynn Owen wrote: > I am using a DBGrid. From what you (and Tim) said, it may be a workable > plan to - > > a) disconnect the query from the datasource of the grid. > b) run the query > c) locate the blob field and set its visible property to FALSE > d) reconnect the query to the datasource > > Hopefully, this will leave the blob field accessible by code, but not > accessed by the grid. > > Guess I'll give it a whirl and see what happens. |
Tue, Oct 31 2006 8:41 AM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. timyoung@elevatesoft.com | Glynn,
<< I am using a DBGrid. From what you (and Tim) said, it may be a workable plan to - >> Actually, Jason is correct again - the easiest method is to simply not include the BLOB field in the list of fields used by the grid control. That will prevent the grid from doing anything with the BLOB field. -- Tim Young Elevate Software www.elevatesoft.com |
Tue, Oct 31 2006 2:59 PM | Permanent Link |
"Glynn Owen" | Tim Young [Elevate Software] wrote:
> Glynn, > > << I am using a DBGrid. From what you (and Tim) said, it may be a > workable plan to - >> > > Actually, Jason is correct again - the easiest method is to simply > not include the BLOB field in the list of fields used by the grid > control. That will prevent the grid from doing anything with the > BLOB field. Yes, but that seems to be throwing out the baby with the bathwater. I'm trying to avoid doing a second query just to fetch the blob field. Thanks for your help, Glynn -- http://realthinclient.com |
Tue, Oct 31 2006 3:30 PM | Permanent Link |
Jason Lee | You can use the same query, just don't display the blob field in your
grid initially....(hint: double-click the dbgrid at design-time to get a field list) Glynn Owen wrote: > Yes, but that seems to be throwing out the baby with the bathwater. I'm > trying to avoid doing a second query just to fetch the blob field. |
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