I have noticed HXTT is permanently deleting the records in FoxPro. Is there an option/flag to mark it for deletion?
Within FoxPro deletion is a two-step process. First the record is marked for deletion then you issue a PACK command to permanently remove the record. See image below showing records marked for deletion when browsed in FoxPro
The PACK command requires exclusive access to the table. I am curious as to how this is being done in HXTT when the table is in shared use.
We have been using HXTT for a few years, and never realized that deletion in Foxpro is a two-step process, and I was wondering if the way that HXTT does deletions causes performance issues while doing deletes.
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You can use deletesAreVisible=true connection property to see the deleted rows.
deletesAreVisible: Indicates whether DBF's resultSet includes deleted records. false
DELETED([cTableAlias | nWorkArea]): returns a logical value that indicates whether the current record is marked for deletion.
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I'm aware of the deletesAreVisible flag, my question, more precisely, is what does HXTT do when it receives an SQL statement that calls delete for a number of records. Are those records simply marked for deletion, or does HXTT do a mark for delete followed by a pack to actually delete the records from the table. I think it is doing the latter, because the records I'm deleting are in fact removed from the table. I'm asking because I'm trying to isolate a performance issue, and I'm trying to rule out a speed degradation due to the need for an exclusive lock to do the pack operation after a mark for delete.
Thanks!
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> Are those records simply marked for deletion,
Yeah. If deletesAreBlank=false(default connection property), you can undelete it. If deletesAreBlank=true, it becomes a blank data row.
deletesAreBlank Indicates whether one destination data record will become one deleted blank record when delete it. false
>does HXTT do a mark for delete followed by a pack to
>actually delete the records from the table.
Pack Table sql can do it, but HXTT DBF markes a deleted flag.
>because the records I'm deleting are in fact removed from the table.
You can see those deleted rows if you use deletesAreVisible=true connetion property in that(or latter) connection.
>the need for an exclusive lock to do the pack operation after a mark for delete.
Yeah. Pack table sql need an exclusive lock.
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