On 11/29/2004 10:43 PM, Tom Lane wrote:
Jan Wieck <[EMAIL PROTECTED]> writes:I don't agree that the right cure is to execute each and every statement itself as a subtransaction. What we ought to do is to define a wrapper for the catch Tcl command, that creates a subtransaction and executes the code within during that.
What I would like to do is provide a catch-like Tcl command that defines a subtransaction, and then optimize the SPI commands so that they don't create their own sub-subtransaction if they can see they are directly within the subtransaction command. But when they aren't, they need to define their own subtransactions so that the error semantics are reasonable. I think what you're saying is that a catch command should be exactly equivalent to a subtransaction, but I'm unconvinced --- a catch might be used around some Tcl operations that don't touch the database, in which case the subtransaction overhead would be a serious waste.
That is right. What the catch replacement command should do is to establish some sort of "catch-level", run the script inside the catch block. The first spi operation inside of that block causes a subtransaction to be created and remembered in that catch-level. At the end - i.e. when that block of commands finishes, the subtransaction is committed or rolled back and nothing done if the command block didn't hit any spi statement.
The real point here is that omitting the per-command subtransaction ought to be a hidden optimization, not something that intrudes to the point of having unclean semantics when we can't do it.
We could treat the entire function call as one subtransaction in the first place. Then create more sub-subtransactions as catch blocks appear.
Jan
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