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Downside to a duplicate XResultSetClose (Read 903 times)

lksseven Full Member Offline Posts: 416 Location: Southwest Joined: Jan 26^th, 2009	Downside to a duplicate XResultSetClose Apr 20^th, 2012 at 2:53am	Print Post
	I now have personal knowledge of the downside (locked records, irritation) to an @XResultSetSearch statement that is not properly mated with an XResultSetClose statement. But, is there a downside to an inadvertent extra XResultSetClose statement?

	Larry
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Hammer YaBB Administrator Lanticans Offline Fire bad. Tree pretty. Posts: 3436 Location: Ohio Joined: Nov 22^nd, 2002	Re: Downside to a duplicate XResultSetClose Reply #1 - Apr 20^th, 2012 at 1:52pm	Print Post
	lksseven wrote on Apr 20^th, 2012 at 2:53am: But, is there a downside to an inadvertent extra XResultSetClose statement? It can result in you closing an XResultSet you didn't intend to. You want to have exactly as many closes as opens. The structure you want is: vRS = @XResultSetSearch(...) If vRS > -1 { Do stuff ... XResultSetClose(vRS) } If it opened successfully, close it. Once.

	- Hammer The plural of anecdote is not data.
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lksseven Full Member Offline Posts: 416 Location: Southwest Joined: Jan 26^th, 2009	Re: Downside to a duplicate XResultSetClose Reply #2 - Apr 20^th, 2012 at 4:09pm	Print Post
	Erica, I was just thinking in terms of trouble-shooting ... scenario: my recent scenario: an application with involved/complex code is having lockup problems, and a missing XResultSetClose is suspected as the culprit ... I didn't know for sure that a missing XResultSetClose was the problem (it could have been a hardware issue (router, server, client, cabling). It occurred to me (after I found the solution the hard way, of course, and also replaced two network switches and replaced 2 cable runs just for good measure while I went through code with a fine tooth comb) "what if I just went into each event and put an XResultSetClose for each "vRS" as the last thing before the final "}" in that event, then reconciled and tested?" If I had done that and my lockups had gone away, then I would have quickly at least identified that the needle was in the 'programming haystack' instead of maybe being in the 'hardware malfunction haystack', and kick started me in the right direction to find the missing statement (or misplaced statement). I just didn't want to keep that in my back pocket for the future if there was going to be a damaging downside to doing so (database corruption, massive hole created in the ozone, etc).

	Larry
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The Cow YaBB Administrator Offline Posts: 2530 Joined: Nov 22^nd, 2002	Re: Downside to a duplicate XResultSetClose Reply #3 - Apr 20^th, 2012 at 4:30pm	Print Post
	There is no harm so long as you are closing the same result set that you previously opened and closed. But the scenario Erika described does need to be avoided. A result set handle is simply an index into an array of indexes. When you open a result set the actual engine-side index is placed in the client side array. When you close it, that array entry can then be reused. If it has been reused, and you close it again, you are closing the wrong result set. Its not going to harm anything in and of itself. But any decision your code makes about the incorrectly closed secondary (or tertiary) result set, may cause harm.

	Mark Lasersohn&&Programmer&&Lantica Software, LLC
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Bharat_Naik Senior Member Members Offline Ever ready to learn and share Posts: 1202 Location: Chicago, Illinois Joined: Dec 16^th, 2003	Re: Downside to a duplicate XResultSetClose Reply #4 - Apr 20^th, 2012 at 4:52pm	Print Post
	Is it advisable to use different Resultset name instead of using the same one again and again? My tendency is to use name RSHandlle. I can see this could conflict sometimes if you try to open more than two at the same time with the same name and not closing properly before opening up the other one.


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The Cow YaBB Administrator Offline Posts: 2530 Joined: Nov 22^nd, 2002	Re: Downside to a duplicate XResultSetClose Reply #5 - Apr 20^th, 2012 at 6:15pm	Print Post
	Bharat_Naik wrote on Apr 20^th, 2012 at 4:52pm: Is it advisable to use different Resultset name instead of using the same one again and again?� My tendency is to use name RSHandlle. I can see this could conflict sometimes if you try to open more than two at the same time with the same name and not closing properly before opening up the other one. It depends on the scope of the variable. If global, then - yes, always use different names if there is any possibility of multiple open result sets. If the scope is local, its fine to use a generic name, so long as each open result set is addressed in a different event or subroutine. And, try to use local variables where ever possible. Prefer locals over globals, and globals over fields/elements. Using either, be careful for this case: Code var aa as int aa = Open(1) if(aa > -1) { aa = Open(2) if(aa > -1) { close(aa) } close(aa) } In the case above, the result set first opened, is never closed.

	Mark Lasersohn&&Programmer&&Lantica Software, LLC
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lksseven Full Member Offline Posts: 416 Location: Southwest Joined: Jan 26^th, 2009	Re: Downside to a duplicate XResultSetClose Reply #6 - Apr 20^th, 2012 at 11:36pm	Print Post
	Bharat, I always (almost always) use different names for different XResultSetSearches (vRS1,� vRS2,� vRS3, etc)� because - for me - it's the only way to keep them straight without my eyes swimming into one big blur. Just as an aside comment, I also label my beginning and ending "{" brackets to make it easier to 'see the entire playing field in a complex event where I have to scroll several pages down in the programming editor.� �I don't know if it's a dumb idea or not, but it works for me.� As in: If @Mode() = 0 � { // A� begins 'if @Mode() = 0' � �� vRS1 = @XResultSetSearch(....) � �� vRS1Tot = @XResultSetTotal(vRS1) � �� If vRS1Tot = 1 � �� { // B begins 'if vRS1Tot = 1' � �� a bunch of programming lines here � �� } // B ends 'if vRS1Tot = 1' � �� XResultSetClose(vRS1) � �} // A ends 'if @Mode() = 0' Actually, it would be really nice if the program editor was capable of making different font colors�

	Larry
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Carl Underwood Senior Member Members Offline Posts: 1351 Location: New Hampshire Joined: Mar 11^th, 2003	Re: Downside to a duplicate XResultSetClose Reply #7 - Apr 21^st, 2012 at 12:13am	Print Post
	lksseven wrote on Apr 20^th, 2012 at 11:36pm: Actually, it would be really nice if the program editor was capable of making different font colors� Huh That may be nice, but it would certainly cause a problem with the Syntax Highlighting feature. But, what would be GREAT, would be if the curly braces could dynamically change to another color (in pairs) or be highlighted when the cursor was placed next to one of them. Many text editors designed for programming do this. They automatically locate the matching component when you put the cursor immediately before or after the item in question. Maybe this should be a requested feature for version 3?

	Carl Underwood CDU Computer Consulting LLC Epsom, New Hampshire
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