Re: [HACKERS] This script will crash the connection
Jan Wieck [EMAIL PROTECTED] writes: Tom Lane wrote: The problem here is that the query rewriter tries to hang the query's qualification (WHERE clause) onto the rule's action query, so that the action query won't be done unless the query finds at least one row to update. NOTIFY commands, being utility statements, don't have qualifications. In 7.0 and before, the qual clause just vanished into the ether, and so in this example the NOTIFY would execute whether the UPDATE updated any rows or not. In 7.1 there is physically noplace to hang the qual (no jointree) and thus a crash. Would be something for a STATEMENT trigger. We don't have 'em yet and I'm not sure what kind of information they will receive if we finally implement them. But the number of rows affected by the statement is a good candidate. That's no help for a 7.1 solution however. We can't start inventing a new feature at this stage. What I am inclined to do is have the rewriter reject conditional rules that contain NOTIFY. That seems like the minimal restriction that will prevent a crash or incorrect behavior. Comments? regards, tom lane
Re: [HACKERS] This script will crash the connection
Would be something for a STATEMENT trigger. We don't have 'em yet and I'm not sure what kind of information they will receive if we finally implement them. But the number of rows affected by the statement is a good candidate. That's no help for a 7.1 solution however. We can't start inventing a new feature at this stage. What I am inclined to do is have the rewriter reject conditional rules that contain NOTIFY. That seems like the minimal restriction that will prevent a crash or incorrect behavior. Comments? OK, added to TODO: * Allow NOTIFY in rules and removed from open items list. -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup.| Drexel Hill, Pennsylvania 19026
Re: [HACKERS] This script will crash the connection
Bruce Momjian [EMAIL PROTECTED] writes: OK, added to TODO: * Allow NOTIFY in rules Uh, what does that have to do with the problem? It's certainly not an accurate rendering of either the current or proposed status ... regards, tom lane
Re: [HACKERS] This script will crash the connection
Bruce Momjian [EMAIL PROTECTED] writes: OK, added to TODO: * Allow NOTIFY in rules Uh, what does that have to do with the problem? It's certainly not an accurate rendering of either the current or proposed status ... Oops, can you give me a line. What was the issue? -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup.| Drexel Hill, Pennsylvania 19026
Re: [HACKERS] This script will crash the connection
Bruce Momjian [EMAIL PROTECTED] writes: OK, added to TODO: * Allow NOTIFY in rules Uh, what does that have to do with the problem? It's certainly not an accurate rendering of either the current or proposed status ... Oops, can you give me a line. What was the issue? "Allow NOTIFY in conditional rules" would be an approximation. It's not the whole story though, because presently we also have to fail if the rule is applied to a query with conditions, even if the rule itself is unconditional. As of my last commit: regression=# create rule r1 as on update to int4_tbl do notify foo; CREATE regression=# update int4_tbl set f1 = f1; UPDATE 5 regression=# update int4_tbl set f1 = f1 where f1 0; ERROR: Conditional NOTIFY is not implemented which is pretty ugly but at least it doesn't pretend to do something it can't, which was the 7.0 behavior. (In 7.0 you'd have gotten a NOTIFY whether the update updated any rows or not.) regards, tom lane
Re: [HACKERS] This script will crash the connection
Bruce Momjian [EMAIL PROTECTED] writes: OK, added to TODO: * Allow NOTIFY in rules Uh, what does that have to do with the problem? It's certainly not an accurate rendering of either the current or proposed status ... Oops, can you give me a line. What was the issue? "Allow NOTIFY in conditional rules" would be an approximation. It's not the whole story though, because presently we also have to fail if the rule is applied to a query with conditions, even if the rule itself is unconditional. As of my last commit: regression=# create rule r1 as on update to int4_tbl do notify foo; CREATE regression=# update int4_tbl set f1 = f1; UPDATE 5 regression=# update int4_tbl set f1 = f1 where f1 0; ERROR: Conditional NOTIFY is not implemented which is pretty ugly but at least it doesn't pretend to do something it can't, which was the 7.0 behavior. (In 7.0 you'd have gotten a NOTIFY whether the update updated any rows or not.) Added to TODO: * Allow NOTIFY in rules involving conditionals This covers both cases of conditionals in the rule or the query. -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup.| Drexel Hill, Pennsylvania 19026
Re: [HACKERS] This script will crash the connection
Is there a TODO item here, Tom? "Steve Howe" [EMAIL PROTECTED] writes: create rule blah_update as on update to blah do notify TestEvent; UPDATE blah SET n1=n1+1; -- Won't crash the connection UPDATE blah SET n1=2 WHERE var_field='aaa' AND n1=1 AND n2=2 AND arr_str IS NULL AND m IS NULL; -- Will crash the connection The problem here is that the query rewriter tries to hang the query's qualification (WHERE clause) onto the rule's action query, so that the action query won't be done unless the query finds at least one row to update. NOTIFY commands, being utility statements, don't have qualifications. In 7.0 and before, the qual clause just vanished into the ether, and so in this example the NOTIFY would execute whether the UPDATE updated any rows or not. In 7.1 there is physically noplace to hang the qual (no jointree) and thus a crash. Not sure what to do here. Adding quals to utility statements is right out, however --- even if we weren't late in beta, the concept doesn't make any sense to me. For one reason, utility statements don't have FROM clauses against which to evaluate the quals. I am leaning to the idea that we should forbid NOTIFY in rules altogether. Jan, what's your thought? Steve, your immediate move is to use a trigger rather than a rule to execute the NOTIFY. Meanwhile, we have to think about what to do... regards, tom lane -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup.| Drexel Hill, Pennsylvania 19026
Re: [HACKERS] This script will crash the connection
Bruce Momjian [EMAIL PROTECTED] writes: Is there a TODO item here, Tom? Hopefully we can just decide what to do and do it. I'm waiting to hear Jan's opinion ... regards, tom lane
Re: [HACKERS] This script will crash the connection
Tom Lane wrote: "Steve Howe" [EMAIL PROTECTED] writes: create rule blah_update as on update to blah do notify TestEvent; UPDATE blah SET n1=n1+1; -- Won't crash the connection UPDATE blah SET n1=2 WHERE var_field='aaa' AND n1=1 AND n2=2 AND arr_str IS NULL AND m IS NULL; -- Will crash the connection The problem here is that the query rewriter tries to hang the query's qualification (WHERE clause) onto the rule's action query, so that the action query won't be done unless the query finds at least one row to update. NOTIFY commands, being utility statements, don't have qualifications. In 7.0 and before, the qual clause just vanished into the ether, and so in this example the NOTIFY would execute whether the UPDATE updated any rows or not. In 7.1 there is physically noplace to hang the qual (no jointree) and thus a crash. Not sure what to do here. Adding quals to utility statements is right out, however --- even if we weren't late in beta, the concept doesn't make any sense to me. For one reason, utility statements don't have FROM clauses against which to evaluate the quals. I am leaning to the idea that we should forbid NOTIFY in rules altogether. Jan, what's your thought? Steve, your immediate move is to use a trigger rather than a rule to execute the NOTIFY. Meanwhile, we have to think about what to do... Would be something for a STATEMENT trigger. We don't have 'em yet and I'm not sure what kind of information they will receive if we finally implement them. But the number of rows affected by the statement is a good candidate. Jan -- #==# # It's easier to get forgiveness for being wrong than for being right. # # Let's break this rule - forgive me. # #== [EMAIL PROTECTED] # _ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com
Re: [HACKERS] This script will crash the connection
"Steve Howe" [EMAIL PROTECTED] writes: Please try this script, it will crash the current connection. Crash confirmed. Thanks for the report --- I'm on it... regards, tom lane
Re: [HACKERS] This script will crash the connection
"Steve Howe" [EMAIL PROTECTED] writes: create rule blah_update as on update to blah do notify TestEvent; UPDATE blah SET n1=n1+1; -- Won't crash the connection UPDATE blah SET n1=2 WHERE var_field='aaa' AND n1=1 AND n2=2 AND arr_str IS NULL AND m IS NULL; -- Will crash the connection The problem here is that the query rewriter tries to hang the query's qualification (WHERE clause) onto the rule's action query, so that the action query won't be done unless the query finds at least one row to update. NOTIFY commands, being utility statements, don't have qualifications. In 7.0 and before, the qual clause just vanished into the ether, and so in this example the NOTIFY would execute whether the UPDATE updated any rows or not. In 7.1 there is physically noplace to hang the qual (no jointree) and thus a crash. Not sure what to do here. Adding quals to utility statements is right out, however --- even if we weren't late in beta, the concept doesn't make any sense to me. For one reason, utility statements don't have FROM clauses against which to evaluate the quals. I am leaning to the idea that we should forbid NOTIFY in rules altogether. Jan, what's your thought? Steve, your immediate move is to use a trigger rather than a rule to execute the NOTIFY. Meanwhile, we have to think about what to do... regards, tom lane
