Re: Proposal: Progressive explain - Mailing list pgsql-hackers

On Fri, Mar 7, 2025 at 6:43 AM Rafael Thofehrn Castro 
<rafaelthca@gmail.com> wrote:
> The wrapper code was implemented by torikoshia 
> (torikoshia(at)oss(dot)nttdata(dot)com),
> so adding the credits here.

On Thu, Mar 20, 2025 at 5:35 AM Robert Haas <robertmhaas@gmail.com> 
wrote:
> Without having the prior discussion near to hand, I *think* that the
> reason we wanted to do this wrap/unwrap stuff is to make it so that
> the progressive EXPLAIN code could only execute when entering a new
> plan node rather than at any random point inside of that plan node,
> and that does seem a lot safer than the alternative.

Your assumption is correct. Various approaches were suggested, such as 
picking a small number of safe and sufficient places for this feature or 
classifying CFI() calls into safe and unsafe ones. However, in the end, 
the wrapping approach [1] was the only one that remained


On 2025-03-30 02:51, Rafael Thofehrn Castro wrote:

> Implemented this version. New patch has the following characteristics:


I haven't looked into the code yet, but when I ran below commands during 
make installcheck, there was an error and an assertion failure

   =# select * from pg_stat_progress_explain;
   =# \watch 0.1

ERROR:  could not attach to dynamic shared area

   WARNING:  terminating connection because of crash of another server 
process
   DETAIL:  The postmaster has commanded this server process to roll back 
the current transaction and exit, because another server process exited 
abnormally and possibly corrupted shared memory.
   HINT:  In a moment you should be able to reconnect to the database and 
repeat your command.
   server closed the connection unexpectedly
           This probably means the server terminated abnormally
           before or while processing the request.
   The connection to the server was lost. Attempting reset: Failed.
   The connection to the server was lost. Attempting reset: Failed.

   TRAP: failed Assert("param->paramkind == PARAM_EXTERN"), File: 
"ruleutils.c", Line: 8802, PID: 73180
   TRAP: failed Assert("param->paramkind == PARAM_EXTERN"), File: 
"ruleutils.c", Line: 8802, PID: 73181
   0   postgres                            0x000000010365f5c4 
ExceptionalCondition + 236
   1   postgres                            0x00000001035a7830 
get_parameter + 1076
   0   postgres                            0x000000010365f5c4 
ExceptionalCondition + 236
   2   postgres                            0x000000010359ff2c 
get_rule_expr + 276
   1   postgres                            0x00000001035a7830 
get_parameter + 1076
   3   postgres                            0x00000001035a841c 
get_rule_expr_paren + 168
   2   postgres                            0x000000010359ff2c 
get_rule_expr + 276
   4   postgres                            0x00000001035a82c4 
get_oper_expr + 292
   3   postgres                            0x00000001035a841c 
get_rule_expr_paren + 168
   5   postgres                            0x00000001035a01f8 
get_rule_expr + 992
   4   postgres                            0x00000001035a82c4 
get_oper_expr + 292
   6   postgres                            0x0000000103598520 
deparse_expression_pretty + 176
   5   postgres                            0x00000001035a01f8 
get_rule_expr + 992
   7   postgres                            0x0000000103598e78 
deparse_expression + 76
   6   postgres                            0x0000000103598520 
deparse_expression_pretty + 176
   8   postgres                            0x0000000102f94198 
show_expression + 100
   7   postgres                            0x0000000103598e78 
deparse_expression + 76
   9   postgres                            0x0000000102f97690 show_qual + 
112
   8   postgres                            0x0000000102f94198 
show_expression + 100
   10  postgres                            0x0000000102f93734 
show_scan_qual + 132
   9   postgres                            0x0000000102f97690 show_qual + 
112
   TRAP: failed Assert("param->paramkind == PARAM_EXTERN"), File: 
"ruleutils.c", Line: 8802, PID: 73183
   11  postgres                            0x0000000102f90680 ExplainNode 
+ 6828
   10  postgres                            0x0000000102f93734 
show_scan_qual + 132
   12  postgres                            0x0000000102f8d398 
ExplainPrintPlan + 540
   0   postgres                            0x000000010365f5c4 
ExceptionalCondition + 236
   11  postgres                            0x0000000102f90680 ExplainNode 
+ 6828
   13  postgres                            0x0000000102f9b974 
ProgressiveExplainPrint + 72
   12  postgres                            0x0000000102f8d398 
ExplainPrintPlan + 540
   1   postgres                            0x00000001035a7830 
get_parameter + 1076
   14  postgres                            0x0000000102f9b920 
ProgressiveExplainStart + 660
   13  postgres                            0x0000000102f9b974 
ProgressiveExplainPrint + 72
   2   postgres                            0x000000010359ff2c 
get_rule_expr + 276
   15  postgres                            0x00000001030771e0 
standard_ExecutorStart + 984
   14  postgres                            0x0000000102f9b920 
ProgressiveExplainStart + 660
   3   postgres                            0x00000001035a841c 
get_rule_expr_paren + 168
   16  postgres                            0x0000000103076de8 
ExecutorStart + 112
   15  postgres                            0x00000001030771e0 
standard_ExecutorStart + 984
   4   postgres                            0x00000001035a82c4 
get_oper_expr + 292
   17  postgres                            0x0000000103080d90 
ParallelQueryMain + 292
   16  postgres                            0x0000000103076de8 
ExecutorStart + 112
   5   postgres                            0x00000001035a01f8 
get_rule_expr + 992
   18  postgres                            0x0000000102df7ef8 
ParallelWorkerMain + 1712
   17  postgres                            0x0000000103080d90 
ParallelQueryMain + 292
   6   postgres                            0x0000000103598520 
deparse_expression_pretty + 176
   19  postgres                            0x00000001032a5d60 
BackgroundWorkerMain + 824
   18  postgres                            0x0000000102df7ef8 
ParallelWorkerMain + 1712
   7   postgres                            0x0000000103598e78 
deparse_expression + 76
   20  postgres                            0x00000001032a9ee8 
postmaster_child_launch + 492
   19  postgres                            0x00000001032a5d60 
BackgroundWorkerMain + 824
   8   postgres                            0x0000000102f94198 
show_expression + 100
   21  postgres                            0x00000001032b4c10 
StartBackgroundWorker + 416
   20  postgres                            0x00000001032a9ee8 
postmaster_child_launch + 492
   9   postgres                            0x0000000102f97690 show_qual + 
112
   22  postgres                            0x00000001032af9d8 
maybe_start_bgworkers + 552
   21  postgres                            0x00000001032b4c10 
StartBackgroundWorker + 416
   10  postgres                            0x0000000102f93734 
show_scan_qual + 132
   23  postgres                            0x00000001032b26cc 
LaunchMissingBackgroundProcesses + 1316
   22  postgres                            0x00000001032af9d8 
maybe_start_bgworkers + 552
   11  postgres                            0x0000000102f90680 ExplainNode 
+ 6828
   24  postgres                            0x00000001032afcb0 ServerLoop 
+ 616
   23  postgres                            0x00000001032b26cc 
LaunchMissingBackgroundProcesses + 1316
   12  postgres                            0x0000000102f8d398 
ExplainPrintPlan + 540
   25  postgres                            0x00000001032ae55c 
PostmasterMain + 6632
   13  postgres                            0x0000000102f9b974 
ProgressiveExplainPrint + 72
   24  postgres                            0x00000001032afcb0 ServerLoop 
+ 616
   25  postgres                            0x00000001032ae55c 
PostmasterMain + 6632
   26  postgres                            0x0000000103121160 main + 952
   27  dyld                                0x000000019cdc0274 start + 
2840
   26  postgres                            0x0000000103121160 main + 952
   27  dyld                                0x000000019cdc0274 start + 
2840
   TRAP: failed Assert("param->paramkind == PARAM_EXTERN"), File: 
"ruleutils.c", Line: 8802, PID: 73182


[1] 
https://www.postgresql.org/message-id/ac6c51071316279bf903078cf264c37a%40oss.nttdata.com

--
Atsushi Torikoshi
Seconded from NTT DATA GROUP CORPORATION to SRA OSS K.K.