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Re: Segfaults and assertion failures with not too extraordinary views and queries

From: Phil Frost <phil(at)macprofessionals(dot)com>
To: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Segfaults and assertion failures with not too extraordinary views and queries
Date: 2007-02-15 18:25:07
Message-ID: (view raw or flat)
Lists: pgsql-bugs
Yeah, maybe I am the only one doing this to the planner. The  
optimizations which caused this error will be greatly appreciated  
when I stop getting segfaults, however :)

I rebuilt my pg with the attached patch and it did indeed resolve the  
assertion failure the previous test produced. I tinkered some more  
and got this patched build to segfault with a slightly different  
script, below.

Part of the funkiness seems to be in that the view is recursive;  
orderitem_with_prices calls sum_of_subitem_total_taxable_prices,  
which queries orderitem_with_prices. I would not be suprised if no  
one else is doing this, since I think the only way to get it done  
under normal conditions is to create an empty function first (since  
the view doesn't exist), make the view, then replace the function; or  
to set check_function_bodies = false. As weird as it is though, it  
worked in 8.1 and a segfault is bad in any case.


SET check_function_bodies = false;
SET client_min_messages = warning;


CREATE TABLE private.orderitem (
     objectid integer,
     showsubitems boolean,
     longdescription character varying,
     showsubitemprices boolean,
     quantity numeric,
     sortorder real,
     superitem integer,
     notes character varying,
     name character varying,
     "order" integer

CREATE FUNCTION public.i_have_global_priv() RETURNS boolean
     AS $$
     select true

CREATE VIEW public.orderitem AS
     SELECT orderitem.objectid,
     FROM private.orderitem WHERE i_have_global_priv();

CREATE FUNCTION public.sum_of_subitem_total_taxable_prices(integer)  
RETURNS numeric
     AS $_$
     select 1.0 from orderitem_with_prices where superitem = $1  --  
changing this to just "select 1.0" avoids the problem

CREATE TABLE private.orderitemproduct (
     objectid integer

CREATE VIEW public.orderitemproduct AS
     SELECT orderitemproduct.objectid
     FROM private.orderitemproduct WHERE i_have_global_priv();

CREATE VIEW public.orderitem_with_prices AS
     SELECT orderitem.objectid,
     sum_of_subitem_total_taxable_prices(orderitem.objectid) AS  
     FROM (orderitem LEFT JOIN orderitemproduct USING (objectid));

insert into private.orderitem(objectid) select generate_series(1, 6000);
insert into private.orderitem(objectid, superitem) select  
generate_series(6001, 12000), generate_series(1, 6000);

insert into private.orderitemproduct(objectid) select generate_series 
(1, 6000);

ALTER TABLE ONLY private.orderitem
     ADD CONSTRAINT orderitem_pkey PRIMARY KEY (objectid);

ALTER TABLE ONLY private.orderitemproduct
     ADD CONSTRAINT orderitemproduct_pkey PRIMARY KEY (objectid);


To produce the segfault, I do this:

vacuum analyze;
set enable_seqscan = 0;
prepare crash as select * from orderitem_with_prices limit 1;
explain execute crash;
execute crash;

The error seems to depend on the plan chosen; here it won't fail if I  
don't vacuum. The plan generated for me is:

                                                         QUERY PLAN
Limit  (cost=0.01..0.06 rows=1 width=8)
    ->  Result  (cost=0.01..680.51 rows=12000 width=8)
          One-Time Filter: i_have_global_priv()
          ->  Merge Left Join  (cost=0.01..650.51 rows=12000 width=8)
                Merge Cond: (private.orderitem.objectid =  
                ->  Index Scan using orderitem_pkey on orderitem   
(cost=0.00..361.25 rows=12000 width=8)
                ->  Result  (cost=0.00..184.25 rows=6000 width=4)
                      One-Time Filter: i_have_global_priv()
                      ->  Index Scan using orderitemproduct_pkey on  
orderitemproduct  (cost=0.00..184.25 rows=6000 width=4)

I get this backtrace:

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x0000000c
ExecEvalVar (exprstate=0xed0aec, econtext=0xed0b08, isNull=0xbfffc5c8  
"????", isDone=0x0) at execQual.c:496
496                             TupleDesc       slot_tupdesc = slot- 
(gdb) bt
#0  ExecEvalVar (exprstate=0xed0aec, econtext=0xed0b08,  
isNull=0xbfffc5c8 "????", isDone=0x0) at execQual.c:496
#1  0x000e9304 in ExecEvalExprSwitchContext (expression=0xed0aec,  
econtext=0xed0b08, isNull=0xbfffc5c8 "????", isDone=0x0) at  
#2  0x000f5750 in ExecIndexEvalRuntimeKeys (econtext=0xed0b08,  
runtimeKeys=0xed0b08, numRuntimeKeys=1) at nodeIndexscan.c:249
#3  0x000f5810 in ExecIndexReScan (node=0xed0458, exprCtxt=0xed0b08)  
at nodeIndexscan.c:202
#4  0x000e2040 in ExecReScan (node=0xed0458, exprCtxt=0x20692ec) at  
#5  0x000e1ff0 in ExecReScan (node=0x206a5a8, exprCtxt=0x20692ec) at  
#6  0x000f7f88 in ExecNestLoop (node=0x2069260) at nodeNestloop.c:162
#7  0x000e59e0 in ExecProcNode (node=0x2069260) at execProcnode.c:382
#8  0x000f8a5c in ExecResult (node=0x2068cb4) at nodeResult.c:130
#9  0x000e5950 in ExecProcNode (node=0x2068cb4) at execProcnode.c:334
#10 0x000e405c in ExecutorRun (queryDesc=0xeccef4,  
direction=ForwardScanDirection, count=1) at execMain.c:1082
#11 0x000eee44 in postquel_getnext (es=0xece2b8) at functions.c:359
#12 0x000eff98 in fmgr_sql (fcinfo=0xbfffcdf8) at functions.c:460
#13 0x000e8fe8 in ExecMakeFunctionResult (fcache=0x2072794,  
econtext=0x2072664, isNull=0xec4fca "", isDone=0xec5030) at  
#14 0x000e99b0 in ExecProject (projInfo=0x2072bec, isDone=0xbfffd108)  
at execQual.c:4119
#15 0x000f8a90 in ExecResult (node=0x20725d8) at nodeResult.c:157
#16 0x000e5950 in ExecProcNode (node=0x20725d8) at execProcnode.c:334
#17 0x000fa268 in ExecLimit (node=0x20724b4) at nodeLimit.c:84
#18 0x000e5a80 in ExecProcNode (node=0x20724b4) at execProcnode.c:425
#19 0x000e405c in ExecutorRun (queryDesc=0x205f048,  
direction=ForwardScanDirection, count=0) at execMain.c:1082
#20 0x0018567c in PortalRunSelect (portal=0x20466a8, forward=1  
'\001', count=0, dest=0x204603c) at pquery.c:831
#21 0x00186ef8 in PortalRun (portal=0x20466a8, count=2147483647,  
dest=0x204603c, altdest=0x204603c, completionTag=0x0) at pquery.c:656
#22 0x000bc7b4 in ExecuteQuery (stmt=0x2031cf0, params=0x0,  
dest=0x204603c, completionTag=0x0) at prepare.c:216
#23 0x00185d60 in PortalRunUtility (portal=0x204661c,  
query=0x2031d98, dest=0x204603c, completionTag=0x0) at pquery.c:1063
#24 0x00186900 in FillPortalStore (portal=0x204661c) at pquery.c:937
#25 0x00186fac in PortalRun (portal=0x204661c, count=2147483647,  
dest=0x2031d4c, altdest=0x2031d4c, completionTag=0xbfffdc5a "") at  
#26 0x001823c8 in exec_simple_query (query_string=0x2031a1c "execute  
crash;") at postgres.c:939
#27 0x00183c54 in PostgresMain (argc=4, argv=0x201544c,  
username=0x2015424 "pfrost") at postgres.c:3424
#28 0x0015483c in ServerLoop () at postmaster.c:2931
#29 0x00155cf4 in PostmasterMain (argc=3, argv=0x1900750) at  
#30 0x001094b8 in main (argc=3, argv=0x1900780) at main.c:188

On Feb 14, 2007, at 10:13 PM, Tom Lane wrote:

> I wrote:
>> Hm, I see the assert failure, but this example doesn't seem to crash
>> when asserts are off, and I'd not expect it to: it should either  
>> work or
>> elog(ERROR) in ExecRestrPos.  So maybe you've found more than one  
>> issue.
> The attached patch fixes the failure you exhibited, but I still don't
> see how this problem would lead to a non-assert crash --- what you
> should get is elog(ERROR, "unrecognized node type") from ExecRestrPos.
> So please try some more test cases and see if there's another problem
> lurking.
> BTW, the problem was due to code added in response to an earlier  
> gripe of
> yours (allowing gating conditions to be pushed further down in the  
> join
> tree).  Maybe you're the only person stressing that particular aspect
> of the planner ...
> 			regards, tom lane

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