[sqlsmith] Failed assertion in brin_minmax_multi_distance_float4 on REL_14_STABLE

Started by Andreas Seltenreichabout 4 years ago5 messages

Andreas Seltenreich

andreas.seltenreich@credativ.de

about 4 years ago

Hi,

sqlsmith triggers the following assertion when testing REL_14_STABLE:

TRAP: FailedAssertion("a1 <= a2", File: "brin_minmax_multi.c", Line: 1879, PID: 631814)

I can reproduce it with the following query on a fresh regression
database:

insert into public.brintest_multi (float4col) values (real 'nan');

The branch was at f6162c020c while testing, backtrace below.

regards,
Andreas

(gdb) bt
#0 0x00007f703cc46ce1 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007f703cc30537 in abort () from /lib/x86_64-linux-gnu/libc.so.6
#2 0x000055b17517c521 in ExceptionalCondition at assert.c:69
#3 0x000055b174d25871 in brin_minmax_multi_distance_float4 (fcinfo=<optimized out>) at brin_minmax_multi.c:1879
#4 0x000055b1751853ba in FunctionCall2Coll (flinfo=flinfo@entry=0x55b176913d10, collation=collation@entry=0, arg1=<optimized out>,
arg2=<optimized out>) at fmgr.c:1160
#5 0x000055b174d23a41 in build_distances (distanceFn=distanceFn@entry=0x55b176913d10, colloid=0,
eranges=eranges@entry=0x55b17693fad0, neranges=neranges@entry=5) at brin_minmax_multi.c:1352
#6 0x000055b174d256be in compactify_ranges (max_values=32, ranges=0x55b176945708, bdesc=<optimized out>) at brin_minmax_multi.c:1822
#7 brin_minmax_multi_serialize (bdesc=<optimized out>, src=94220687005448, dst=0x55b17693ae10) at brin_minmax_multi.c:2386
#8 0x000055b174d2ae0d in brin_form_tuple (brdesc=brdesc@entry=0x55b176914988, blkno=blkno@entry=15,
tuple=tuple@entry=0x55b17693aaa0, size=size@entry=0x7ffffcc6d4f8) at brin_tuple.c:165
#9 0x000055b174d20a5f in brininsert (idxRel=0x7f703b2ae170, values=0x7ffffcc6d610, nulls=0x7ffffcc6d5f0, heaptid=0x55b17690da78,

Justin Pryzby

pryzby@telsasoft.com

about 4 years ago

In reply to: Andreas Seltenreich (#1)

Re: [sqlsmith] Failed assertion in brin_minmax_multi_distance_float4 on REL_14_STABLE

On Thu, Nov 04, 2021 at 09:46:49AM +0100, Andreas Seltenreich wrote:

sqlsmith triggers the following assertion when testing REL_14_STABLE:

TRAP: FailedAssertion("a1 <= a2", File: "brin_minmax_multi.c", Line: 1879, PID: 631814)

I can reproduce it with the following query on a fresh regression
database:

insert into public.brintest_multi (float4col) values (real 'nan');

The branch was at f6162c020c while testing, backtrace below.

I couldn't reproduce this, but it reminds me of this one, which we also had
trouble reproducing.

/messages/by-id/20210913004447.GA17931@ahch-to

Could you send a "bt full" ?

(gdb) bt

--
Justin

Tomas Vondra

tomas.vondra@enterprisedb.com

about 4 years ago

In reply to: Justin Pryzby (#2)

Re: [sqlsmith] Failed assertion in brin_minmax_multi_distance_float4 on REL_14_STABLE

Hi,

On 11/4/21 17:53, Justin Pryzby wrote:

On Thu, Nov 04, 2021 at 09:46:49AM +0100, Andreas Seltenreich wrote:

sqlsmith triggers the following assertion when testing REL_14_STABLE:

TRAP: FailedAssertion("a1 <= a2", File: "brin_minmax_multi.c", Line: 1879, PID: 631814)

I can reproduce it with the following query on a fresh regression
database:

insert into public.brintest_multi (float4col) values (real 'nan');

The branch was at f6162c020c while testing, backtrace below.

I couldn't reproduce this, but it reminds me of this one, which we also had
trouble reproducing.

I can reproduce that just fine - all I had to do was 'make installcheck'
and then connect to the regression db and run the insert.

It seems to be a simple case of confusion in handling of NaN values. We
do sort them correctly (by calling float4_lt), but given two values

arg1 = nan (0x400000)
arg2 = 0.0909090936

then a simple comparison does not give the expected result

(arg1 < arg2)
(arg1 == arg2)
(arg1 > arg2)

all evaluate to false, which is why the assert fails. So I guess the
distance function for float4 (and probably float8 too) need a couple
more lines checking NaN.

regards

--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Tomas Vondra

tomas.vondra@enterprisedb.com

about 4 years ago

In reply to: Tomas Vondra (#3)

Re: [sqlsmith] Failed assertion in brin_minmax_multi_distance_float4 on REL_14_STABLE

On 11/4/21 23:56, Tomas Vondra wrote:

Hi,

On 11/4/21 17:53, Justin Pryzby wrote:

On Thu, Nov 04, 2021 at 09:46:49AM +0100, Andreas Seltenreich wrote:

sqlsmith triggers the following assertion when testing REL_14_STABLE:

TRAP: FailedAssertion("a1 <= a2", File: "brin_minmax_multi.c",
Line: 1879, PID: 631814)

I can reproduce it with the following query on a fresh regression
database:

insert into public.brintest_multi (float4col) values (real 'nan');

The branch was at f6162c020c while testing, backtrace below.

I couldn't reproduce this, but it reminds me of this one, which we
also had
trouble reproducing.

I can reproduce that just fine - all I had to do was 'make installcheck'
and then connect to the regression db and run the insert.

It seems to be a simple case of confusion in handling of NaN values. We
do sort them correctly (by calling float4_lt), but given two values

arg1 = nan (0x400000)
arg2 = 0.0909090936

then a simple comparison does not give the expected result

(arg1 < arg2)
(arg1 == arg2)
(arg1 > arg2)

all evaluate to false, which is why the assert fails. So I guess the
distance function for float4 (and probably float8 too) need a couple
more lines checking NaN.

Here's a patch that should fix this. It simply handled NaN and returns
distance 0.0 for two NaN values and Infinity for NaN vs. something else.
I did check what happens with Infinity values, but I think those are
fine - we can actually calculate distance with them, and the assert
works for them too.

I'll improve the regression tests to include a couple NaN/Infinity cases
tomorrow, and then I'll get this pushed.

regards

--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Tomas Vondra

tomas.vondra@enterprisedb.com

about 4 years ago

In reply to: Tomas Vondra (#4)

1 attachment(s)

Re: [sqlsmith] Failed assertion in brin_minmax_multi_distance_float4 on REL_14_STABLE

On 11/5/21 02:09, Tomas Vondra wrote:

Here's a patch that should fix this.

Meh, forgot the attachment, ofc.

--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Attachments:

brin-fix.patchtext/x-patch; charset=UTF-8; name=brin-fix.patchDownload

diff --git a/src/backend/access/brin/brin_minmax_multi.c b/src/backend/access/brin/brin_minmax_multi.c
index ee6c4795f1..a85dfdfec4 100644
--- a/src/backend/access/brin/brin_minmax_multi.c
+++ b/src/backend/access/brin/brin_minmax_multi.c
@@ -73,6 +73,7 @@
 #include "utils/builtins.h"
 #include "utils/date.h"
 #include "utils/datum.h"
+#include "utils/float.h"
 #include "utils/inet.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
@@ -1872,6 +1873,14 @@ brin_minmax_multi_distance_float4(PG_FUNCTION_ARGS)
 	float		a1 = PG_GETARG_FLOAT4(0);
 	float		a2 = PG_GETARG_FLOAT4(1);
 
+	/* if both values are NaN, then we consider them the same */
+	if (isnan(a1) && isnan(a2))
+		PG_RETURN_FLOAT8(0.0);
+
+	/* if one value is NaN, use infinite distance */
+	if (isnan(a1) || isnan(a2))
+		PG_RETURN_FLOAT8(get_float8_infinity());
+
 	/*
 	 * We know the values are range boundaries, but the range may be collapsed
 	 * (i.e. single points), with equal values.
@@ -1890,6 +1899,14 @@ brin_minmax_multi_distance_float8(PG_FUNCTION_ARGS)
 	double		a1 = PG_GETARG_FLOAT8(0);
 	double		a2 = PG_GETARG_FLOAT8(1);
 
+	/* if both values are NaN, then we consider them the same */
+	if (isnan(a1) && isnan(a2))
+		PG_RETURN_FLOAT8(0.0);
+
+	/* if one value is NaN, use infinite distance */
+	if (isnan(a1) || isnan(a2))
+		PG_RETURN_FLOAT8(get_float8_infinity());
+
 	/*
 	 * We know the values are range boundaries, but the range may be collapsed
 	 * (i.e. single points), with equal values.