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sys.statistics column "nils" always contains 0. Expected a positive value for columns that have one or more nils/NULLs #6331

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monetdb-team opened this issue Nov 30, 2020 · 0 comments

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@monetdb-team monetdb-team commented Nov 30, 2020

Date: 2017-06-01 19:02:33 +0200
From: Martin van Dinther <<martin.van.dinther>>
To: SQL devs <>
Version: 11.25.23 (Dec2016-SP5)

Last updated: 2018-03-29 16:44:25 +0200

Comment 25370

Date: 2017-06-01 19:02:33 +0200
From: Martin van Dinther <<martin.van.dinther>>

User-Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:53.0) Gecko/20100101 Firefox/53.0
Build Identifier:

It appears that column "nils" of sys.statistics always contains 0 after running ANALYSE on all columns of all tables of schemas: sys, tmp and profiler.
I expected that columns "nils" would contain the number of nils/NULLs found in the specific column.

Reproducible: Always

Steps to Reproduce:

  1. Run SQL commands:
    ANALYSE sys;
    ANALYSE tmp;
    ANALYSE profiler;
    SELECT * FROM sys.statistics WHERE nils <> 0.
    SELECT * FROM sys.statistics WHERE minval = 'nil' OR maxval = 'nil';
    SELECT * FROM sys.statistics WHERE (minval = 'nil' OR maxval = 'nil') AND nils <> 0;

Actual Results:

nils always contain 0 for all columns analyzed, although there are many columns which have 'nil' as minimum or maximum value.

Expected Results:

For columns that have NULLs/nils value, the number of occurences in that column.

Comment 25383

Date: 2017-06-20 11:28:37 +0200
From: MonetDB Mercurial Repository <>

Changeset b4f5f29a002f made by Sjoerd Mullender sjoerd@acm.org in the MonetDB repo, refers to this bug.

For complete details, see http//devmonetdborg/hg/MonetDB?cmd=changeset;node=b4f5f29a002f

Changeset description:

Fix BATselect comment so that it tells the truth; fix call to select for NIL.
This fixes bug #6331.

Comment 25390

Date: 2017-06-22 14:14:15 +0200
From: MonetDB Mercurial Repository <>

Changeset 567718e3de97 made by Martin van Dinther martin.van.dinther@monetdbsolutions.com in the MonetDB repo, refers to this bug.

For complete details, see http//devmonetdborg/hg/MonetDB?cmd=changeset;node=567718e3de97

Changeset description:

Add test and output files for bug #6331

Comment 26330

Date: 2018-03-29 16:44:25 +0200
From: MonetDB Mercurial Repository <>

Changeset 8920ec11dedc made by Martin van Dinther martin.van.dinther@monetdbsolutions.com in the MonetDB repo, refers to this bug.

For complete details, see https//devmonetdborg/hg/MonetDB?cmd=changeset;node=8920ec11dedc

Changeset description:

Fix memory leak reported on
http://monetdb.cwi.nl/testweb/web/showtestoutput.php?serial=66173:f34a57f73307&target=GNU-Fedora-x86_64-sanitize&module=sql&test=sql%2Ftest%2FBugTracker-2017%2Fstatistics_nils_not_eq_zero.Bug-6331&which=err
The leak is introduced recently via [https//devmonetdborg/hg/MonetDB?cmd=changeset;node=78237ac1720c](https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=https//devmonetdborg/hg/MonetDB?cmd=changeset;node=78237ac1720c) 
I also found and removed two unneccesary GDKfree() calls to pointers which are already NULL.
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