Re: additional details on IS NULL problem

Hi Lynn, here are the NIL/NULL values that MonetDB uses for 32-bit FLT (REAL) and 64-bit DBL (FLOAT/DOUBLE), respectively: $ cat x.c #include #include #include /* for FLT_MAX & DBL_MAX */ int main(void) { float f = -FLT_MAX; double d = -DBL_MAX; printf("flt_nil == -FLT_MAX == %g\n",f); printf("flt_nil == -FLT_MAX == %.999g\n",f); printf("dbl_nil == -DBL_MAX == %g\n",d); printf("dbl_nil == -DBL_MAX == %.999g\n",d); return 0; } $ gcc x.c -o x && ./x flt_nil == -FLT_MAX == -3.40282e+38 flt_nil == -FLT_MAX == -340282346638528859811704183484516925440 dbl_nil == -DBL_MAX == -1.79769e+308 dbl_nil == -DBL_MAX == -179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368 ----- On May 23, 2016, at 11:04 PM, Lynn Carol Johnson lcj34@cornell.edu wrote:

Update: I changed my missing values to be Float.MIN_VALUE instead of Float.NaN. This did not fix the problem. When they were Float.Nan, and loaded from binary, the data showed up as “NULL” when doing a select (though “count” did NOT seem to recognize this as null).

When these values are stored as Float.MIN_VALUE and loaded from binary files, they appear in the data base as 1.401e-45. This is correct as this is the value of Float.MIN_VALUE, but I had thought from reading the documentation that this would be translated to null.

When I export the data to a text file, then drop/reload the table from the text file, the values are still 1.401e-45, so neither IS NULL or IS NOT NULL work.

The table from your link shows “nil" should be “GDK_flt_min”. Is that value something other than Float.MIN_VALUE?

On 5/23/16, 4:30 PM, "users-list on behalf of Lynn Carol Johnson" wrote:

...

For this particular run, the null¹s were all from Float.NaN, so perhaps that is the problem.

My list-of-things-to-do includes checking if null works properly when using *.MIN_VALUE, as we are using that as well for int and byte. We have only recently changed our data to include ³null² as previously we had Spark issues so everything was given a numeric value.

I will run and let you know. It will be no problem to store Float.MIN_VALUE instead of Float.NaN

On 5/23/16, 4:06 PM, "users-list on behalf of Stefan Manegold" wrote:

...

Hi Lynn,

thanks for diving into this!

The information that you loaded your data using from binary files using copy *binary* into is crucial for us to understand and investigate the problem!

In fact, I recently discovered and fixed a similar bug; cf., https://www.monetdb.org/bugzilla/show_bug.cgi?id=3937

This fix is in the Jul2013-SP3 bug-fix release. Hence, I'm wondering why you (still) experience this (or a similar) problem.

Of what type are your data / columns? Integer? decimal? floating point? string?

If more then one type, do you experience these problems with all types or just with some? If only some, which?

If the problem occurs only with floating point numbers, are you sure you're using the exact NULL representation that MonetDB uses?

Otherwise a potential source of the problem --- I'm just speculating --- could be the following:

You might have "non-valid" floating point numbers like NaN or INF in your data that are not known to SQL and hence MonetDB. If so, When parsed from text, MonetDB does (seems to?) silently turn them into (MonetDB's internal representation of) NULL. However, when loding your binary data, MonetDB stores these values "as-is" not recognizing them as NULL; then processing does not recognize them as NULL, either; only rendering produces NULL from the "non-valid" internal representation.

For the correct internal representation of NULL values in MonetDB per type see https://www.monetdb.org/wiki/MonetDB_type_system

If my speculation is true, we'd need to consider making our copy binary into bulk-loading for floating point numbers (more) fail-save by actually scanning each column and checking for "invalid" floating point number --- whatever that might cost ...

Best, Stefan

----- On May 23, 2016, at 8:37 PM, Lynn Carol Johnson lcj34@cornell.edu wrote:

...

Hi Anthony -

I¹ve narrowed down the problem. The bug isn¹t related to size, but rather how the table data was created/loaded. Loading from a .txt file gives good behavior, loading from binary does not.

Normally I create binary files for each column and use the binary bulk loader to load. That is what was failing. When I first tested with 50 columns, I created the test file from sql via the command copy (select * Š) into Œ/workdir/ŠkellyFirst50.txt using delimiters Œ\t¹,¹\n¹;

Then I created a new table called kellyFirst50 and used the ³COPY INTO kellyfirst50 from Œ/workdirŠkellyFirst50.txt¹ using delimiters Œ\t,¹\n¹; ² command. Checking for ³IS NULL² worked, so I thought it was a size problem.

But, when trying to figure out at what point the file size mattered, I ran java scripts to create binary files of ever decreasing sizes, then loaded them via the COPY BINARY commands. Checking for IS NULL always failed here, even when I only loaded 50 values.

Here are the results when loading from binary files into monetdb. Using IS NOT NULL works, but IS NULL does not:

sql>\

operation successful

sql>\

50 affected rows

sql>

sql>select count(*) from weirtestnull;

+------+

| L1 |

+======+

| 50 |

+------+

1 tuple (2.014ms)

sql>select count(amesbyd_weir) from weirtestnull;

+------+

| L1 |

+======+

| 50 |

+------+

1 tuple (0.865ms)

sql>select count(amesbyd_weir) from weirtestnull where amesbyd_weir IS NOT NULL;

+------+

| L1 |

+======+

| 34 |

+------+

1 tuple (3.005ms)

sql>

sql>select * from weirtestnull where amesbyd_weir IS NULL;

+-----+-----+---------------+--------------+--------------+------------- - --+--------------------+------------------+----------------+

| chr | pos | amesbycn_weir | amesbyd_weir | amesbyf_weir | amesbynam_weir | | amesbyturkeyp_weir | dentbyflint_weir | dentbynam_weir |>

+=====+=====+===============+==============+==============+============= = ==+====================+==================+================+

+-----+-----+---------------+--------------+--------------+------------- - --+--------------------+------------------+----------------+

0 tuples (4.041ms) !4 columns dropped!

sql>

Dump the data into a .txt file:

sql>copy (select * from weirtestnull) into '/workdir/db_outfiles/weirtestnull.txt' using delimiters '\t','\n';

50 affected rows (3.809ms)

sql>

Now drop the table, recreate it, but this time load from the txt file created above:

sql>drop table weirtestnull;

operation successful (1.948ms)

sql>\

operation successful

sql>copy into weirtestnull from '/workdir/db_outfiles/weirtestnull.txt' using delimiters '\t','\n';

50 affected rows (57.643ms)

sql>

Re-run the commands ­ I now get correct values for IS NULL:

sql>select count(*) from weirtestnull;

+------+

| L1 |

+======+

| 50 |

+------+

1 tuple (1.851ms)

sql>select count(amesbyd_weir) from weirtestnull;

+------+

| L1 |

+======+

| 34 |

+------+

1 tuple (0.983ms)

sql>

sql>select * from weirtestnull where amesbyd_weir IS NULL;

+------+--------+------------+------------+------------+------------+--- - ---------+-------------+-------------+-------------+-------------+------ - ------+

| chr | pos | amesbycn_w | amesbyd_we | amesbyf_we | amesbynam_ | amesbyturke | | dentbyflint | dentbynam_w | dentbyturke | flintbynam_ | flintbyturk |>

: : : eir : ir : ir : weir : yp_weir : _weir : eir : ypen_weir : weir : eypen_weir :>

+======+========+============+============+============+============+=== = =========+=============+=============+=============+=============+====== = ======+

| 10 | 228864 | 2.95496e-0 | null | null | -0.0001263 | null | null | -0.00028749 | | null | -0.00029885 | null |

: : : 5 : : : 25 : : : 4 : : 1 : :

| 10 | 228962 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 228972 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229011 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229025 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229187 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229367 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229405 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229444 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229593 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229615 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229671 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 229829 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 230000 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 230052 | null | null | null | null | null | null | null | null | null | | null |

| 10 | 230120 | null | null | null | null | null | null | null | null | null | | null |

+------+--------+------------+------------+------------+------------+--- - ---------+-------------+-------------+-------------+-------------+------ - ------+

16 tuples (5.2

My java program uses Float.NaN and Integer.MIN_VALUE, Byte.MIN_VALUE to get ³null² stored in the db.

When we load directly from binary, are the null values created differently? Is something not marked that gets marked when loading from text files?

With this information, can you reproduce, or do you want me to give you my binary files in a dropbox somewhere?

Thanks - Lynn

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