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Add num_nulls() and num_nonnulls() to count NULL arguments.

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An example use-case is "CHECK(num_nonnulls(a,b,c) = 1)" to assert that
exactly one of a,b,c isn't NULL.  The functions are variadic, so they
can also be pressed into service to count the number of null or nonnull
elements in an array.

Marko Tiikkaja, reviewed by Pavel Stehule
This commit is contained in:
Tom Lane 2016-02-04 23:03:10 -05:00
parent d0cd7bda97
commit 6819514fca
9 changed files with 347 additions and 8 deletions
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53
doc/src/sgml/func.sgml
View File

@ -182,7 +182,7 @@
</sect1>
<sect1 id="functions-comparison">
<title>Comparison Operators</title>
<title>Comparison Functions and Operators</title>
<indexterm zone="functions-comparison">
<primary>comparison</primary>
@ -190,11 +190,11 @@
</indexterm>
<para>
The usual comparison operators are available, shown in <xref
linkend="functions-comparison-table">.
The usual comparison operators are available, as shown in <xref
linkend="functions-comparison-op-table">.
</para>
<table id="functions-comparison-table">
<table id="functions-comparison-op-table">
<title>Comparison Operators</title>
<tgroup cols="2">
<thead>
@ -437,6 +437,49 @@
</para>
-->
<para>
Some comparison-related functions are also available, as shown in <xref
linkend="functions-comparison-func-table">.
</para>
<table id="functions-comparison-func-table">
<title>Comparison Functions</title>
<tgroup cols="4">
<thead>
<row>
<entry>Function</entry>
<entry>Description</entry>
<entry>Example</entry>
<entry>Example Result</entry>
</row>
</thead>
<tbody>
<row>
<entry>
<indexterm>
<primary>num_nonnulls</primary>
</indexterm>
<literal>num_nonnulls(VARIADIC "any")</literal>
</entry>
<entry>returns the number of non-NULL arguments</entry>
<entry><literal>num_nonnulls(1, NULL, 2)</literal></entry>
<entry><literal>2</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>num_nulls</primary>
</indexterm>
<literal>num_nulls(VARIADIC "any")</literal>
</entry>
<entry>returns the number of NULL arguments</entry>
<entry><literal>num_nulls(1, NULL, 2)</literal></entry>
<entry><literal>1</literal></entry>
</row>
</tbody>
</tgroup>
</table>
</sect1>
<sect1 id="functions-math">
@ -10389,7 +10432,7 @@ table2-mapping
</note>
<para>
The standard comparison operators shown in <xref
linkend="functions-comparison-table"> are available for
linkend="functions-comparison-op-table"> are available for
<type>jsonb</type>, but not for <type>json</type>. They follow the
ordering rules for B-tree operations outlined at <xref
linkend="json-indexing">.

121
src/backend/utils/adt/misc.c
View File

@ -44,6 +44,127 @@
#define atooid(x) ((Oid) strtoul((x), NULL, 10))
/*
* Common subroutine for num_nulls() and num_nonnulls().
* Returns TRUE if successful, FALSE if function should return NULL.
* If successful, total argument count and number of nulls are
* returned into *nargs and *nulls.
*/
static bool
count_nulls(FunctionCallInfo fcinfo,
int32 *nargs, int32 *nulls)
{
int32 count = 0;
int i;
/* Did we get a VARIADIC array argument, or separate arguments? */
if (get_fn_expr_variadic(fcinfo->flinfo))
{
ArrayType *arr;
int ndims,
nitems,
*dims;
bits8 *bitmap;
Assert(PG_NARGS() == 1);
/*
* If we get a null as VARIADIC array argument, we can't say anything
* useful about the number of elements, so return NULL. This behavior
* is consistent with other variadic functions - see concat_internal.
*/
if (PG_ARGISNULL(0))
return false;
/*
* Non-null argument had better be an array. We assume that any call
* context that could let get_fn_expr_variadic return true will have
* checked that a VARIADIC-labeled parameter actually is an array. So
* it should be okay to just Assert that it's an array rather than
* doing a full-fledged error check.
*/
Assert(OidIsValid(get_base_element_type(get_fn_expr_argtype(fcinfo->flinfo, 0))));
/* OK, safe to fetch the array value */
arr = PG_GETARG_ARRAYTYPE_P(0);
/* Count the array elements */
ndims = ARR_NDIM(arr);
dims = ARR_DIMS(arr);
nitems = ArrayGetNItems(ndims, dims);
/* Count those that are NULL */
bitmap = ARR_NULLBITMAP(arr);
if (bitmap)
{
int bitmask = 1;
for (i = 0; i < nitems; i++)
{
if ((*bitmap & bitmask) == 0)
count++;
bitmask <<= 1;
if (bitmask == 0x100)
{
bitmap++;
bitmask = 1;
}
}
}
*nargs = nitems;
*nulls = count;
}
else
{
/* Separate arguments, so just count 'em */
for (i = 0; i < PG_NARGS(); i++)
{
if (PG_ARGISNULL(i))
count++;
}
*nargs = PG_NARGS();
*nulls = count;
}
return true;
}
/*
* num_nulls()
* Count the number of NULL arguments
*/
Datum
pg_num_nulls(PG_FUNCTION_ARGS)
{
int32 nargs,
nulls;
if (!count_nulls(fcinfo, &nargs, &nulls))
PG_RETURN_NULL();
PG_RETURN_INT32(nulls);
}
/*
* num_nonnulls()
* Count the number of non-NULL arguments
*/
Datum
pg_num_nonnulls(PG_FUNCTION_ARGS)
{
int32 nargs,
nulls;
if (!count_nulls(fcinfo, &nargs, &nulls))
PG_RETURN_NULL();
PG_RETURN_INT32(nargs - nulls);
}
/*
* current_database()
* Expose the current database to the user

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201602031
#define CATALOG_VERSION_NO 201602041
#endif

6
src/include/catalog/pg_proc.h
View File

@ -686,6 +686,12 @@ DATA(insert OID = 422 ( hashinet PGNSP PGUID 12 1 0 0 0 f f f f t f i s 1 0
DESCR("hash");
DATA(insert OID = 432 ( hash_numeric PGNSP PGUID 12 1 0 0 0 f f f f t f i s 1 0 23 "1700" _null_ _null_ _null_ _null_ _null_ hash_numeric _null_ _null_ _null_ ));
DESCR("hash");
DATA(insert OID = 438 ( num_nulls PGNSP PGUID 12 1 0 2276 0 f f f f f f i s 1 0 23 "2276" "{2276}" "{v}" _null_ _null_ _null_ pg_num_nulls _null_ _null_ _null_ ));
DESCR("count the number of NULL arguments");
DATA(insert OID = 440 ( num_nonnulls PGNSP PGUID 12 1 0 2276 0 f f f f f f i s 1 0 23 "2276" "{2276}" "{v}" _null_ _null_ _null_ pg_num_nonnulls _null_ _null_ _null_ ));
DESCR("count the number of non-NULL arguments");
DATA(insert OID = 458 ( text_larger PGNSP PGUID 12 1 0 0 0 f f f f t f i s 2 0 25 "25 25" _null_ _null_ _null_ _null_ _null_ text_larger _null_ _null_ _null_ ));
DESCR("larger of two");
DATA(insert OID = 459 ( text_smaller PGNSP PGUID 12 1 0 0 0 f f f f t f i s 2 0 25 "25 25" _null_ _null_ _null_ _null_ _null_ text_smaller _null_ _null_ _null_ ));

2
src/include/utils/builtins.h
View File

@ -490,6 +490,8 @@ extern Datum pg_ls_dir(PG_FUNCTION_ARGS);
extern Datum pg_ls_dir_1arg(PG_FUNCTION_ARGS);
/* misc.c */
extern Datum pg_num_nulls(PG_FUNCTION_ARGS);
extern Datum pg_num_nonnulls(PG_FUNCTION_ARGS);
extern Datum current_database(PG_FUNCTION_ARGS);
extern Datum current_query(PG_FUNCTION_ARGS);
extern Datum pg_cancel_backend(PG_FUNCTION_ARGS);

135
src/test/regress/expected/misc_functions.out Normal file
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@ -0,0 +1,135 @@
--
-- num_nulls()
--
SELECT num_nonnulls(NULL);
num_nonnulls
--------------
0
(1 row)
SELECT num_nonnulls('1');
num_nonnulls
--------------
1
(1 row)
SELECT num_nonnulls(NULL::text);
num_nonnulls
--------------
0
(1 row)
SELECT num_nonnulls(NULL::text, NULL::int);
num_nonnulls
--------------
0
(1 row)
SELECT num_nonnulls(1, 2, NULL::text, NULL::point, '', int8 '9', 1.0 / NULL);
num_nonnulls
--------------
4
(1 row)
SELECT num_nonnulls(VARIADIC '{1,2,NULL,3}'::int[]);
num_nonnulls
--------------
3
(1 row)
SELECT num_nonnulls(VARIADIC '{"1","2","3","4"}'::text[]);
num_nonnulls
--------------
4
(1 row)
SELECT num_nonnulls(VARIADIC ARRAY(SELECT CASE WHEN i <> 40 THEN i END FROM generate_series(1, 100) i));
num_nonnulls
--------------
99
(1 row)
SELECT num_nulls(NULL);
num_nulls
-----------
1
(1 row)
SELECT num_nulls('1');
num_nulls
-----------
0
(1 row)
SELECT num_nulls(NULL::text);
num_nulls
-----------
1
(1 row)
SELECT num_nulls(NULL::text, NULL::int);
num_nulls
-----------
2
(1 row)
SELECT num_nulls(1, 2, NULL::text, NULL::point, '', int8 '9', 1.0 / NULL);
num_nulls
-----------
3
(1 row)
SELECT num_nulls(VARIADIC '{1,2,NULL,3}'::int[]);
num_nulls
-----------
1
(1 row)
SELECT num_nulls(VARIADIC '{"1","2","3","4"}'::text[]);
num_nulls
-----------
0
(1 row)
SELECT num_nulls(VARIADIC ARRAY(SELECT CASE WHEN i <> 40 THEN i END FROM generate_series(1, 100) i));
num_nulls
-----------
1
(1 row)
-- special cases
SELECT num_nonnulls(VARIADIC NULL::text[]);
num_nonnulls
--------------
(1 row)
SELECT num_nonnulls(VARIADIC '{}'::int[]);
num_nonnulls
--------------
0
(1 row)
SELECT num_nulls(VARIADIC NULL::text[]);
num_nulls
-----------
(1 row)
SELECT num_nulls(VARIADIC '{}'::int[]);
num_nulls
-----------
0
(1 row)
-- should fail, one or more arguments is required
SELECT num_nonnulls();
ERROR: function num_nonnulls() does not exist
LINE 1: SELECT num_nonnulls();
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
SELECT num_nulls();
ERROR: function num_nulls() does not exist
LINE 1: SELECT num_nulls();
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.

2
src/test/regress/parallel_schedule
View File

@ -89,7 +89,7 @@ test: brin gin gist spgist privileges security_label collate matview lock replic
# ----------
# Another group of parallel tests
# ----------
test: alter_generic alter_operator misc psql async dbsize
test: alter_generic alter_operator misc psql async dbsize misc_functions
# rules cannot run concurrently with any test that creates a view
test: rules

1
src/test/regress/serial_schedule
View File

@ -119,6 +119,7 @@ test: misc
test: psql
test: async
test: dbsize
test: misc_functions
test: rules
test: select_views
test: portals_p2

31
src/test/regress/sql/misc_functions.sql Normal file
View File

@ -0,0 +1,31 @@
--
-- num_nulls()
--
SELECT num_nonnulls(NULL);
SELECT num_nonnulls('1');
SELECT num_nonnulls(NULL::text);
SELECT num_nonnulls(NULL::text, NULL::int);
SELECT num_nonnulls(1, 2, NULL::text, NULL::point, '', int8 '9', 1.0 / NULL);
SELECT num_nonnulls(VARIADIC '{1,2,NULL,3}'::int[]);
SELECT num_nonnulls(VARIADIC '{"1","2","3","4"}'::text[]);
SELECT num_nonnulls(VARIADIC ARRAY(SELECT CASE WHEN i <> 40 THEN i END FROM generate_series(1, 100) i));
SELECT num_nulls(NULL);
SELECT num_nulls('1');
SELECT num_nulls(NULL::text);
SELECT num_nulls(NULL::text, NULL::int);
SELECT num_nulls(1, 2, NULL::text, NULL::point, '', int8 '9', 1.0 / NULL);
SELECT num_nulls(VARIADIC '{1,2,NULL,3}'::int[]);
SELECT num_nulls(VARIADIC '{"1","2","3","4"}'::text[]);
SELECT num_nulls(VARIADIC ARRAY(SELECT CASE WHEN i <> 40 THEN i END FROM generate_series(1, 100) i));
-- special cases
SELECT num_nonnulls(VARIADIC NULL::text[]);
SELECT num_nonnulls(VARIADIC '{}'::int[]);
SELECT num_nulls(VARIADIC NULL::text[]);
SELECT num_nulls(VARIADIC '{}'::int[]);
-- should fail, one or more arguments is required
SELECT num_nonnulls();
SELECT num_nulls();