Bug#18761: constant expression as UDF parameters not passed in as constant

The code that set up data to be passed to user-defined functions was very
old and analyzed the "Type" of the data that was passed into the UDF, when
it really should analyze the "return_type", which is hard-coded for simple
Items and works correctly for complex ones like functions.
---
Added test at Sergei's behest.


mysql-test/r/udf.result:
  Verify that various arguments work.
  ---
  Added test at Sergei's behest.
mysql-test/t/udf.test:
  Verify that various arguments work.
  ---
  Added test at Sergei's behest.
sql/item_func.cc:
  For function-Items, test whether it is constant and set the struct members 
  for the UDF parameter appropriately.
  
  Replace tabs with spaces in affected code.
sql/udf_example.c:
  Include a simple function that is useful in testing.

1 files changed, 35 insertions, 0 deletions

diff --git a/mysql-test/r/udf.result b/mysql-test/r/udf.result
index 8e37cca6aa9..8501b82fcdf 100644
--- a/mysql-test/r/udf.result
+++ b/mysql-test/r/udf.result
@@ -115,3 +115,38 @@ DROP FUNCTION sequence;
 DROP FUNCTION lookup;
 DROP FUNCTION reverse_lookup;
 DROP FUNCTION avgcost;
+CREATE FUNCTION is_const RETURNS STRING SONAME "UDF_EXAMPLE_LIB";
+select
+is_const(3) as const,
+is_const(3.14) as const,
+is_const('fnord') as const,
+is_const(2+3) as const,
+is_const(rand()) as 'nc rand()',
+is_const(sin(3.14)) as const,
+is_const(upper('test')) as const;
+const	const	const	const	nc rand()	const	const
+const	const	const	const	not const	const	const
+create table bug18761 (n int);
+insert into bug18761 values (null),(2);
+select
+is_const(3) as const,
+is_const(3.14) as const,
+is_const('fnord') as const,
+is_const(2+3) as const,
+is_const(2+n) as 'nc  2+n  ',
+is_const(sin(n)) as 'nc sin(n)',
+is_const(sin(3.14)) as const,
+is_const(upper('test')) as const,
+is_const(rand()) as 'nc rand()',
+is_const(n) as 'nc   n   ',
+is_const(is_const(n)) as 'nc ic?(n)',
+is_const(is_const('c')) as const
+from
+bug18761;
+const	const	const	const	nc  2+n  	nc sin(n)	const	const	nc rand()	nc   n   	nc ic?(n)	const
+const	const	const	const	not const	not const	const	const	not const	not const	not const	const
+const	const	const	const	not const	not const	const	const	not const	not const	not const	const
+drop table bug18761;
+select is_const((1,2,3));
+ERROR 21000: Operand should contain 1 column(s)
+drop function if exists is_const;