Re: Extended Statistics set/restore/clear functions.

hi.

makeJsonLexContextCstringLen in v16-0001 and v16-0002
should use GetDatabaseEncoding()?

wondering, should we check the value of "degree" is between 0 to 1?

+ if ((natts < 1) || (natts > (STATS_MAX_DIMENSIONS - 1)))
+ {
+ errsave(parse->escontext,
+ errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+ errmsg("malformed pg_dependencies: \"%s\"", parse->str),
+ errdetail("The \"%s\" key must contain an array of at least %d "
+ " and no than %d elements.",
+ PG_DEPENDENCIES_KEY_ATTRIBUTES, 1, STATS_MAX_DIMENSIONS - 1));

DETAIL: The "attributes" key must contain an array of at least 1 and
no than 7 elements.
if you check the error message carefully, there is one more extra
white space after "at least 1".

typedef struct MVDependency
{
double degree; /* degree of validity (0-1) */
AttrNumber nattributes; /* number of attributes */
AttrNumber attributes[FLEXIBLE_ARRAY_MEMBER]; /* attribute numbers */
} MVDependency;

SELECT '[{"attributes" : [2], "dependency" : 4, "degree":
"NaN"}]'::pg_dependencies;
SELECT '[{"attributes" : [2], "dependency" : 4, "degree":
"-inf"}]'::pg_dependencies;
SELECT '[{"attributes" : [2], "dependency" : 4, "degree":
"inf"}]'::pg_dependencies;

either error out or not, pg_dependencies.sql needs tests like the
above to test these special values.
json does not support special value like, "inf", "NaN", so we can
SELECT '[{"attributes" : [2], "dependency" : 4, "degree":
"-inf"}]'::pg_dependencies;
but can not
SELECT '[{"attributes" : [2], "dependency" : 4, "degree":
"-inf"}]'::pg_dependencies::text::pg_dependencies;

I found that numeric values behave the same with or without double quotes.
SELECT '[{"ndistinct" : "1", "attributes" : ["2","3"]}]'::pg_ndistinct;
SELECT '[{"ndistinct" : 1, "attributes" : [2,3]}]'::pg_ndistinct;
SELECT '[{"attributes" : [1, 2], "dependency" : 4, "degree":
"1"}]'::pg_dependencies;
SELECT '[{"attributes" : [1, "2"], "dependency" : "4", "degree":
"1"}]'::pg_dependencies;
i guess the reason is in makeJsonLexContextCstringLen, we set
need_escapes to true.

I added more regress tests to improve coverage for
src/test/regress/sql/pg_dependencies.sql

SELECT '[{"attributes" : [-11,1], "dependency" : -1116, "degree":
"1.2"}]'::pg_dependencies;
DETAIL: Invalid "attributes" element: -11.
we already check the key "attributes", we can also check "dependency",
IF the value of ""dependency"
does not meet
``(if (parse->dependency == 0 || parse->dependency < (0-STATS_MAX_DIMENSIONS))``
then error out.
see the attached patch.

--
jian
https://www.enterprisedb.com/