MongoDB string functions - different handling of NULL values ------------------------------------------------------------ Key: TEIID-3598 URL: https://issues.jboss.org/browse/TEIID-3598 Project: Teiid Issue Type: Bug Components: Misc. Connectors Affects Versions: 8.7.1.6_2 Reporter: Jan Stastny Assignee: Ramesh Reddy Teiid doesn't handle NULL values right in given functions when working with mongodb. * SUBSTRING(<column resolving to NULL>,2) ** query: {code:sql} SELECT INTKEY, STRINGNUM, SUBSTRING(STRINGNUM, 2) FROM BQT1.SmallA ORDER BY INTKEY {code} ** source query: {code:plain} {"$project": {{ "c_0" : "$INTKEY" , "c_1" : "$STRINGNUM" , "c_2" : { "$substr" : [ "$STRINGNUM" , { "$subtract" : [ 2 , 1]} , 4000]}}}} {code} ** problem: For row with NULL value in given column returns sth like: {code:plain}{ "_id" : ObjectId("534bf17516997a2a41000002"), "c_0" : 1, "c_1" : null, "c_2" : "" } {code}which results in "" as result for SUBSTRING(NULL, 2) which should return NULL instead * UCASE, LCASE (UPPER, LOWER) ** query: {code:sql} SELECT intkey, stringnum, LOWER(stringnum) AS LOWER FROM BQT1.SmallA ORDER BY intkey {code} ** source query: {code:plain} {"$project": {{ "c_0" : "$INTKEY" , "c_1" : "$STRINGNUM" , "c_2" : { "$toLower" : [ "$STRINGNUM"]}}}} {code} ** problem: For row with NULL value in given column returns sth like: {code:plain} { "_id" : ObjectId("534bf17516997a2a41000002"), "c_0" : 1, "c_1" : null, "c_2" : "" } {code} which results in "" as result for LCASE(NULL) which should return NULL instead