Added support for sys.fn_varbintohexsubstring function (#3659)

This PR adds full support for sys.fn_varbintohexsubstring function, addressing a current limitation in Babelfish. The implementation includes essential system function sys.fn_varbintohexsubstring required for comprehensive login export capabilities. This function in Babelfish is built maintaining compatibility with TSQL syntax.

Added Components

Function:

sys.fn_varbintohexsubstring: converts varbinary data to a hexadecimal string representation, optionally prefixed with '0x', with control over the starting position and length.

BABEL-5654

Signed-off-by: Shreya Rai shreyaxr@amazon.com

Author: shreyeah38

contrib/babelfishpg_tsql/sql/sys_functions.sql

@@ -4208,14 +4208,40 @@ BEGIN
 END; 
 $$ LANGUAGE plpgsql STABLE;
 
-CREATE OR REPLACE FUNCTION sys.fn_varbintohexsubstring(set_prefix INT, expression sys.varbinary(128), start_offset INT, length_to_return INT) 
-RETURNS sys.nvarchar(128) 
-AS $$ 
+CREATE OR REPLACE FUNCTION sys.fn_varbintohexsubstring(set_prefix sys.BIT, expression sys.varbinary, start_offset INT, substr_length INT)
+RETURNS sys.nvarchar AS 
+$$ 
 DECLARE 
+    pstrout sys.nvarchar;
+    hex_str text;
 BEGIN 
-    RETURN NULL; 
-END; 
-$$ LANGUAGE plpgsql STABLE;
+    IF expression IS NULL THEN 
+        RETURN NULL;
+    END IF;
+
+    IF substr_length IS NULL OR substr_length <= 0 OR substr_length > sys.LEN(expression) THEN 
+        substr_length := sys.LEN(expression);
+    END IF;
+
+    IF start_offset IS NULL OR start_offset < 1 OR start_offset > sys.LEN(expression) THEN 
+        RETURN NULL;
+    END IF;
+
+    IF (sys.LEN(expression) - start_offset + 1) < substr_length THEN 
+        substr_length := sys.LEN(expression) - start_offset + 1;
+    END IF;
+
+    hex_str := sys.LOWER(pg_catalog.ENCODE(sys.SUBSTRING(expression, start_offset, substr_length)::bytea, 'hex'));
+    
+    pstrout := CASE 
+                WHEN set_prefix IS NULL THEN N''
+                WHEN set_prefix = 0 THEN N'' 
+                ELSE N'0x' 
+               END || hex_str;
+    RETURN pstrout;
+END;
+$$ 
+LANGUAGE plpgsql IMMUTABLE;
 
 CREATE OR REPLACE FUNCTION objectproperty(
     id INT,

contrib/babelfishpg_tsql/sql/upgrades/babelfishpg_tsql--4.5.0--4.6.0.sql

@@ -1860,14 +1860,40 @@ BEGIN
 END; 
 $$ LANGUAGE plpgsql STABLE;
 
-CREATE OR REPLACE FUNCTION sys.fn_varbintohexsubstring(set_prefix INT, expression sys.varbinary(128), start_offset INT, length_to_return INT) 
-RETURNS sys.nvarchar(128) 
-AS $$ 
+CREATE OR REPLACE FUNCTION sys.fn_varbintohexsubstring(set_prefix sys.BIT, expression sys.varbinary, start_offset INT, substr_length INT)
+RETURNS sys.nvarchar AS 
+$$ 
 DECLARE 
+    pstrout sys.nvarchar;
+    hex_str text;
 BEGIN 
-    RETURN NULL; 
-END; 
-$$ LANGUAGE plpgsql STABLE;
+    IF expression IS NULL THEN 
+        RETURN NULL;
+    END IF;
+
+    IF substr_length IS NULL OR substr_length <= 0 OR substr_length > sys.LEN(expression) THEN 
+        substr_length := sys.LEN(expression);
+    END IF;
+
+    IF start_offset IS NULL OR start_offset < 1 OR start_offset > sys.LEN(expression) THEN 
+        RETURN NULL;
+    END IF;
+
+    IF (sys.LEN(expression) - start_offset + 1) < substr_length THEN 
+        substr_length := sys.LEN(expression) - start_offset + 1;
+    END IF;
+
+    hex_str := sys.LOWER(pg_catalog.ENCODE(sys.SUBSTRING(expression, start_offset, substr_length)::bytea, 'hex'));
+    
+    pstrout := CASE 
+                WHEN set_prefix IS NULL THEN N''
+                WHEN set_prefix = 0 THEN N'' 
+                ELSE N'0x' 
+               END || hex_str;
+    RETURN pstrout;
+END;
+$$ 
+LANGUAGE plpgsql IMMUTABLE;
 
 CREATE OR REPLACE VIEW sys.server_permissions AS 
 WITH super_user AS (SELECT datdba AS super_user FROM pg_database WHERE datname = CURRENT_DATABASE()) 

test/JDBC/expected/sys-fn-varbintohexsubstring-vu-cleanup.out

@@ -6,3 +6,24 @@ GO
 
 DROP FUNCTION fn_varbintohexsubstring_vu_prepare_func
 GO
+
+DROP TABLE babel_5654_t1
+GO
+
+DROP TABLE babel_5654_t2
+GO
+
+DROP TABLE babel_5654_t3
+GO
+
+DROP TYPE SetPrefixType
+GO
+
+DROP TYPE ExpressionType
+GO
+
+DROP TYPE StartOffsetType
+GO
+
+DROP TYPE SubstrLengthType
+GO

test/JDBC/expected/sys-fn-varbintohexsubstring-vu-prepare.out

@@ -1,16 +1,65 @@
 -- Create dependant objects
 CREATE VIEW fn_varbintohexsubstring_vu_prepare_view AS
-SELECT sys.fn_varbintohexsubstring(1, CAST('0x1234' AS varbinary(128)), 1, 4)
+SELECT sys.fn_varbintohexsubstring(1,0x1234, 1, 4)
 GO
 
 CREATE PROC fn_varbintohexsubstring_vu_prepare_proc AS
-SELECT sys.fn_varbintohexsubstring(1, CAST('0x1234' AS varbinary(128)), 1, 4)
+SELECT sys.fn_varbintohexsubstring(1,0x1234, 1, 4)
 GO
 
 CREATE FUNCTION fn_varbintohexsubstring_vu_prepare_func()
 RETURNS nvarchar(128)
 AS
 BEGIN
-RETURN sys.fn_varbintohexsubstring(1, CAST('0x1234' AS varbinary(128)), 1, 4)
+RETURN sys.fn_varbintohexsubstring(1,0x1234, 1, 4)
 END
 GO
+
+CREATE TABLE babel_5654_t1 (set_prefix sys.BIT,
+                            expression sys.varbinary(MAX),
+                            start_offset INT,
+                            substr_length INT,
+                            CHECK (sys.fn_varbintohexsubstring(set_prefix, expression, start_offset, substr_length) != NULL));
+GO
+
+INSERT INTO babel_5654_t1 VALUES (0,0x123486534659789876435656,1,4)
+GO
+~~ROW COUNT: 1~~
+
+
+CREATE TABLE babel_5654_t2 (set_prefix sys.BIT,
+                            expression sys.varbinary(MAX),
+                            start_offset INT,
+                            substr_length INT,
+                            [varbintohexsubstring] AS sys.fn_varbintohexsubstring(set_prefix, expression, start_offset, substr_length));
+GO
+
+INSERT INTO babel_5654_t2 VALUES (0,0x3486534659789876435656,1,4)
+GO
+~~ROW COUNT: 1~~
+
+
+CREATE TYPE SetPrefixType from sys.bit;
+GO
+
+CREATE TYPE ExpressionType from sys.varbinary(MAX);
+GO
+
+CREATE TYPE StartOffsetType from int;
+GO
+
+CREATE TYPE SubstrLengthType from int;
+GO
+
+CREATE TABLE babel_5654_t3 (set_prefix SetPrefixType,
+                            expression ExpressionType,
+                            start_offset StartOffsetType,
+                            substr_length SubstrLengthType,
+                            [varbintohexsubstring] AS sys.fn_varbintohexsubstring(set_prefix, expression, start_offset, substr_length));
+GO
+
+INSERT INTO babel_5654_t3 VALUES (0,0x3486534659789876435656,1,4)
+GO
+~~ROW COUNT: 1~~
+
+