Update SQL.js to fix head operations for pg engine.

Postgres requires the "length" function vs "len" function as some SQL engines us, this patch would add the correct wrapping in the getBlobSizefn

engines/SQL.js

@@ -85,7 +85,22 @@ module.exports = class SQLEngine extends Component {
         // some column name aliases to adjust to default DB case
         let CREATED = 'created'
         let UPDATED = 'updated'
-
+
+	/*Postgres requires "length" instead of len for bytea fields. Noticed failures during head operations. 
+	 The other option would be to create a postgres function called len() on setup create which wraps the length() operation.
+	 CREATE OR REPLACE FUNCTION len(byteafield bytea)
+	 RETURNS int AS
+	 $$
+	 BEGIN
+    		RETURN length(byteafield);
+	END;
+	$$
+	LANGUAGE plpgsql IMMUTABLE;
+	*/
+        if (this.client === 'pg'){
+		this.getBlobSizefn = "length(\"V\")"
+	}
+
         if (this.client === 'mssql') {
             this.getBlobSizeFn = 'len(V)'
             this.mergeStmt = `