Csc 1302, Honors Principles of Computer Science II (Fall 2021)

Week 9-14 (22 October 2021 to end of semester)

Relational Algebra Query Interpreter

For the rest of the semester you will build a Relational Algebra Query Interpreter using ANTLR4. Here is the grammar for Relational Algebra Queries:

query : expr SEMI

expr :
    factor UNION expr
  | factor MINUS expr
  | factor INTERSECT expr
  | factor

factor :
    term TIMES expr
  | term JOIN expr
  | term


term :
    NAME 
  | PROJECT LBRACKET alist RBRACKET LPAREN expr RPAREN
  | RENAME  LBRACKET alist RBRACKET LPAREN expr RPAREN
  | SELECT LBRACKET condition RBRACKET LPAREN expr RPAREN
  | LPAREN expr RPAREN

alist :
    NAME
  | alist COMMA NAME

condition :
    simplecondition
  | condition AND simplecondition 

simplecondition :
    operand COMPARISON operand

operand :
    NAME
  | STRING
  | NUMBER

fragment VALID_NAME_START : ('a'..'z') | ('A'..'Z');
fragment VALID_NAME_CHAR : VALID_NAME_START | ('0'..'9') | '_';
LBRACKET   : '[';
RBRACKET   : ']';
LPAREN     : '(';
RPAREN     : ')';
SEMI       : ';';
COMMA      : ',';
UNION      : 'UNION' | 'union';
MINUS      : 'MINUS' | 'minus';
INTERSECT  : 'INTERSECT' | 'intersect';
TIMES      : 'TIMES' | 'times';
JOIN       : 'JOIN' | 'join';
PROJECT    : 'PROJECT' | 'project';
SELECT     : 'SELECT' | 'select';
RENAME     : 'RENAME' | 'rename';
AND        : 'AND' | 'and';
NUMBER     : ('0'..'9')+ | ('0'..'9')* '.' ('0'..'9')+;
STRING     : '\'' (~[\r\n'] | '\'\'')* '\'';
COMPARISON : '< | '< | '>' | '>=' | '=' | '<>';
NAME       : VALID_NAME_START VALID_NAME_CHAR*;
WS         : [ \r\n\t]+ -> skip;

Download the files and implement the following 3 methods in RANode.java:

  public String semanticCheckAndSetSchemaAndDataTypes(Database db) {
    // Task 1: check for semantic errors; if error return error message
    //         otherwise return "OK"
    // Task 2: set values for the following three variables:
    //           public ArrayList joinColumns; // used to remember JOIN columns
    //           public ArrayList<String> schemaColumns;
    //           public ArrayList<String> schemaDataTypes;
  }

  public void setRelationNames(AtomicInteger globalInt) {
    // set unique relation names for every interior node in the tree
    //   public String relationName; // used to name interior nodes with tempN; relation name at leaf
  }

  public Relation evaluate(Database db) {
    // evaluate and return relation object for node
  }