protected Map<ASTNode, T> genExprNode(ASTNode expr, TypeCheckCtx tcCtx) throws SemanticException {
    // Create the walker, the rules dispatcher and the context.
    // create a walker which walks the tree in a DFS manner while maintaining
    // the operator stack. The dispatcher
    // generates the plan from the operator tree

    SetMultimap<Integer, SemanticNodeProcessor> astNodeToProcessor = HashMultimap.create();
    astNodeToProcessor.put(HiveParser.TOK_NULL, getNullExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_PARAMETER, getDynamicParameterProcessor());
    astNodeToProcessor.put(HiveParser.Number, getNumExprProcessor());
    astNodeToProcessor.put(HiveParser.IntegralLiteral, getNumExprProcessor());
    astNodeToProcessor.put(HiveParser.NumberLiteral, getNumExprProcessor());

    astNodeToProcessor.put(HiveParser.Identifier, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.StringLiteral, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_CHARSETLITERAL, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_STRINGLITERALSEQUENCE, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_IF, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_CASE, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_WHEN, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_IN, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_ARRAY, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_MAP, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_STRUCT, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_EXISTS, getStrExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_SUBQUERY_OP_NOTIN, getStrExprProcessor());

    astNodeToProcessor.put(HiveParser.KW_TRUE, getBoolExprProcessor());
    astNodeToProcessor.put(HiveParser.KW_FALSE, getBoolExprProcessor());

    astNodeToProcessor.put(HiveParser.TOK_DATELITERAL, getDateTimeExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_TIMESTAMPLITERAL, getDateTimeExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_TIMESTAMPLOCALTZLITERAL, getDateTimeExprProcessor());

    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_YEAR_MONTH_LITERAL, getIntervalExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_DAY_TIME_LITERAL, getIntervalExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_YEAR_LITERAL, getIntervalExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_MONTH_LITERAL, getIntervalExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_DAY_LITERAL, getIntervalExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_HOUR_LITERAL, getIntervalExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_MINUTE_LITERAL, getIntervalExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_INTERVAL_SECOND_LITERAL, getIntervalExprProcessor());

    astNodeToProcessor.put(HiveParser.TOK_TABLE_OR_COL, getColumnExprProcessor());

    astNodeToProcessor.put(HiveParser.TOK_SUBQUERY_EXPR, getSubQueryExprProcessor());
    astNodeToProcessor.put(HiveParser.TOK_ALIAS, getValueAliasProcessor());

    // The dispatcher fires the processor corresponding to the closest matching
    // rule and passes the context along
    SemanticDispatcher disp = new CostLessRuleDispatcher(getDefaultExprProcessor(),
        astNodeToProcessor, tcCtx);
    SemanticGraphWalker ogw = new SubqueryExpressionWalker(disp);

    // Create a list of top nodes
    ArrayList<Node> topNodes = Lists.<Node>newArrayList(expr);
    HashMap<Node, Object> nodeOutputs = new LinkedHashMap<Node, Object>();
    ogw.startWalking(topNodes, nodeOutputs);

    return convert(nodeOutputs);
  }
Factory that will be used to create the different expressions.
ql/src/java/org/apache/hadoop/hive/ql/parse/type/TypeCheckProcFactory.java