Hive 3.1 基于代价的优化的判断条件

有四个必须条件需要同时满足。

1. 根节点的类型是一个 query，或者 explain，或者 create table as select，或者 materializedView。
2. 操作类型的判断条件：根节点的类型是 query，或者 create table as select，或者 materializedView；或者操作是 insert，或者多路 insert。
3. 不包含以下关键字：
4. canHandleQbForCbo 返回 null。

boolean canCBOHandleAst(ASTNode ast, QB qb, PreCboCtx cboCtx) {
    int root = ast.getToken().getType();
    boolean needToLogMessage = STATIC_LOG.isInfoEnabled();
    boolean isSupportedRoot = root == HiveParser.TOK_QUERY || root == HiveParser.TOK_EXPLAIN
        || qb.isCTAS() || qb.isMaterializedView();
    // Queries without a source table currently are not supported by CBO
    boolean isSupportedType = (qb.getIsQuery())
        || qb.isCTAS() || qb.isMaterializedView() || cboCtx.type == PreCboCtx.Type.INSERT
        || cboCtx.type == PreCboCtx.Type.MULTI_INSERT;
    boolean noBadTokens = HiveCalciteUtil.validateASTForUnsupportedTokens(ast);
    boolean result = isSupportedRoot && isSupportedType && noBadTokens;

    if (!result) {
      if (needToLogMessage) {
        String msg = "";
        if (!isSupportedRoot) {
          msg += "doesn't have QUERY or EXPLAIN as root and not a CTAS; ";
        }
        if (!isSupportedType) {
          msg += "is not a query with at least one source table "
                  + " or there is a subquery without a source table, or CTAS, or insert; ";
        }
        if (!noBadTokens) {
          msg += "has unsupported tokens; ";
        }

        if (msg.isEmpty()) {
          msg += "has some unspecified limitations; ";
        }
        STATIC_LOG.info("Not invoking CBO because the statement "
            + msg.substring(0, msg.length() - 2));
      }
      return false;
    }
    // Now check QB in more detail. canHandleQbForCbo returns null if query can
    // be handled.
    String msg = CalcitePlanner.canHandleQbForCbo(queryProperties, conf, true, needToLogMessage, qb);
    if (msg == null) {
      return true;
    }
    if (needToLogMessage) {
      STATIC_LOG.info("Not invoking CBO because the statement "
          + msg.substring(0, msg.length() - 2));
    }
    return false;

 public static boolean validateASTForUnsupportedTokens(ASTNode ast) {
    if (ParseUtils.containsTokenOfType(ast, HiveParser.TOK_CHARSETLITERAL, HiveParser.TOK_TABLESPLITSAMPLE)) {
      return false;
    } else {
      return true;
    }
  }

static String canHandleQbForCbo(QueryProperties queryProperties, HiveConf conf,
      boolean topLevelQB, boolean verbose, QB qb) {

    if (!queryProperties.hasClusterBy() && !queryProperties.hasDistributeBy()
        && !queryProperties.hasSortBy() && !queryProperties.hasPTF() && !queryProperties.usesscript()
        && queryProperties.isCBOSupportedLateralViews()) {
      // Ok to run CBO.
      return null;
    }

    // Not ok to run CBO, build error message.
    String msg = "";
    if (verbose) {
      if (queryProperties.hasClusterBy())
        msg += "has cluster by; ";
      if (queryProperties.hasDistributeBy())
        msg += "has distribute by; ";
      if (queryProperties.hasSortBy())
        msg += "has sort by; ";
      if (queryProperties.hasPTF())
        msg += "has PTF; ";
      if (queryProperties.usesscript())
        msg += "uses scripts; ";
      if (queryProperties.hasLateralViews())
        msg += "has lateral views; ";

      if (msg.isEmpty())
        msg += "has some unspecified limitations; ";
    }
    return msg;
  }