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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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package org.apache.impala.analysis;

import static org.apache.impala.analysis.ToSqlOptions.DEFAULT;

import java.util.ArrayList;
import java.util.List;

import org.apache.impala.authorization.PrivilegeRequest;
import org.apache.impala.catalog.FeView;
import org.apache.impala.catalog.View;
import org.apache.impala.common.AnalysisException;

import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;

/**
 * Representation of the WITH clause that may appear before a query statement or insert
 * statement. A WITH clause contains a list of named view definitions that may be
 * referenced in the query statement that follows it.
 *
 * Scoping rules:
 * A WITH-clause view is visible inside the query statement that it belongs to.
 * This includes inline views and nested WITH clauses inside the query statement.
 *
 * Each WITH clause establishes a new analysis scope. A WITH-clause view definition
 * may refer to views from the same WITH-clause appearing to its left, and to all
 * WITH-clause views from outer scopes.
 *
 * References to WITH-clause views are resolved inside out, i.e., a match is found by
 * first looking in the current scope and then in the enclosing scope(s).
 *
 * Views defined within the same WITH-clause may not use the same alias.
 */
public class WithClause extends StmtNode {
  /////////////////////////////////////////
  // BEGIN: Members that need to be reset()

  private final List<View> views_;

  // END: Members that need to be reset()
  /////////////////////////////////////////

  public WithClause(List<View> views) {
    Preconditions.checkNotNull(views);
    Preconditions.checkState(!views.isEmpty());
    views_ = views;
  }

  /**
   * Analyzes all views and registers them with the analyzer. Enforces scoping rules.
   * All local views registered with the analyzer are have QueryStmts with resolved
   * TableRefs to simplify the analysis of view references.
   */
  @Override
  public void analyze(Analyzer analyzer) throws AnalysisException {
    // Create a new analyzer for the WITH clause with a new global state (IMPALA-1357)
    // but a child of 'analyzer' so that the global state for 'analyzer' is not polluted
    // during analysis of the WITH clause. withClauseAnalyzer is a child of 'analyzer' so
    // that local views registered in parent blocks are visible here.
    Analyzer withClauseAnalyzer = Analyzer.createWithNewGlobalState(analyzer);
    withClauseAnalyzer.setHasWithClause();
    if (analyzer.isExplain()) withClauseAnalyzer.setIsExplain();
    for (View view: views_) {
      Analyzer viewAnalyzer = new Analyzer(withClauseAnalyzer);
      view.getQueryStmt().analyze(viewAnalyzer);
      // Register this view so that the next view can reference it.
      withClauseAnalyzer.registerLocalView(view);
    }
    // Register all local views with the analyzer.
    for (FeView localView: withClauseAnalyzer.getLocalViews().values()) {
      analyzer.registerLocalView(localView);
    }
    // Record audit events because the resolved table references won't generate any
    // when a view is referenced.
    analyzer.getAccessEvents().addAll(withClauseAnalyzer.getAccessEvents());

    // Register all privilege requests made from the root analyzer.
    for (PrivilegeRequest req: withClauseAnalyzer.getPrivilegeReqs()) {
      analyzer.registerPrivReq(req);
    }
  }

  /**
   * C'tor for cloning.
   */
  private WithClause(WithClause other) {
    Preconditions.checkNotNull(other);
    views_ = new ArrayList<>();
    for (View view: other.views_) {
      views_.add(new View(view.getName(), view.getQueryStmt().clone(),
          view.getOriginalColLabels()));
    }
  }

  public void reset() {
    for (View view: views_) view.getQueryStmt().reset();
  }

  @Override
  public WithClause clone() { return new WithClause(this); }

  @Override
  public final String toSql() {
    return toSql(DEFAULT);
  }

  @Override
  public String toSql(ToSqlOptions options) {
    List<String> viewStrings = new ArrayList<>();
    for (View view: views_) {
      // Enclose the view alias and explicit labels in quotes if Hive cannot parse it
      // without quotes. This is needed for view compatibility between Impala and Hive.
      String aliasSql = ToSqlUtils.getIdentSql(view.getName());
      if (view.getColLabels() != null) {
        aliasSql += "(" + Joiner.on(", ").join(
            ToSqlUtils.getIdentSqlList(view.getOriginalColLabels())) + ")";
      }
      viewStrings.add(aliasSql + " AS (" + view.getQueryStmt().toSql(options) + ")");
    }
    return "WITH " + Joiner.on(",").join(viewStrings);
  }

  public List<View> getViews() { return views_; }
}