ebean/src/main/java/io/ebeaninternal/server/deploy/TableJoin.java

package io.ebeaninternal.server.deploy;

import io.ebean.util.SplitName;
import io.ebeaninternal.server.core.InternString;
import io.ebeaninternal.server.deploy.meta.DeployTableJoin;
import io.ebeaninternal.server.deploy.meta.DeployTableJoinColumn;
import io.ebeaninternal.server.query.SqlJoinType;

/**
 * Represents a join to another table.
 */
public final class TableJoin {

  /**
   * The joined table.
   */
  private final String table;

  /**
   * The type of join as per deployment (cardinality and optionality).
   */
  private final SqlJoinType type;

  private final InheritInfo inheritInfo;

  /**
   * Columns as an array.
   */
  private final TableJoinColumn[] columns;

  /**
   * A hash that can be used with the query plan.
   */
  private final int queryHash;

  /**
   * Create a TableJoin.
   */
  public TableJoin(DeployTableJoin deploy) {

    this.table = InternString.intern(deploy.getTable());
    this.type = deploy.getType();
    this.inheritInfo = deploy.getInheritInfo();

    DeployTableJoinColumn[] deployCols = deploy.columns();
    this.columns = new TableJoinColumn[deployCols.length];
    for (int i = 0; i < deployCols.length; i++) {
      this.columns[i] = new TableJoinColumn(deployCols[i]);
    }

    this.queryHash = calcQueryHash();
  }

  private TableJoin(TableJoin source, String overrideColumn) {
    this.table = source.table;
    this.type = source.type;
    this.inheritInfo = source.inheritInfo;
    this.columns = new TableJoinColumn[1];
    this.columns[0] = source.columns[0].withOverrideColumn(overrideColumn);
    this.queryHash = calcQueryHash();
  }

  /**
   * Calculate a hash value for adding to a query plan.
   */
  private int calcQueryHash() {
    int hc = type.hashCode();
    hc = hc * 92821 + (table == null ? 0 : table.hashCode());
    for (TableJoinColumn column : columns) {
      hc = hc * 92821 + column.queryHash();
    }
    return hc;
  }

  @Override
  public int hashCode() {
    return queryHash;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;

    TableJoin that = (TableJoin) o;

    if (!table.equals(that.table)) return false;
    if (type != that.type) return false;
    if (columns.length != that.columns.length) return false;

    for (int i = 0; i < columns.length; i++) {
      if (!columns[i].equals(that.columns[i])) {
        return false;
      }
    }
    return true;
  }


  /**
   * Return a hash value for adding to a query plan.
   */
  public int queryHash() {
    return queryHash;
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder(30);
    sb.append(type).append(" ").append(table).append(" ");
    for (TableJoinColumn column : columns) {
      sb.append(column).append(" ");
    }
    return sb.toString();
  }

  /**
   * Return the join columns.
   */
  public TableJoinColumn[] columns() {
    return columns;
  }

  /**
   * Return the joined table name.
   */
  public String getTable() {
    return table;
  }

  /**
   * Return the type of join. LEFT JOIN etc.
   */
  public SqlJoinType getType() {
    return type;
  }

  public SqlJoinType addJoin(SqlJoinType joinType, String prefix, DbSqlContext ctx, String predicate) {
    String[] names = SplitName.split(prefix);
    String a1 = ctx.getTableAlias(names[0]);
    String a2 = ctx.getTableAlias(prefix);

    SqlJoinType returnJoinType = addJoin(joinType, a1, a2, ctx);
    ctx.append("and ").append(a2).append(predicate);
    return returnJoinType;
  }

  public SqlJoinType addJoin(SqlJoinType joinType, String prefix, DbSqlContext ctx) {

    String[] names = SplitName.split(prefix);
    String a1 = ctx.getTableAlias(names[0]);
    String a2 = ctx.getTableAlias(prefix);

    return addJoin(joinType, a1, a2, ctx);
  }

  public SqlJoinType addJoin(SqlJoinType joinType, String a1, String a2, DbSqlContext ctx) {

    String inheritance = inheritInfo != null ? inheritInfo.getWhere() : null;

    String joinLiteral = joinType.getLiteral(type);
    ctx.addJoin(joinLiteral, table, columns(), a1, a2, inheritance);

    return joinType.autoToOuter(type);
  }

  public void addJoin(String a1, String a2, StringBuilder sb) {
    for (int i = 0; i < columns.length; i++) {
      TableJoinColumn pair = columns[i];
      if (i > 0) {
        sb.append(" and ");
      }
      sb.append(a1).append(".").append(pair.getLocalDbColumn());
      sb.append(" = ");
      sb.append(a2).append(".").append(pair.getForeignDbColumn());
    }
  }

  TableJoin withOverrideColumn(String overrideColumn) {
    if (columns.length == 1 && overrideColumn != null && !overrideColumn.equals(columns[0].getLocalDbColumn())) {
      return new TableJoin(this, overrideColumn);
    }
    return this;
  }
}