com.github.explainable.sql.table.TempTable.java Source code

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Here is the source code for com.github.explainable.sql.table.TempTable.java

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/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2014 Gabriel Bender
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.github.explainable.sql.table;

import com.github.explainable.sql.ast.select.SqlSelectStmt;
import com.github.explainable.sql.type.SchemaTableType;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import javax.annotation.Nullable;

/**
 * Class that represents a temporary table that exists only during the execution of a single query.
 * For instance, the query {@code SELECT sid FROM (SELECT sid FROM Sailors) AS Temp} uses a
 * temporary table {@code Temp} with alias {@code Temp} and body {@code SELECT sid FROM Sailors}.
 */
public final class TempTable extends Table {
    private final SqlSelectStmt body;

    private final String alias;

    private final NestedScope scope;

    // Lazily initialized; should only be accessed using columns().
    @Nullable
    private ImmutableList<TempColumn> columns;

    TempTable(SqlSelectStmt body, String alias, NestedScope scope) {
        this.body = Preconditions.checkNotNull(body);
        this.alias = Preconditions.checkNotNull(alias);
        this.scope = Preconditions.checkNotNull(scope);
        this.columns = null;
    }

    SchemaTableType type() {
        return body.getType();
    }

    /**
     * Initialization of the table columns occurs the first time this method is called. The return
     * value is memoized, and the same result is returned on all subsequent calls.
     *
     * @return The columns in the table
     */
    @Override
    public ImmutableList<TempColumn> columns() {
        if (columns == null) {
            ImmutableList<String> columnNames = body.columnNames();
            ImmutableList.Builder<TempColumn> columnsBuilder = ImmutableList.builder();

            for (int i = 0; i < columnNames.size(); i++) {
                columnsBuilder.add(new TempColumn(columnNames.get(i), i, this));
            }

            columns = columnsBuilder.build();
        }

        return columns;
    }

    @Override
    public String alias() {
        return alias;
    }

    NestedScope scope() {
        return scope;
    }

    @Override
    public String toString() {
        return Objects.toStringHelper(this).add("body", body).toString();
    }
}