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From melrief <...@git.apache.org>
Subject [GitHub] accumulo pull request #145: ACCUMULO-4376 add KeyBuilder
Date Thu, 01 Sep 2016 20:34:18 GMT
Github user melrief commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/145#discussion_r77247911
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/data/KeyBuilder.java ---
    @@ -0,0 +1,278 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one or more
    + * contributor license agreements.  See the NOTICE file distributed with
    + * this work for additional information regarding copyright ownership.
    + * The ASF licenses this file to You under the Apache License, Version 2.0
    + * (the "License"); you may not use this file except in compliance with
    + * the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.accumulo.core.data;
    +
    +
    +import org.apache.hadoop.io.Text;
    +
    +/**
    + * A builder used to build <code>Key</code>s by defining their components.
    + *
    + * The rules are:
    + * <ul>
    + *   <li>All components of the <code>Key</code> are optional except
the row</li>
    + *   <li>Components not explicitly set default to empty byte array except the timestamp
which
    + *   defaults to <code>Long.MAX_VALUE</code></li>
    + *   <li>The column qualifier can only be set if the column family has been set
first</li>
    + *   <li>The column visibility can only be set if at least the column family has
been set first</li>
    + * </ul>
    + *
    + * The builder supports three types of components: <code>byte[]</code>, <code>Text</code>
and <code>CharSequence</code>.
    + *
    + * The builder is mutable and not thread safe.
    + *
    + * @see org.apache.accumulo.core.data.Key
    + * @since 1.8
    + */
    +public class KeyBuilder {
    +
    +  public interface Build<T> {
    +
    +    /**
    +     * Build a <code>Key</code> from this builder.
    +     *
    +     * @param copyBytes
    +     *          if the byte arrays should be copied or not. If not, byte arrays will
be reused in the resultant <code>Key</code>
    +     * @return
    +     *          the <code>Key</code> built from this builder
    +     */
    +    Key build(boolean copyBytes);
    +
    +    /**
    +     * Build a <code>Key</code> from this builder. copyBytes defaults to
true.
    +     *
    +     * @return
    +     *          the <code>Key</code> built from this builder
    +     */
    +    Key build();
    +
    +    /**
    +     * Change the timestamp of the <code>Key</code> created.
    +     *
    +     * @param timestamp
    +     *          the timestamp to use for the <code>Key</code>
    +     * @return this builder
    +     */
    +    Build<T> timestamp(long timestamp);
    +
    +    /**
    +     * Set the deleted marker of the <code>Key</code> to the parameter.
    +     *
    +     * @param deleted
    +     *          if the <code>Key</code> should be marked as deleted or not
    +     * @return this builder
    +     */
    +    Build<T> deleted(boolean deleted);
    +  }
    +
    +  public interface ColumnFamilyStep<T> extends ColumnVisibilityStep<T> {
    +
    +    /**
    +     * Set the column family of the <code>Key</code> that this builder will
build to the parameter.
    +     *
    +     * @param columnFamily
    +     *          the column family to use for the <code>Key</code>
    +     * @return this builder
    +     */
    +    ColumnQualifierStep<T> columnFamily(final T columnFamily);
    +
    +    /**
    +     * Set the column family, qualifier and visibility of the <code>Key</code>
that this builder will build to the parameter.
    +     *
    +     * @param columnFamily
    +     *          the column family to use for the <code>Key</code>
    +     * @param columnQualifier
    +     *          the column qualifier to use for the <code>Key</code>
    +     * @param columnVisibility
    +     *          the column visibility to use for the <code>Key</code>
    +     * @return this builder
    +     */
    +    Build<T> column(final T columnFamily, final T columnQualifier, final T columnVisibility);
    +
    +    /**
    +     * Set the column family and the qualifier of the <code>Key</code> that
this builder will build to the parameter.
    +     *
    +     * @param columnFamily
    +     *          the column family to use for the <code>Key</code>
    +     * @param columnQualifier
    +     *          the column qualifier to use for the <code>Key</code>
    +     * @return this builder
    +     */
    +    ColumnVisibilityStep<T> column(final T columnFamily, final T columnQualifier);
    +  }
    +
    +  public interface ColumnQualifierStep<T> extends ColumnVisibilityStep<T>
{
    +
    +    /**
    +     * Set the column qualifier of the <code>Key</code> that this builder
will build to the parameter.
    +     *
    +     * @param columnQualifier
    +     *          the column qualifier to use for the <code>Key</code>
    +     * @return this builder
    +     */
    +    ColumnVisibilityStep<T> columnQualifier(final T columnQualifier);
    +  }
    +
    +  public interface ColumnVisibilityStep<T> extends Build<T> {
    +    /**
    +     * Set the column qualifier of the <code>Key</code> that this builder
will build to the parameter.
    +     *
    +     * @param columnVisibility
    +     *          the column visibility to use for the <code>Key</code>
    +     * @return this builder
    +     */
    +    Build<T> columnVisibility(final T columnVisibility);
    +  }
    +
    +  private static abstract class AbstractKeyBuilder<T> implements ColumnFamilyStep<T>,
ColumnQualifierStep<T>,
    +      ColumnVisibilityStep<T> {
    +
    +    protected static final byte EMPTY_BYTES[] = new byte[0];
    +
    +    protected T row = null;
    +    protected T columnFamily = null;
    +    protected T columnQualifier = null;
    +    protected T columnVisibility = null;
    +    protected long timestamp = Long.MAX_VALUE;
    +    protected boolean deleted = false;
    +
    +    final public ColumnFamilyStep<T> row(final T row) {
    +      this.row = row;
    +      return this;
    +    }
    +
    +    @Override
    +    final public ColumnQualifierStep<T> columnFamily(final T columnFamily) {
    +      this.columnFamily = columnFamily;
    +      return this;
    +    }
    +
    +    @Override
    +    final public ColumnVisibilityStep<T> columnQualifier(final T columnQualifier)
{
    +      this.columnQualifier = columnQualifier;
    +      return this;
    +    }
    +
    +    @Override
    +    final public Build<T> columnVisibility(final T columnVisibility) {
    +      this.columnVisibility = columnVisibility;
    +      return this;
    +    }
    +
    +    @Override
    +    final public Build<T> timestamp(long timestamp) {
    +      this.timestamp = timestamp;
    +      return this;
    +    }
    +
    +    @Override
    +    public Build<T> deleted(boolean deleted) {
    +      this.deleted = deleted;
    +      return this;
    +    }
    +
    +    @Override
    +    public Key build() {
    +      return this.build(true);
    +    }
    +
    +    @Override
    +    public Build<T> column(final T columnFamily, final T columnQualifier, final
T columnVisibility) {
    +      return this.columnFamily(columnFamily).columnQualifier(columnQualifier).columnVisibility(columnVisibility);
    +    }
    +
    +    @Override
    +    public ColumnVisibilityStep<T> column(final T columnFamily, final T columnQualifier)
{
    +      return this.columnFamily(columnFamily).columnQualifier(columnQualifier);
    +    }
    +  }
    +
    +  private static class TextKeyBuilder extends AbstractKeyBuilder<Text> {
    +
    +    private final Text EMPTY_TEXT = new Text();
    +
    +    @Override
    +    public Key build(boolean copyBytes) {
    +      Text columnFamily = (this.columnFamily == null) ? EMPTY_TEXT : this.columnFamily;
    +      Text columnQualifier = (this.columnQualifier == null) ? EMPTY_TEXT : this.columnQualifier;
    +      Text columnVisibility = (this.columnVisibility == null) ? EMPTY_TEXT : this.columnVisibility;
    +      return new Key(row.getBytes(), 0, row.getLength(), columnFamily.getBytes(), 0,
columnFamily.getLength(),
    +          columnQualifier.getBytes(), 0, columnQualifier.getLength(), columnVisibility.getBytes(),
0,
    +          columnVisibility.getLength(), timestamp, deleted, copyBytes);
    +    }
    +  }
    +
    +  private static class ByteArrayKeyBuilder extends AbstractKeyBuilder<byte[]> {
    +
    +    @Override
    +    public Key build(boolean copyBytes) {
    +      byte[] columnFamily = (this.columnFamily == null) ? EMPTY_BYTES : this.columnFamily;
    +      byte[] columnQualifier = (this.columnQualifier == null) ? EMPTY_BYTES : this.columnQualifier;
    +      byte[] columnVisibility = (this.columnVisibility == null) ? EMPTY_BYTES : this.columnVisibility;
    +      return new Key(row, columnFamily, columnQualifier, columnVisibility, timestamp,
deleted, copyBytes);
    +    }
    +  }
    +
    +  private static class CharSequenceKeyBuilder extends AbstractKeyBuilder<CharSequence>
{
    +
    +    private final Text EMPTY_TEXT = new Text();
    +
    +    @Override
    +    public Key build(boolean copyBytes) {
    --- End diff --
    
    No it doesn't for now because I'm still not sure if I can access the underlying array
of a `CharSequence`. The issue is that not all types will allow to access their underlying
bytes and with a common interface there is no way to set this flag only for the types that
support this.
    One solution would be to have another interface for types that support the use of the
underlying bytes so that those types have the possibility to set the `copyBytes` flag and
the others not but this complicates the things a little bit and it wouldn't play well with
heterogeneous components. For instance, if I have
    
    ```java
    byte r[];
    String f;
    Text q;
    
    Key k = Key.newBuilder().row(r).family(f).qualifier(q).build();
    ```
    
    Does build takes the flag `copyBytes` or not considering that `f` won't use the underlying
array anyway? Shall we add the flag to each component method so that we can decide only for
components that make sense? I think I rather prefer to have the flag regardless of the type
with the idea what if the flag is set to `false` but the type doesn't support direct access
to the underlying array, then the flag is ignored and bytes are copied.


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