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| <div class="subTitle">org.apache.drill.exec.vector.accessor</div> |
| <h2 title="Interface ColumnReaderIndex" class="title">Interface ColumnReaderIndex</h2> |
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| <dl> |
| <dt>All Known Implementing Classes:</dt> |
| <dd><a href="../../../../../../org/apache/drill/exec/vector/accessor/reader/ArrayReaderImpl.ElementReaderIndex.html" title="class in org.apache.drill.exec.vector.accessor.reader">ArrayReaderImpl.ElementReaderIndex</a>, <a href="../../../../../../org/apache/drill/exec/physical/resultSet/model/single/DirectRowIndex.html" title="class in org.apache.drill.exec.physical.resultSet.model.single">DirectRowIndex</a>, <a href="../../../../../../org/apache/drill/exec/physical/rowSet/HyperRowIndex.html" title="class in org.apache.drill.exec.physical.rowSet">HyperRowIndex</a>, <a href="../../../../../../org/apache/drill/exec/physical/rowSet/IndirectRowIndex.html" title="class in org.apache.drill.exec.physical.rowSet">IndirectRowIndex</a>, <a href="../../../../../../org/apache/drill/exec/physical/resultSet/model/ReaderIndex.html" title="class in org.apache.drill.exec.physical.resultSet.model">ReaderIndex</a></dd> |
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| <br> |
| <pre>public interface <span class="typeNameLabel">ColumnReaderIndex</span></pre> |
| <div class="block">The reader structure is heavily recursive. The top-level reader |
| iterates over batches, possibly through an indirection vector |
| (SV2 or SV4.) The row is tuple of top-level vectors. Each top-level |
| vector may be an array. Iteration through the array works identically |
| to iteration over the batch as a whole. (In fact, the scalar readers |
| don't know if they are top-level or array readers.) Array nesting |
| can continue to any level of depth. |
| <p> |
| Further, when used with a logical join, the top-level iteration |
| may be over an array, with an implicit join out to enclosing nesting |
| levels. |
| <p> |
| Because of this, the same index interface must work at all nesting |
| levels: at the top, and within arrays. This interface |
| supports a usage model as follows:<pre><code> |
| ColumnReaderIndex index = ... |
| while (index.hasNext()) { |
| index.next(); |
| int hyperIndex = index.hyperVectorIndex(); |
| int vectorOffset = index.offset(); |
| }</code></pre> |
| <p> |
| When convenient, the following abbreviated form is also |
| supported:<pre><code> |
| ColumnReaderIndex index = ... |
| while (index.next()) { |
| int hyperIndex = index.hyperVectorIndex(); |
| int vectorOffset = index.offset(); |
| }</code></pre> |
| <p> |
| For a top-level index, the check of <tt>hasNext()</tt> and |
| call to <tt>next()</tt> is done by the row set reader. For |
| arrays, the call to <tt>hasNext()</tt> is done by the array |
| reader. The call to <tt>next()</tt> is done by the scalar |
| reader (for scalar arrays) or the array reader (for other |
| arrays.) |
| <p> |
| The hyper-vector index has meaning only for top-level vectors, |
| and is ignored by nested vectors. (Nested vectors work by navigating |
| down from a top-level vector.) But, as noted above, any given |
| reader does not know if it is at the top or nested level, instead |
| it is the <a href="../../../../../../org/apache/drill/exec/vector/accessor/reader/VectorAccessor.html" title="interface in org.apache.drill.exec.vector.accessor.reader"><code>VectorAccessor</code></a> |
| abstraction that works out the nesting levels.</div> |
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| <td class="colFirst"><code>boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/drill/exec/vector/accessor/ColumnReaderIndex.html#hasNext--">hasNext</a></span>()</code> |
| <div class="block">Reports if the index has another item.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>int</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/drill/exec/vector/accessor/ColumnReaderIndex.html#hyperVectorIndex--">hyperVectorIndex</a></span>()</code> |
| <div class="block">When used with a hyper-vector (SV4) based batch, returns the |
| index of the current batch within the hyper-batch.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>int</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/drill/exec/vector/accessor/ColumnReaderIndex.html#logicalIndex--">logicalIndex</a></span>()</code> |
| <div class="block">Ordinal index within the batch or array.</div> |
| </td> |
| </tr> |
| <tr id="i3" class="rowColor"> |
| <td class="colFirst"><code>boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/drill/exec/vector/accessor/ColumnReaderIndex.html#next--">next</a></span>()</code> |
| <div class="block">Advances the index to the next position.</div> |
| </td> |
| </tr> |
| <tr id="i4" class="altColor"> |
| <td class="colFirst"><code>int</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/drill/exec/vector/accessor/ColumnReaderIndex.html#offset--">offset</a></span>()</code> |
| <div class="block">Vector offset to read.</div> |
| </td> |
| </tr> |
| <tr id="i5" class="rowColor"> |
| <td class="colFirst"><code>int</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/drill/exec/vector/accessor/ColumnReaderIndex.html#size--">size</a></span>()</code> |
| <div class="block">Return the number of items that this index indexes: top-level record |
| count for the root index; total element count for nested arrays.</div> |
| </td> |
| </tr> |
| </table> |
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| <h4>logicalIndex</h4> |
| <pre>int logicalIndex()</pre> |
| <div class="block">Ordinal index within the batch or array. Increments from -1. |
| (The position before the first item.) |
| Identifies the logical row number of top-level records, |
| or the array element for arrays. Actual physical |
| index may be different if an indirection layer is in use.</div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>logical read index</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="hyperVectorIndex--"> |
| <!-- --> |
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| <h4>hyperVectorIndex</h4> |
| <pre>int hyperVectorIndex()</pre> |
| <div class="block">When used with a hyper-vector (SV4) based batch, returns the |
| index of the current batch within the hyper-batch. If this is |
| a single batch, or a nested index, then always returns 0.</div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>batch index of the current row within the |
| hyper-batch</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="offset--"> |
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| <h4>offset</h4> |
| <pre>int offset()</pre> |
| <div class="block">Vector offset to read. For top-level vectors, the offset may be |
| through an indirection (SV2 or SV4). For arrays, the offset is the |
| absolute position, with the vector of the current array element.</div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>vector read index</dd> |
| </dl> |
| </li> |
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| <!-- --> |
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| <h4>next</h4> |
| <pre>boolean next()</pre> |
| <div class="block">Advances the index to the next position. Used: |
| <ul> |
| <li>At the top level for normal readers or</li> |
| <liAt a nested level for implicit join readers, and</li> |
| <li>An each array level to iterate over arrays.</li> |
| </ul></div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>true if another value is available, false if EOF</dd> |
| </dl> |
| </li> |
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| <h4>hasNext</h4> |
| <pre>boolean hasNext()</pre> |
| <div class="block">Reports if the index has another item.</div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd><true> if more rows remain. That is, if a |
| call to <a href="../../../../../../org/apache/drill/exec/vector/accessor/ColumnReaderIndex.html#next--"><code>next()</code></a> would return <tt>true</tt>.</dd> |
| </dl> |
| </li> |
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| <h4>size</h4> |
| <pre>int size()</pre> |
| <div class="block">Return the number of items that this index indexes: top-level record |
| count for the root index; total element count for nested arrays.</div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>element count at this index level</dd> |
| </dl> |
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