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| <dt>All Known Subinterfaces:</dt> |
| <dd><code><a href="BuiltInMetadata.All.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.All</a></code>, <code><a href="BuiltInMetadata.AllPredicates.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.AllPredicates</a></code>, <code><a href="BuiltInMetadata.Collation.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.Collation</a></code>, <code><a href="BuiltInMetadata.ColumnOrigin.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.ColumnOrigin</a></code>, <code><a href="BuiltInMetadata.ColumnUniqueness.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.ColumnUniqueness</a></code>, <code><a href="BuiltInMetadata.CumulativeCost.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.CumulativeCost</a></code>, <code><a href="BuiltInMetadata.DistinctRowCount.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.DistinctRowCount</a></code>, <code><a href="BuiltInMetadata.Distribution.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.Distribution</a></code>, <code><a href="BuiltInMetadata.ExplainVisibility.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.ExplainVisibility</a></code>, <code><a href="BuiltInMetadata.ExpressionLineage.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.ExpressionLineage</a></code>, <code><a href="BuiltInMetadata.MaxRowCount.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.MaxRowCount</a></code>, <code><a href="BuiltInMetadata.Memory.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.Memory</a></code>, <code><a href="BuiltInMetadata.MinRowCount.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.MinRowCount</a></code>, <code><a href="BuiltInMetadata.NodeTypes.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.NodeTypes</a></code>, <code><a href="BuiltInMetadata.NonCumulativeCost.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.NonCumulativeCost</a></code>, <code><a href="BuiltInMetadata.Parallelism.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.Parallelism</a></code>, <code><a href="BuiltInMetadata.PercentageOriginalRows.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.PercentageOriginalRows</a></code>, <code><a href="BuiltInMetadata.PopulationSize.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.PopulationSize</a></code>, <code><a href="BuiltInMetadata.Predicates.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.Predicates</a></code>, <code><a href="BuiltInMetadata.RowCount.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.RowCount</a></code>, <code><a href="BuiltInMetadata.Selectivity.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.Selectivity</a></code>, <code><a href="BuiltInMetadata.Size.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.Size</a></code>, <code><a href="BuiltInMetadata.TableReferences.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.TableReferences</a></code>, <code><a href="BuiltInMetadata.UniqueKeys.html" title="interface in org.apache.calcite.rel.metadata">BuiltInMetadata.UniqueKeys</a></code></dd> |
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| <pre>public interface <span class="typeNameLabel">Metadata</span></pre> |
| <div class="block">Metadata about a relational expression. |
| |
| <p>For particular types of metadata, a sub-class defines one of more methods |
| to query that metadata. Then a <a href="RelMetadataProvider.html" title="interface in org.apache.calcite.rel.metadata"><code>RelMetadataProvider</code></a> can offer those |
| kinds of metadata for particular sub-classes of <a href="../RelNode.html" title="interface in org.apache.calcite.rel"><code>RelNode</code></a>. |
| |
| <p>User code (typically in a planner rule or an implementation of |
| <a href="../RelNode.html#computeSelfCost(org.apache.calcite.plan.RelOptPlanner,org.apache.calcite.rel.metadata.RelMetadataQuery)"><code>RelNode.computeSelfCost(org.apache.calcite.plan.RelOptPlanner, RelMetadataQuery)</code></a>) |
| acquires a <code>Metadata</code> instance by calling <a href="../RelNode.html#metadata(java.lang.Class,org.apache.calcite.rel.metadata.RelMetadataQuery)"><code>RelNode.metadata(java.lang.Class<M>, org.apache.calcite.rel.metadata.RelMetadataQuery)</code></a>. |
| |
| <p>A <code>Metadata</code> instance already knows which particular <code>RelNode</code> |
| it is describing, so the methods do not pass in the <code>RelNode</code>. In fact, |
| quite a few metadata methods have no extra parameters. For instance, you can |
| get the row-count as follows:</p> |
| |
| <blockquote><pre><code> |
| RelNode rel; |
| double rowCount = rel.metadata(RowCount.class).rowCount(); |
| </code></pre></blockquote></div> |
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| <td class="colFirst"><code><a href="../RelNode.html" title="interface in org.apache.calcite.rel">RelNode</a></code></td> |
| <th class="colSecond" scope="row"><code><span class="memberNameLink"><a href="#rel()">rel</a></span>()</code></th> |
| <td class="colLast"> |
| <div class="block">Returns the relational expression that this metadata is about.</div> |
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| <h4>rel</h4> |
| <pre class="methodSignature"><a href="../RelNode.html" title="interface in org.apache.calcite.rel">RelNode</a> rel()</pre> |
| <div class="block">Returns the relational expression that this metadata is about.</div> |
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