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| <h2 title="Interface ManagedReader" class="title">Interface ManagedReader<T extends <a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/SchemaNegotiator.html" title="interface in org.apache.drill.exec.physical.impl.scan.framework">SchemaNegotiator</a>></h2> |
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| <dd><a href="../../../../../../../../org/apache/drill/exec/store/avro/AvroBatchReader.html" title="class in org.apache.drill.exec.store.avro">AvroBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/easy/text/reader/CompliantTextBatchReader.html" title="class in org.apache.drill.exec.store.easy.text.reader">CompliantTextBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/enumerable/EnumerableRecordReader.html" title="class in org.apache.drill.exec.store.enumerable">EnumerableRecordReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/excel/ExcelBatchReader.html" title="class in org.apache.drill.exec.store.excel">ExcelBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/mock/ExtendedMockBatchReader.html" title="class in org.apache.drill.exec.store.mock">ExtendedMockBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/hdf5/HDF5BatchReader.html" title="class in org.apache.drill.exec.store.hdf5">HDF5BatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/http/HttpBatchReader.html" title="class in org.apache.drill.exec.store.http">HttpBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/http/HttpCSVBatchReader.html" title="class in org.apache.drill.exec.store.http">HttpCSVBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/httpd/HttpdLogBatchReader.html" title="class in org.apache.drill.exec.store.httpd">HttpdLogBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/http/HttpXMLBatchReader.html" title="class in org.apache.drill.exec.store.http">HttpXMLBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/iceberg/read/IcebergRecordReader.html" title="class in org.apache.drill.exec.store.iceberg.read">IcebergRecordReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/image/ImageBatchReader.html" title="class in org.apache.drill.exec.store.image">ImageBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/jdbc/JdbcBatchReader.html" title="class in org.apache.drill.exec.store.jdbc">JdbcBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/kafka/KafkaRecordReader.html" title="class in org.apache.drill.exec.store.kafka">KafkaRecordReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/log/LogBatchReader.html" title="class in org.apache.drill.exec.store.log">LogBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/pcap/PcapBatchReader.html" title="class in org.apache.drill.exec.store.pcap">PcapBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/pcapng/PcapngBatchReader.html" title="class in org.apache.drill.exec.store.pcapng">PcapngBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/pdf/PdfBatchReader.html" title="class in org.apache.drill.exec.store.pdf">PdfBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/phoenix/PhoenixBatchReader.html" title="class in org.apache.drill.exec.store.phoenix">PhoenixBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/sas/SasBatchReader.html" title="class in org.apache.drill.exec.store.sas">SasBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/easy/sequencefile/SequenceFileBatchReader.html" title="class in org.apache.drill.exec.store.easy.sequencefile">SequenceFileBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/esri/ShpBatchReader.html" title="class in org.apache.drill.exec.store.esri">ShpBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/splunk/SplunkBatchReader.html" title="class in org.apache.drill.exec.store.splunk">SplunkBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/spss/SpssBatchReader.html" title="class in org.apache.drill.exec.store.spss">SpssBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/syslog/SyslogBatchReader.html" title="class in org.apache.drill.exec.store.syslog">SyslogBatchReader</a>, <a href="../../../../../../../../org/apache/drill/exec/store/xml/XMLBatchReader.html" title="class in org.apache.drill.exec.store.xml">XMLBatchReader</a></dd> |
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| <pre>public interface <span class="typeNameLabel">ManagedReader<T extends <a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/SchemaNegotiator.html" title="interface in org.apache.drill.exec.physical.impl.scan.framework">SchemaNegotiator</a>></span></pre> |
| <div class="block">Extended version of a record reader which uses a size-aware batch mutator. |
| Use this for all new readers. Replaces the original |
| <a href="../../../../../../../../org/apache/drill/exec/store/RecordReader.html" title="interface in org.apache.drill.exec.store"><code>RecordReader</code></a> interface. |
| <p> |
| This interface is used to create readers that work with the projection |
| mechanism to provide services for handling projection, setting up the result |
| set loader, handling schema smoothing, sharing vectors across batches, etc. |
| <p> |
| Note that this interface reads a <b>batch</b> of rows, not a single row. (The |
| original <tt>RecordReader</tt> could be confusing in this aspect.) |
| <p> |
| The expected lifecycle is: |
| <ul> |
| <li>Constructor: allocate no resources. Obtain a reference to a reader-specific |
| schema and projection manager.</li> |
| <li><a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html#open-T-"><code>open(SchemaNegotiator)</code></a>: Use the provided <a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/SchemaNegotiator.html" title="interface in org.apache.drill.exec.physical.impl.scan.framework"><code>SchemaNegotiator</code></a> to configure the |
| scanner framework for this reader by specifying a schema (if known), desired |
| row counts and other configuration options. Call <a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/SchemaNegotiator.html#build--"><code>SchemaNegotiator.build()</code></a> |
| to obtain a <a href="../../../../../../../../org/apache/drill/exec/physical/resultSet/RowSetLoader.html" title="interface in org.apache.drill.exec.physical.resultSet"><code>RowSetLoader</code></a> |
| to use to capture the rows that the reader reads.</li> |
| <li><a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html#next--"><code>next()</code></a>: called for each batch. The batch is written using the |
| result set loader obtained above. The scanner framework handles details of |
| tracking version changes, handling overflow, limiting record counts, and |
| so on. Return <tt>true</tt> to indicate a batch is available, <tt>false</tt> |
| to indicate EOF. The first call to <tt>next()</tt> can return <tt>false</tt> |
| if the data source has no rows.</li> |
| <li><a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html#close--"><code>close()</code></a>: called to release resources. May be called before |
| <tt>next()</tt> returns </tt>false</tt>.</li> |
| <p> |
| If an error occurs, the reader can throw a <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/RuntimeException.html?is-external=true" title="class or interface in java.lang"><code>RuntimeException</code></a> |
| from any method. A <tt>UserException</tt> is preferred to provide |
| detailed information about the source of the problem.</div> |
| </li> |
| </ul> |
| </div> |
| <div class="summary"> |
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| <!-- ========== METHOD SUMMARY =========== --> |
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| <h3>Method Summary</h3> |
| <table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Method Summary table, listing methods, and an explanation"> |
| <caption><span id="t0" class="activeTableTab"><span>All Methods</span><span class="tabEnd"> </span></span><span id="t2" class="tableTab"><span><a href="javascript:show(2);">Instance Methods</a></span><span class="tabEnd"> </span></span><span id="t3" class="tableTab"><span><a href="javascript:show(4);">Abstract Methods</a></span><span class="tabEnd"> </span></span></caption> |
| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colLast" scope="col">Method and Description</th> |
| </tr> |
| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code>void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html#close--">close</a></span>()</code> |
| <div class="block">Release resources.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html#next--">next</a></span>()</code> |
| <div class="block">Read the next batch.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html#open-T-">open</a></span>(<a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html" title="type parameter in ManagedReader">T</a> negotiator)</code> |
| <div class="block">Setup the record reader.</div> |
| </td> |
| </tr> |
| </table> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </div> |
| <div class="details"> |
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| <!-- ============ METHOD DETAIL ========== --> |
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| <!-- --> |
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| <h3>Method Detail</h3> |
| <a name="open-org.apache.drill.exec.physical.impl.scan.framework.SchemaNegotiator-"> |
| <!-- --> |
| </a><a name="open-T-"> |
| <!-- --> |
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| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>open</h4> |
| <pre>boolean open(<a href="../../../../../../../../org/apache/drill/exec/physical/impl/scan/framework/ManagedReader.html" title="type parameter in ManagedReader">T</a> negotiator)</pre> |
| <div class="block">Setup the record reader. Called just before the first call |
| to <tt>next()</tt>. Allocate resources here, not in the constructor. |
| Example: open files, allocate buffers, etc.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>negotiator</code> - mechanism to negotiate select and table |
| schemas, then create the row set reader used to load data into |
| value vectors</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>true if the reader is open and ready to read (possibly no) |
| rows. false for a "soft" failure in which no schema or data is available, |
| but the scanner should not fail, it should move onto another reader</dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/RuntimeException.html?is-external=true" title="class or interface in java.lang">RuntimeException</a></code> - for "hard" errors that should terminate |
| the query. <tt>UserException</tt> preferred to explain the problem |
| better than the scan operator can by guessing at the cause</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="next--"> |
| <!-- --> |
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| <h4>next</h4> |
| <pre>boolean next()</pre> |
| <div class="block">Read the next batch. Reading continues until either EOF, |
| or until the mutator indicates that the batch is full. |
| The batch is considered valid if it is non-empty. Returning |
| <tt>true</tt> with an empty batch is valid, and is helpful on |
| the very first batch (returning schema only.) An empty batch |
| with a <tt>false</tt> return code indicates EOF and the batch |
| will be discarded. A non-empty batch along with a <tt>false</tt> |
| return result indicates a final, valid batch, but that EOF was |
| reached and no more data is available. |
| <p> |
| This somewhat complex protocol avoids the need to allocate a |
| final batch just to find out that no more data is available; |
| it allows EOF to be returned along with the final batch.</div> |
| <dl> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd><tt>true</tt> if more data may be available (and so |
| <tt>next()</tt> should be called again, <tt>false</tt> to indicate |
| that EOF was reached</dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/RuntimeException.html?is-external=true" title="class or interface in java.lang">RuntimeException</a></code> - (<tt>UserException</tt> preferred) if an |
| error occurs that should fail the query.</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="close--"> |
| <!-- --> |
| </a> |
| <ul class="blockListLast"> |
| <li class="blockList"> |
| <h4>close</h4> |
| <pre>void close()</pre> |
| <div class="block">Release resources. Called just after a failure, when the scanner |
| is cancelled, or after <tt>next()</tt> returns EOF. Release |
| all resources and close files. Guaranteed to be called if |
| <tt>open()</tt> returns normally; will not be called if <tt>open()</tt> |
| throws an exception.</div> |
| <dl> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="https://docs.oracle.com/javase/8/docs/api/java/lang/RuntimeException.html?is-external=true" title="class or interface in java.lang">RuntimeException</a></code> - (<tt>UserException</tt> preferred) if an |
| error occurs that should fail the query.</dd> |
| </dl> |
| </li> |
| </ul> |
| </li> |
| </ul> |
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