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https://issues.apache.org/jira/browse/DRILL-6114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16366643#comment-16366643
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ASF GitHub Bot commented on DRILL-6114:
---------------------------------------
Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/1112#discussion_r168681901
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/record/metadata/AbstractColumnMetadata.java
---
@@ -0,0 +1,206 @@
+/*
+ * 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.drill.exec.record.metadata;
+
+import org.apache.drill.common.types.TypeProtos.DataMode;
+import org.apache.drill.common.types.TypeProtos.MajorType;
+import org.apache.drill.common.types.TypeProtos.MinorType;
+import org.apache.drill.exec.record.MaterializedField;
+
+/**
+ * Abstract definition of column metadata. Allows applications to create
+ * specialized forms of a column metadata object by extending from this
+ * abstract class.
+ * <p>
+ * Note that, by design, primitive columns do not have a link to their
+ * tuple parent, or their index within that parent. This allows the same
+ * metadata to be shared between two views of a tuple, perhaps physical
+ * and projected views. This restriction does not apply to map columns,
+ * since maps (and the row itself) will, by definition, differ between
+ * the two views.
+ */
+
+public abstract class AbstractColumnMetadata implements ColumnMetadata {
+
+ // Capture the key schema information. We cannot use the
MaterializedField
+ // or MajorType because then encode child information that we encode here
+ // as a child schema. Keeping the two in sync is nearly impossible.
+
+ protected final String name;
+ protected final MinorType type;
+ protected final DataMode mode;
+ protected final int precision;
+ protected final int scale;
+ protected boolean projected = true;
+
+ /**
+ * Predicted number of elements per array entry. Default is
+ * taken from the often hard-coded value of 10.
+ */
+
+ protected int expectedElementCount = 1;
+
+ public AbstractColumnMetadata(MaterializedField schema) {
+ name = schema.getName();
+ MajorType majorType = schema.getType();
+ type = majorType.getMinorType();
+ mode = majorType.getMode();
+ precision = majorType.getPrecision();
+ scale = majorType.getScale();
+ if (isArray()) {
+ expectedElementCount = DEFAULT_ARRAY_SIZE;
+ }
+ }
+
+ public AbstractColumnMetadata(String name, MinorType type, DataMode
mode) {
+ this.name = name;
+ this.type = type;
+ this.mode = mode;
+ precision = 0;
+ scale = 0;
+ if (isArray()) {
+ expectedElementCount = DEFAULT_ARRAY_SIZE;
+ }
+ }
+
+ public AbstractColumnMetadata(AbstractColumnMetadata from) {
+ name = from.name;
+ type = from.type;
+ mode = from.mode;
+ precision = from.precision;
+ scale = from.scale;
+ expectedElementCount = from.expectedElementCount;
+ }
+
+ protected void bind(TupleSchema parentTuple) { }
+
+ @Override
+ public String name() { return name; }
+
+ @Override
+ public MinorType type() { return type; }
+
+ @Override
+ public MajorType majorType() {
+ return MajorType.newBuilder()
+ .setMinorType(type())
+ .setMode(mode())
+ .build();
+ }
+
+ @Override
+ public DataMode mode() { return mode; }
+
+ @Override
+ public boolean isNullable() { return mode() == DataMode.OPTIONAL; }
+
+ @Override
+ public boolean isArray() { return mode() == DataMode.REPEATED; }
+
+ @Override
+ public int dimensions() { return isArray() ? 1 : 0; }
+
+ @Override
+ public boolean isMap() { return false; }
+
+ @Override
+ public boolean isVariant() { return false; }
--- End diff --
I think there is a write-up somewhere about this. "Variant" is an old term
from Visual Basic for a tagged union (which is what our "Union" type really
is.) It is used here because both a (non-repeated) List and a Union are both
unions, which is confusing, so I used a separate term. Also, the "Union" term
is confusing since there is also a UNION operator in SQL. `See
VariantMetadata.java`.
> Complete internal metadata layer for improved batch handling
> ------------------------------------------------------------
>
> Key: DRILL-6114
> URL: https://issues.apache.org/jira/browse/DRILL-6114
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Major
> Fix For: 1.13.0
>
>
> Slice of the ["batch handling"
> project.|https://github.com/paul-rogers/drill/wiki/Batch-Handling-Upgrades]
> that includes enhancements to the internal metadata system.
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