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https://issues.apache.org/jira/browse/HAWQ-178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15124186#comment-15124186
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ASF GitHub Bot commented on HAWQ-178:
-------------------------------------
Github user hornn commented on a diff in the pull request:
https://github.com/apache/incubator-hawq/pull/302#discussion_r51313817
--- Diff:
pxf/pxf-json/src/main/java/org/apache/hawq/pxf/plugins/json/JsonResolver.java
---
@@ -0,0 +1,259 @@
+package org.apache.hawq.pxf.plugins.json;
+
+/*
+ * 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.
+ */
+
+import java.io.IOException;
+import java.security.InvalidParameterException;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.apache.hawq.pxf.api.OneField;
+import org.apache.hawq.pxf.api.OneRow;
+import org.apache.hawq.pxf.api.ReadResolver;
+import org.apache.hawq.pxf.api.io.DataType;
+import org.apache.hawq.pxf.api.utilities.ColumnDescriptor;
+import org.apache.hawq.pxf.api.utilities.InputData;
+import org.apache.hawq.pxf.api.utilities.Plugin;
+import org.codehaus.jackson.JsonNode;
+
+/**
+ * This JSON resolver for PXF will decode a given object from the {@link
JsonAccessor} into a row for HAWQ. It will
+ * decode this data into a JsonNode and walk the tree for each column. It
supports normal value mapping via projections
+ * and JSON array indexing.
+ */
+public class JsonResolver extends Plugin implements ReadResolver {
+
+ private ArrayList<OneField> list = new ArrayList<OneField>();
+
+ public JsonResolver(InputData inputData) throws Exception {
+ super(inputData);
+ }
+
+ @Override
+ public List<OneField> getFields(OneRow row) throws Exception {
+ list.clear();
+
+ // key is a Text object
+ JsonNode root =
JsonInputFormat.decodeLineToJsonNode(row.getKey().toString());
+
+ // if we weren't given a null object
+ if (root != null) {
+ // Iterate through the column definition and fetch our
JSON data
+ for (int i = 0; i < inputData.getColumns(); ++i) {
+
+ // Get the current column description
+ ColumnDescriptor cd = inputData.getColumn(i);
+ DataType columnType =
DataType.get(cd.columnTypeCode());
+
+ // Get the JSON projections from the column name
+ // For example, "user.name" turns into
["user","name"]
+ String[] projs = cd.columnName().split("\\.");
+
+ // Move down the JSON path to the final name
+ JsonNode node = getPriorJsonNode(root, projs);
+
+ // If this column is an array index, ex.
"tweet.hashtags[0]"
+ if (isArrayIndex(projs)) {
+
+ // Get the node name and index
+ String nodeName = getArrayName(projs);
+ int arrayIndex = getArrayIndex(projs);
+
+ // Move to the array node
+ node = node.get(nodeName);
+
+ // If this node is null or missing, add
a null value here
+ if (node == null ||
node.isMissingNode()) {
+ addNullField(columnType);
+ } else if (node.isArray()) {
+ // If the JSON node is an
array, then add it to our list
+
addFieldFromJsonArray(columnType, node, arrayIndex);
+ } else {
+ throw new
InvalidParameterException(nodeName + " is not an array node");
+ }
+ } else {
+ // This column is not an array type
+ // Move to the final node
+ node = node.get(projs[projs.length -
1]);
+
+ // If this node is null or missing, add
a null value here
+ if (node == null ||
node.isMissingNode()) {
+ addNullField(columnType);
+ } else {
+ // Else, add the value to the
record
+
addFieldFromJsonNode(columnType, node);
+ }
+ }
+ }
+ }
+
+ return list;
+ }
+
+ /**
+ * Iterates down the root node to the prior JSON node. This node is used
+ *
+ * @param root
+ * @param projs
+ * @return
+ */
+ private JsonNode getPriorJsonNode(JsonNode root, String[] projs) {
+
+ // Iterate through all the tokens to the desired JSON node
+ JsonNode node = root;
+ for (int j = 0; j < projs.length - 1; ++j) {
+ node = node.path(projs[j]);
+ }
+
+ return node;
+ }
+
+ /**
+ * Gets a boolean value indicating if this column is an array index
column
+ *
+ * @param projs
+ * The array of JSON projections
+ * @throws ArrayIndexOutOfBoundsException
+ */
+ private boolean isArrayIndex(String[] projs) {
+ return projs[projs.length - 1].contains("[") &&
projs[projs.length - 1].contains("]");
+ }
+
+ /**
+ * Gets the node name from the given String array of JSON projections,
parsed from the ColumnDescriptor's
+ *
+ * @param projs
+ * The array of JSON projections
+ * @return The name
+ * @throws ArrayIndexOutOfBoundsException
+ */
+ private String getArrayName(String[] projs) {
+ return projs[projs.length - 1].replaceAll("\\[[0-9]+\\]", "");
+ }
+
+ /**
+ * Gets the array index from the given String array of JSON
projections, parsed from the ColumnDescriptor's name
+ *
+ * @param projs
+ * The array of JSON projections
+ * @return The index
+ * @throws ArrayIndexOutOfBoundsException
+ */
+ private int getArrayIndex(String[] projs) {
+ return Integer.parseInt(projs[projs.length -
1].substring(projs[projs.length - 1].indexOf('[') + 1,
--- End diff --
perhaps use a variable for `String arrayElem = projs[projs.length - 1]` -
will make the code shorter.
> Add JSON plugin support in code base
> ------------------------------------
>
> Key: HAWQ-178
> URL: https://issues.apache.org/jira/browse/HAWQ-178
> Project: Apache HAWQ
> Issue Type: New Feature
> Components: PXF
> Reporter: Goden Yao
> Assignee: Goden Yao
> Fix For: backlog
>
> Attachments: PXFJSONPluginforHAWQ2.0andPXF3.0.0.pdf
>
>
> JSON has been a popular format used in HDFS as well as in the community,
> there has been a few JSON PXF plugins developed by the community and we'd
> like to see it being incorporated into the code base as an optional package.
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