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https://issues.apache.org/jira/browse/HAWQ-178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15135133#comment-15135133
]
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_r52079820
--- Diff:
pxf/pxf-json/src/main/java/org/apache/hawq/pxf/plugins/json/JsonResolver.java
---
@@ -0,0 +1,252 @@
+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.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+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.JsonFactory;
+import org.codehaus.jackson.JsonNode;
+import org.codehaus.jackson.map.ObjectMapper;
+
+/**
+ * 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 static final Log LOG = LogFactory.getLog(JsonResolver.class);
+
+ private ArrayList<OneField> oneFieldList;
+ private ColumnDescriptorCache[] columnDescriptorCache;
+ private ObjectMapper mapper;
+
+ /**
+ * Row with empty fields. Returned in case of broken or malformed json
records.
+ */
+ private final List<OneField> emptyRow;
+
+ public JsonResolver(InputData inputData) throws Exception {
+ super(inputData);
+ oneFieldList = new ArrayList<OneField>();
+ mapper = new ObjectMapper(new JsonFactory());
+
+ // Precompute the column metadata. The metadata is used for
mapping column names to json nodes.
+ columnDescriptorCache = new
ColumnDescriptorCache[inputData.getColumns()];
+ for (int i = 0; i < inputData.getColumns(); ++i) {
+ ColumnDescriptor cd = inputData.getColumn(i);
+ columnDescriptorCache[i] = new
ColumnDescriptorCache(cd);
+ }
+
+ emptyRow = createEmptyRow();
+ }
+
+ @Override
+ public List<OneField> getFields(OneRow row) throws Exception {
+ oneFieldList.clear();
+
+ String jsonRecordAsText = row.getData().toString();
+
+ JsonNode root = decodeLineToJsonNode(jsonRecordAsText);
+
+ if (root == null) {
+ LOG.warn("Return empty-fields row due to invalid JSON:
" + jsonRecordAsText);
+ return emptyRow;
+ }
+
+ // Iterate through the column definition and fetch our JSON data
+ for (ColumnDescriptorCache columnMetadata :
columnDescriptorCache) {
+
+ JsonNode node = getChildJsonNode(root,
columnMetadata.getNormalizedProjections());
+
+ // If this node is null or missing, add a null value
here
+ if (node == null || node.isMissingNode()) {
+ addNullField(columnMetadata.getColumnType());
+ } else if (columnMetadata.isArray()) {
+ // If this column is an array index, ex.
"tweet.hashtags[0]"
+ if (node.isArray()) {
+ // If the JSON node is an array, then
add it to our list
+
addFieldFromJsonArray(columnMetadata.getColumnType(), node,
columnMetadata.getArrayNodeIndex());
+ } else {
+ throw new
IllegalStateException(columnMetadata.getColumnName() + " is not an array node");
+ }
+ } else {
+ // This column is not an array type
+ // Add the value to the record
+
addFieldFromJsonNode(columnMetadata.getColumnType(), node);
+ }
+ }
+
+ return oneFieldList;
+ }
+
+ /**
+ * @return Returns a row comprised of typed, empty fields. Used as a
result of broken/malformed json records.
+ */
+ private List<OneField> createEmptyRow() {
+ ArrayList<OneField> emptyFieldList = new ArrayList<OneField>();
+ for (ColumnDescriptorCache column : columnDescriptorCache) {
+ emptyFieldList.add(new
OneField(column.getColumnType().getOID(), null));
+ }
+ return emptyFieldList;
+ }
+
+ /**
+ * Iterates down the root node to the child JSON node defined by the
projs path.
+ *
+ * @param root
+ * node to to start the traversal from.
+ * @param projs
+ * defines the path from the root to the desired child node.
+ * @return Returns the child node defined by the root and projs path.
+ */
+ private JsonNode getChildJsonNode(JsonNode root, String[] projs) {
+
+ // Iterate through all the tokens to the desired JSON node
+ JsonNode node = root;
+ for (int j = 0; j < projs.length; ++j) {
+ node = node.path(projs[j]);
+ }
+
+ return node;
+ }
+
+ /**
+ * Iterates through the given JSON node to the proper index and adds
the field of corresponding type
+ *
+ * @param type
+ * The {@link DataType} type
+ * @param node
+ * The JSON array node
+ * @param index
+ * The array index to iterate to
+ * @throws IOException
+ */
+ private void addFieldFromJsonArray(DataType type, JsonNode node, int
index) throws IOException {
+
+ int count = 0;
+ boolean added = false;
+ for (Iterator<JsonNode> arrayNodes = node.getElements();
arrayNodes.hasNext();) {
+ JsonNode arrayNode = arrayNodes.next();
+
+ if (count == index) {
+ added = true;
+ addFieldFromJsonNode(type, arrayNode);
+ break;
+ }
+
+ ++count;
+ }
+
+ // if we reached the end of the array without adding a field,
add null
+ if (!added) {
+ addNullField(type);
+ }
+ }
+
+ /**
+ * Adds a field from a given JSON node value based on the {@link
DataType} type.
+ *
+ * @param type
+ * The DataType type
+ * @param val
+ * The JSON node to extract the value.
+ * @throws IOException
+ */
+ private void addFieldFromJsonNode(DataType type, JsonNode val) throws
IOException {
+ OneField oneField = new OneField();
+ oneField.type = type.getOID();
+
+ if (val.isNull()) {
+ oneField.val = null;
+ } else {
+ switch (type) {
+ case BIGINT:
+ oneField.val = val.asLong();
+ break;
+ case BOOLEAN:
+ oneField.val = val.asBoolean();
+ break;
+ case CHAR:
+ oneField.val = val.asText().charAt(0);
+ break;
+ case BYTEA:
+ oneField.val = val.asText().getBytes();
+ break;
+ case FLOAT8:
+ case REAL:
+ oneField.val = val.asDouble();
+ break;
+ case INTEGER:
+ case SMALLINT:
+ oneField.val = val.asInt();
+ break;
+ case BPCHAR:
+ case TEXT:
+ case VARCHAR:
+ oneField.val = val.asText();
+ break;
+ default:
+ throw new IOException("Unsupported type " +
type);
+ }
+ }
+
+ oneFieldList.add(oneField);
+ }
+
+ /**
+ * Adds a null field of the given type.
+ *
+ * @param type
+ * The {@link DataType} type
+ */
+ private void addNullField(DataType type) {
+ oneFieldList.add(new OneField(type.getOID(), null));
+ }
+
+ /**
+ * Converts the input line parameter into {@link JsonNode} instance.
+ *
+ * @param line
+ * JSON text
+ * @return Returns a {@link JsonNode} that represents the input line or
null for invalid json.
+ */
+ private JsonNode decodeLineToJsonNode(String line) {
+
+ try {
+ return mapper.readTree(line);
+ } catch (Exception e) {
+ LOG.error("Failed to pars JSON object", e);
--- End diff --
typo parse
> 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: Christian Tzolov
> Fix For: backlog
>
> Attachments: PXFJSONPluginforHAWQ2.0andPXF3.0.0.pdf,
> PXFJSONPluginforHAWQ2.0andPXF3.0.0v.2.pdf,
> PXFJSONPluginforHAWQ2.0andPXF3.0.0v.3.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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