[GitHub] [calcite] michaelmior commented on a change in pull request #1302: [CALCITE-3176] File adapter for parsing JSON files

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michaelmior commented on a change in pull request #1302: [CALCITE-3176] File adapter for parsing JSON files
URL: https://github.com/apache/calcite/pull/1302#discussion_r305410450
 
 

 ##########
 File path: example/csv/src/main/java/org/apache/calcite/adapter/csv/JsonTable.java
 ##########
 @@ -16,46 +16,91 @@
  */
 package org.apache.calcite.adapter.csv;
 
-import org.apache.calcite.DataContext;
-import org.apache.calcite.linq4j.AbstractEnumerable;
-import org.apache.calcite.linq4j.Enumerable;
-import org.apache.calcite.linq4j.Enumerator;
 import org.apache.calcite.rel.type.RelDataType;
 import org.apache.calcite.rel.type.RelDataTypeFactory;
-import org.apache.calcite.schema.ScannableTable;
+import org.apache.calcite.schema.Statistic;
+import org.apache.calcite.schema.Statistics;
 import org.apache.calcite.schema.impl.AbstractTable;
-import org.apache.calcite.sql.type.SqlTypeName;
+import org.apache.calcite.util.Pair;
 import org.apache.calcite.util.Source;
 
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.exc.MismatchedInputException;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
 /**
  * Table based on a JSON file.
  */
-public class JsonTable extends AbstractTable implements ScannableTable {
-  private final Source source;
+public class JsonTable extends AbstractTable {
+  private final ObjectMapper objectMapper = new ObjectMapper();
+  protected final List<Object> list;
+
+  private LinkedHashMap<String, Object> jsonFieldMap = new LinkedHashMap<>(1);
 
-  /** Creates a JsonTable. */
   public JsonTable(Source source) {
-    this.source = source;
-  }
+    Object jsonObj = null;
+    try {
+      objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true)
+          .configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true)
+          .configure(JsonParser.Feature.ALLOW_COMMENTS, true);
+      if (source.file().exists() && source.file().length() > 0) {
+        if ("file".equals(source.protocol())) {
+          //noinspection unchecked
+          jsonObj = objectMapper.readValue(source.file(), Object.class);
+        } else {
+          //noinspection unchecked
+          jsonObj = objectMapper.readValue(source.url(), Object.class);
+        }
+      }
+    } catch (MismatchedInputException e) {
+      if (!e.getMessage().contains("No content")) {
+        throw new RuntimeException(e);
+      }
+    } catch (Exception e) {
+      throw new RuntimeException(e);
+    }
 
-  public String toString() {
-    return "JsonTable";
+    if (jsonObj == null) {
+      list = new ArrayList<>();
+      jsonFieldMap.put("EmptyFileHasNoColumns", Boolean.TRUE);
 
 Review comment:
   I haven't tested this, but is it not possible to actually have a table with no columns?

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