Addresses issues with duckdb use of delta encodings (#77)

* Addresses issues with duckdb use of delta encodings

* Shrunk size of test data

src/datapage.js

@@ -48,6 +48,13 @@ export function readDataPage(bytes, daph, { type, element, schemaPath }) {
     }
   } else if (daph.encoding === 'BYTE_STREAM_SPLIT') {
     dataPage = byteStreamSplit(reader, nValues, type, element.type_length)
+  } else if (daph.encoding === 'DELTA_BINARY_PACKED') {
+    const int32 = type === 'INT32'
+    dataPage = int32 ? new Int32Array(nValues) : new BigInt64Array(nValues)
+    deltaBinaryUnpack(reader, nValues, dataPage)
+  } else if (daph.encoding === 'DELTA_LENGTH_BYTE_ARRAY') {
+    dataPage = new Array(nValues)
+    deltaLengthByteArray(reader, nValues, dataPage)
   } else {
     throw new Error(`parquet unsupported encoding: ${daph.encoding}`)
   }

test/files/duckdb_delta_binary_packed.metadata.json

@@ -0,0 +1,48 @@
+{
+  "version": 1,
+  "schema": [
+    {
+      "repetition_type": "REQUIRED",
+      "name": "duckdb_schema",
+      "num_children": 1
+    },
+    {
+      "type": "INT64",
+      "repetition_type": "OPTIONAL",
+      "name": "range",
+      "converted_type": "INT_64"
+    }
+  ],
+  "num_rows": 1250,
+  "row_groups": [
+    {
+      "columns": [
+        {
+          "file_offset": 0,
+          "meta_data": {
+            "type": "INT64",
+            "encodings": ["DELTA_BINARY_PACKED"],
+            "path_in_schema": ["range"],
+            "codec": "SNAPPY",
+            "num_values": 1250,
+            "total_uncompressed_size": 40,
+            "total_compressed_size": 42,
+            "data_page_offset": 4,
+            "statistics": {
+              "max": 1249,
+              "min": 0,
+              "null_count": 0,
+              "max_value": 1249,
+              "min_value": 0
+            }
+          }
+        }
+      ],
+      "total_byte_size": 40,
+      "num_rows": 1250,
+      "file_offset": 4
+    }
+  ],
+  "created_by": "DuckDB version v1.2.1 (build 8e52ec4395)",
+  "metadata_length": 169
+}

test/files/duckdb_delta_length_byte_array.metadata.json

@@ -0,0 +1,48 @@
+{
+  "version": 1,
+  "schema": [
+    {
+      "repetition_type": "REQUIRED",
+      "name": "duckdb_schema",
+      "num_children": 1
+    },
+    {
+      "type": "BYTE_ARRAY",
+      "repetition_type": "OPTIONAL",
+      "name": "range_varchar",
+      "converted_type": "UTF8"
+    }
+  ],
+  "num_rows": 1250,
+  "row_groups": [
+    {
+      "columns": [
+        {
+          "file_offset": 0,
+          "meta_data": {
+            "type": "BYTE_ARRAY",
+            "encodings": ["DELTA_LENGTH_BYTE_ARRAY"],
+            "path_in_schema": ["range_varchar"],
+            "codec": "SNAPPY",
+            "num_values": 1250,
+            "total_uncompressed_size": 3996,
+            "total_compressed_size": 3390,
+            "data_page_offset": 4,
+            "statistics": {
+              "max": "999",
+              "min": "0",
+              "null_count": 0,
+              "max_value": "999",
+              "min_value": "0"
+            }
+          }
+        }
+      ],
+      "total_byte_size": 3996,
+      "num_rows": 1250,
+      "file_offset": 4
+    }
+  ],
+  "created_by": "DuckDB version v1.2.1 (build 8e52ec4395)",
+  "metadata_length": 164
+}