Add example binary variant data and regeneration scripts

.gitignore

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+.idea
+variant/derby.log

README.md

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   ~ under the License.
   -->
 # Testing Data and Utilities for Apache Parquet
+
+- [data](data/README.md) - Sample Parquet data files for testing
+- [bad_data](bad_data/README.md) - Reproducers for bad data files for testing
+- [variant](variant/README.md) - Sample [Variant] binary values
+
+
+[Variant]: https://github.com/apache/parquet-format/blob/master/VariantEncoding.md

variant/.gitignore

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+derby.log
+spark-warehouse
+metastore_db

variant/README.md

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+<!--
+  ~ 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.
+  -->
+
+# Variant Binary Encoding
+
+This directory contains binary artifacts encoded using the Parquet  [Variant]
+binary encoding. These files are **not** valid Parquet files, but rather
+raw binary data.
+
+## Structure
+
+* `data_dictionary.json` - contains the JSON representation of each of the examples
+
+Each example consists of 2 files:
+
+* `.metadata` -- the binary contents of the `metadata` field
+* `.value` -- the binary contents of the `value` field
+
+## Descriptions
+
+1. `primitive_<type>` -- Examples primitive (`basic_type` = 1), one for each of the [primitive types listed in the spec]
+2. `short_string` -- Example of short string (`basic_type` = 2)
+3. `object_empty` -- Example of object (`basic_type` = 3) with no fields
+3. `object_primitive` -- Example of object with only primitive fields
+4. `object_nested` -- Example of object with other objects in fields 
+5. `array_empty` -- Example of array (`basic_type` = 4) with no elements
+5. `array_primitive` -- Example of array with only primitive elements
+6. `array_nested` -- Example of an with objects and other arrays in the elements
+
+
+## Regenerating these files
+
+The files were generated by running the [`regen.py`](regen.py) script that uses Apache Spark to 
+generate the files. 
+
+
+
+
+[Variant]: https://github.com/apache/parquet-format/blob/master/VariantEncoding.md
+[primitive types listed in the spec]: https://github.com/apache/parquet-format/blob/master/VariantEncoding.md#value-data-for-primitive-type-basic_type0

variant/data_dictionary.json

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+{
+    "array_primitive": [
+        2,
+        1,
+        5,
+        9
+    ],
+    "primitive_binary": "AxM33q2+78r+",
+    "primitive_timestampntz": "2025-04-16 12:34:56.78",
+    "primitive_timestamp": "2025-04-16 12:34:56.78-04:00",
+    "primitive_float": 1234567940.0,
+    "primitive_int32": 123456,
+    "short_string": "Less than 64 bytes (\u2764\ufe0f with utf8)",
+    "primitive_decimal16": 1.2345678912345678e+16,
+    "primitive_int64": 12345678,
+    "primitive_int16": 1234,
+    "primitive_decimal8": 12345678.9,
+    "primitive_double": 1234567890.1234,
+    "object_primitive": {
+        "boolean_false_field": false,
+        "boolean_true_field": true,
+        "double_field": 1.23456789,
+        "int_field": 1,
+        "null_field": null,
+        "string_field": "Apache Parquet",
+        "timestamp_field": "2025-04-16T12:34:56.78"
+    },
+    "primitive_string": "This string is longer than 64 bytes and therefore does not fit in a short_string and it also includes several non ascii characters such as \ud83d\udc22, \ud83d\udc96, \u2665\ufe0f, \ud83c\udfa3 and \ud83e\udd26!!",
+    "primitive_boolean_true": true,
+    "primitive_date": "2025-04-16",
+    "primitive_int8": 42,
+    "object_empty": {},
+    "primitive_boolean_false": false,
+    "primitive_decimal4": 12.34,
+    "array_empty": [],
+    "primitive_null": null,
+    "object_nested": {
+        "id": 1,
+        "observation": {
+            "location": "In the Volcano",
+            "time": "12:34:56",
+            "value": {
+                "humidity": 456,
+                "temperature": 123
+            }
+        },
+        "species": {
+            "name": "lava monster",
+            "population": 12345
+        }
+    },
+    "array_nested": [
+        {
+            "id": 1,
+            "thing": {
+                "names": [
+                    "Contrarian",
+                    "Spider"
+                ]
+            }
+        },
+        {
+            "id": 2,
+            "names": [
+                "Apple",
+                "Ray",
+                null
+            ],
+            "type": "if"
+        }
+    ]
+}

variant/primitive_boolean_false.value

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+

variant/primitive_boolean_true.value

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+

variant/primitive_double.value

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+�凴�e�A

variant/primitive_float.value

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+8,�N

variant/primitive_int16.value

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+�

variant/primitive_int8.value

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+*

variant/regen.py

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+# 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.
+
+# This program uses Apache Spark to generate example binary Variant data
+#
+# Requirements
+# pip install pyarrow
+# pip install pyspark
+#
+# Last run with Spark 4.0 preview 2:
+# https://spark.apache.org/news/spark-4.0.0-preview2.html
+
+from pyspark.sql import SparkSession
+import pyarrow.parquet as pq
+import os
+import json
+
+# Initialize Spark session and create variant data via SQL
+spark = SparkSession.builder \
+    .appName("PySpark SQL Example") \
+    .getOrCreate()
+
+# recursively cleanup the spark-warehouse directory
+if os.path.exists('spark-warehouse'):
+    for root, dirs, files in os.walk('spark-warehouse', topdown=False):
+        for name in files:
+            os.remove(os.path.join(root, name))
+        for name in dirs:
+            os.rmdir(os.path.join(root, name))
+
+
+# Create a table with variant and insert various types into it
+#
+# This writes data files into spark-warehouse/output
+sql = """
+CREATE TABLE T (name VARCHAR(2000), variant_col VARIANT);
+
+-------------------------------
+-- Primitive type (basic_type=0)
+-------------------------------
+-- One row with a value from each type listed in 
+-- https://github.com/apache/parquet-format/blob/master/VariantEncoding.md#encoding-types
+--
+-- Spark Types: https://spark.apache.org/docs/latest/sql-ref-datatypes.html
+-- Note: use  explicit typecasts as spark returns an error for implicit casts
+INSERT INTO T VALUES ('primitive_null', NULL);
+INSERT INTO T VALUES ('primitive_boolean_true', true::Variant);
+INSERT INTO T VALUES ('primitive_boolean_false', false::Variant);
+INSERT INTO T VALUES ('primitive_int8', 42::Byte::Variant);
+INSERT INTO T VALUES ('primitive_int16', 1234::Short::Variant);
+INSERT INTO T VALUES ('primitive_int32', 123456::Integer::Variant);
+INSERT INTO T VALUES ('primitive_int64', 12345678::Long::Variant);
+INSERT INTO T VALUES ('primitive_double', 1234567890.1234::Double::Variant);
+INSERT INTO T VALUES ('primitive_decimal4', 12.34::Decimal(8,2)::Variant);
+INSERT INTO T VALUES ('primitive_decimal8', 12345678.90::Decimal(12,2)::Variant);
+INSERT INTO T VALUES ('primitive_decimal16', 12345678912345678.90::Decimal(30,2)::Variant);
+INSERT INTO T VALUES ('primitive_date', '2025-04-16'::Date::Variant);
+INSERT INTO T VALUES ('primitive_timestamp', '2025-04-16T12:34:56.78'::Timestamp::Variant);
+INSERT INTO T VALUES ('primitive_timestampntz', '2025-04-16T12:34:56.78'::Timestamp_NTZ::Variant);
+INSERT INTO T VALUES ('primitive_float', 1234567890.1234::Float::Variant);
+INSERT INTO T VALUES ('primitive_binary', X'31337deadbeefcafe'::Variant);
+INSERT INTO T VALUES ('primitive_string', 'This string is longer than 64 bytes and therefore does not fit in a short_string and it also includes several non ascii characters such as 🐢, 💖, ♥️, 🎣 and 🤦!!'::Variant);
+-- It is not clear how to create these types using Spark SQL
+-- TODO TimeNTZ                    (Type ID 17)
+-- TODO 'timestamp with timezone'  (Type ID 18)
+-- TODO 'timestamp with time zone' (Type ID 19)
+-- TODO 'UUID'                     (Type ID 20)
+
+-------------------------------
+-- Short string (basic_type=1)
+-------------------------------
+INSERT INTO T VALUES ('short_string', 'Less than 64 bytes (❤️ with utf8)'::Variant);
+
+-------------------------------
+-- Object (basic_type=2)
+-------------------------------
+-- Use parse_json to create Variant, as spark does not seem to support casting structs --> Variant.
+-- TODO create example variant objects with fields that have more specific types (like timestamp, date, etc)
+--   cannot cast "STRUCT<...>" to "VARIANT""
+-- INSERT INTO T VALUES ('object_primitive', struct(1234.56::Double as double_field, true as boolean_true_field, false as boolean_false_field, '2025-04-16T12:34:56.78'::Timestamp as timestamp_field, 'Apache Parquet' as string_field, null as null_field)::Variant);
+INSERT INTO T VALUES ('object_empty', parse_json('{}')::Variant);
+INSERT INTO T VALUES ('object_primitive', parse_json('{"int_field" : 1, "double_field": 1.23456789, "boolean_true_field": true, "boolean_false_field": false, "string_field": "Apache Parquet", "null_field": null, "timestamp_field": "2025-04-16T12:34:56.78"}')::Variant);
+INSERT INTO T VALUES ('object_nested', parse_json('{ "id" : 1, "species" : { "name": "lava monster", "population": 12345}, "observation" : { "time": "12:34:56", "location": "In the Volcano", "value" : { "temperature": 123, "humidity": 456 } } }')::Variant);
+
+--TODO objects with more than 2**8 distinct fields (that require using more than one byte for field offset)
+--TODO objects with more than 2**16 distinct fields (that require using more than 2 bytes for field offset)
+--TODO objects with more than 2**24 distinct fields (that require using more than 3 bytes for field offset)
+
+-------------------------------
+-- Array (basic_type=3)
+-------------------------------
+INSERT INTO T VALUES ('array_empty', parse_json('[]')::Variant);
+INSERT INTO T VALUES ('array_primitive', parse_json('[2, 1, 5, 9]')::Variant);
+INSERT INTO T VALUES ('array_nested', parse_json('[ { "id": 1, "thing": { "names": ["Contrarian", "Spider"] } }, { "id": 2, "type": "if", "names": ["Apple", "Ray", null] } ]')::Variant);
+
+-- TODO arrays with more than 2**8 distinct elements (that require using more than one byte for count)
+-- TODO arrays where the total length of all values is greater than 2**8, 2**16, and 2**24 bytes (requires using more than one byte for the offsets)
+
+
+-- Copy the output to a new table that also has the JSON representation of the variant column
+DROP TABLE IF EXISTS output;
+CREATE TABLE output AS SELECT name, variant_col, to_json(variant_col) as json_col FROM T;
+"""
+for statement in sql.split("\n"):
+    statement = statement.strip()
+    if not statement or statement.startswith("--"):
+        continue
+    print("Running SQL:", statement)
+    spark.sql(statement)
+
+mypath = 'spark-warehouse/output'
+parquet_files = [f for f in os.listdir(mypath) if f.endswith('.parquet')]
+
+# extract the values from the parquet files
+data_dictionary = {}
+for f in parquet_files:
+    table = pq.read_table(os.path.join(mypath, f))
+    for row in range(len(table)):
+        name = table[0][row]
+        # variants are stored as StructArrays with two fields:
+        # metadata, and value
+        variant_col = table[1][row]
+        metadata = variant_col['metadata']
+        value = variant_col['value']
+        json_value = table[2][row]
+
+        print("Writing metadata for", name)
+
+        # write the metadata, value, and json representation to files
+        with open(f"{name}.metadata", "wb") as f:
+            buffer = metadata.as_buffer()
+            if buffer is not None:
+                f.write(buffer)
+        with open(f"{name}.value", "wb") as f:
+            buffer = value.as_buffer()
+            if buffer is not None:
+                f.write(buffer)
+
+        # Add the JSON representation to the data dictionary
+        name = name.as_py()
+        json_value = json_value.as_py()
+
+        if json_value is not None:
+            data_dictionary[name] = json.loads(json_value)
+        else:
+            data_dictionary[name] = None
+
+with open(f"data_dictionary.json", "w") as f:
+    f.write(json.dumps(data_dictionary, indent=4))
+

variant/short_string.value

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+�Less than 64 bytes (❤️ with utf8)