Example 04: CSV Import - Tables (Documents)

View source code

Production-ready CSV import with automatic type inference, NULL handling, and index optimization

Overview

This example demonstrates importing real-world CSV data from the MovieLens dataset into ArcadeDB documents. You'll learn production-ready patterns for:

• Automatic type inference - Java analyzes CSV and infers optimal ArcadeDB types
• Schema-on-write - Database creates schema automatically during import
• NULL value handling - Import and query missing data across all types
• Batch processing - Optimize import performance with commit batching
• Index optimization - Create indexes AFTER import for maximum throughput
• Performance analysis - Measure query speedup with statistical validation
• Result validation - Verify indexes return identical results with actual data samples

What You'll Learn

• Automatic type inference by Java CSV importer (LONG, DOUBLE, STRING)
• Schema-on-write during import (no manual schema creation needed)
• NULL value import from empty CSV cells
• Query performance measurement (10 runs with statistics)
• Index creation timing (before vs after import)
• Composite indexes for multi-column queries
• Result validation with actual data samples
• Production import patterns for large datasets

Prerequisites

1. Install ArcadeDB Python bindings:

uv pip install arcadedb-embedded

2. Dataset download (automatic):

The example automatically downloads the dataset if it doesn't exist. You can also download it manually:

cd bindings/python/examples
python download_data.py movielens-large # movielens large dataset
python download_data.py movielens-small # movielens small dataset

Two dataset sizes available:

• movielens-large: ~86,000 movies, ~33M ratings (~265 MB) - Realistic performance testing
• movielens-small: ~9,700 movies, ~100,000 ratings (~1 MB) - Quick testing

Both datasets include intentional NULL values for testing:

• movies.csv: ~3% NULL genres
• ratings.csv: ~2% NULL timestamps
• links.csv: ~10% NULL imdbId, ~15% NULL tmdbId
• tags.csv: ~5% NULL tags

Dataset Structure

MovieLens Large - 4 CSV files:

File	Records	Columns	Description
movies.csv	86,537	movieId, title, genres	Movie metadata
ratings.csv	33,832,162	userId, movieId, rating, timestamp	User ratings
links.csv	86,537	movieId, imdbId, tmdbId	External IDs (with NULLs)
tags.csv	2,328,315	userId, movieId, tag, timestamp	User tags (with NULLs)

Total records: 36,333,551 documents

For quick testing with the smaller dataset (124,003 records), use: python download_data.py movielens-small

Usage

# Basic usage (large dataset by default)
python 04_csv_import_documents.py

# Use small dataset for quick testing
python 04_csv_import_documents.py --size small

# Configure parallel threads and batch size
python 04_csv_import_documents.py --parallel 8 --batch-size 10000

# Export database for reproducibility
python 04_csv_import_documents.py --export

# See all options
python 04_csv_import_documents.py --help

Key options:

• --size {small,large} - Dataset size (default: large)
• --parallel PARALLEL - Number of parallel import threads (default: auto-detect)
• --batch-size BATCH_SIZE - Records per commit batch (default: 5000)
• --export - Export database to JSONL after import
• --db-name DB_NAME - Custom database name (default: movielens_{size}_db)

Recommendations:

• Parallel threads: 4-8 for best performance (auto-detected by default)
• Batch size: 5000-50000 (larger = faster imports, more memory)
• Export: Use --export to create reproducible benchmark databases

Type Inference by Java

The example uses automatic type inference by the Java CSV importer, which analyzes the data and selects optimal ArcadeDB types:

Example Inference Results (movielens-large)

📋 Movie (movies.csv):
   • movieId: LONG (e.g., '1')
   • title: STRING (e.g., 'Toy Story (1995)')
   • genres: STRING (e.g., 'Adventure|Animation|Children|Comedy|Fantasy')

📋 Rating (ratings.csv):
   • userId: LONG (e.g., '1')
   • movieId: LONG (e.g., '1')
   • rating: DOUBLE (e.g., '4.0')
   • timestamp: LONG (e.g., '964982703')

📋 Link (links.csv):
   • movieId: LONG (e.g., '1')
   • imdbId: LONG (e.g., '')         ← NULL value
   • tmdbId: LONG (e.g., '862')

📋 Tag (tags.csv):
   • userId: LONG (e.g., '2')
   • movieId: LONG (e.g., '60756')
   • tag: STRING (e.g., 'funny')
   • timestamp: LONG (e.g., '1445714994')

Code Walkthrough

Step 1: Check Dataset Availability

data_dir = Path(__file__).parent / "data" / "ml-latest-small"
if not data_dir.exists():
    print("❌ MovieLens dataset not found!")
    print("💡 Please download the dataset first:")
    print("   python download_data.py")
    exit(1)

Step 2: Let Java Infer Types Automatically

The Java CSV importer automatically analyzes the CSV data and infers optimal ArcadeDB types (LONG, DOUBLE, STRING). No manual type inference code is needed - the importer handles this intelligently based on the actual data values.

The schema is created automatically during import (schema-on-write), eliminating the need for explicit schema definition before import.

Step 3: Import CSV Files Directly

# Import with batch commits for performance
import_options = {
    "commit_every": args.batch_size,  # Batch size for commits
}
stats = arcadedb.import_csv(db, movies_csv, "Movie", **import_options)

# Check for NULL values (using .first() for efficiency)
null_genres = (
    db.query("sql", "SELECT count(*) as c FROM Movie WHERE genres IS NULL")
    .first()
    .get("c")
)

if null_genres > 0:
    print(f"   🔍 NULL values detected:")
    print(f"      • genres: {null_genres:,} NULL values ({null_genres/stats['documents']*100:.1f}%)")
    print("   💡 Empty CSV cells correctly imported as SQL NULL")

Performance results (small dataset):

• Movies: 105,891 records/sec
• Ratings: 484,788 records/sec (largest file, highly optimized)
• Links: 374,692 records/sec
• Tags: 167,409 records/sec
• Total: 356,330 records/sec average

Performance results (large dataset):

• Movies: 288,457 records/sec
• Ratings: 908,832 records/sec (largest file, highly optimized)
• Links: 697,879 records/sec
• Tags: 739,148 records/sec
• Total: 890,528 records/sec average

Key insight: Larger datasets show better performance due to more efficient batch processing and reduced per-record overhead.

Step 8: Query Performance WITHOUT Indexes

test_queries = [
    ("Find movie by ID", "SELECT FROM Movie WHERE movieId = 500"),
    ("Find user's ratings", "SELECT FROM Rating WHERE userId = 414 ORDER BY movieId, rating LIMIT 10"),
    ("Find movie ratings", "SELECT FROM Rating WHERE movieId = 500 ORDER BY userId, rating LIMIT 10"),
    ("Count user's ratings", "SELECT count(*) as count FROM Rating WHERE userId = 414"),
    ("Find movies by genre", "SELECT FROM Movie WHERE genres LIKE '%Action%' ORDER BY movieId LIMIT 10"),
]

# Run each query 10 times for statistical reliability
for query_name, query in test_queries:
    run_times = []
    for _ in range(10):
        query_start = time.time()
        result = list(db.query("sql", query))
        run_times.append(time.time() - query_start)

    avg_time = statistics.mean(run_times)
    std_time = statistics.stdev(run_times)
    print(f"   📊 {query_name}:")
    print(f"      Average: {avg_time*1000:.2f}ms ± {std_time*1000:.2f}ms")

Step 9: Create Indexes (AFTER Import)

db.schema.create_index("Movie", ["movieId"], unique=True)
db.schema.create_index("Rating", ["userId", "movieId"], unique=False)  # Composite!
db.schema.create_index("Link", ["movieId"], unique=True)
db.schema.create_index("Tag", ["movieId"], unique=False)

Why create indexes AFTER import?

• 2-3x faster total time
• Indexes built in one pass
• Fully compacted from start
• Production best practice

Step 10: Query Performance WITH Indexes

Same queries, now with indexes active. Results show dramatic speedup!

Performance Results

Query Speedup Summary

🚀 Performance Improvement Summary:
======================================================================
Query                          Before (ms)     After (ms)      Speedup
======================================================================
Find movie by ID               39.1±7.6        0.7±1.9         58.1x
                                     (98.3% time saved)
Find user's ratings            16003.9±79.4    1.1±0.4         14,836x
                                     (100.0% time saved)
Find movie ratings             16524.8±124.2   153.1±22.2      107.9x
                                     (99.1% time saved)
Count user's ratings           16004.3±138.3   0.8±1.4         19,604x
                                     (100.0% time saved)
Find movies by genre           1.0±1.0         0.8±0.3         1.3x
                                     (23.7% time saved)
Count ALL Action movies        58.7±8.4        65.1±18.0       0.9x
                                     (-10.8% time saved)
======================================================================

Key findings:

• ✅ Composite indexes show massive gains (up to 19,604x speedup!)
• ✅ Single column lookups are very fast (58.1x speedup)
• ✅ Standard deviation shows query stability

NULL Value Handling

The example demonstrates comprehensive NULL handling:

Import Results

Step 2: Importing movies.csv → Movie documents...
   ✅ Imported 86,537 movies
   🔍 NULL values detected:
      • genres: 2,584 NULL values (3.0%)
   💡 Empty CSV cells correctly imported as SQL NULL

Step 4: Importing ratings.csv → Rating documents...
   ✅ Imported 33,832,162 ratings
   🔍 NULL values detected:
      • timestamp: 675,782 NULL values (2.0%)
   💡 Empty CSV cells correctly imported as SQL NULL

Step 5: Importing links.csv → Link documents...
   ✅ Imported 86,537 links
   🔍 NULL values detected:
      • imdbId: 8,628 NULL values (10.0%)
      • tmdbId: 13,026 NULL values (15.1%)
   💡 Empty CSV cells correctly imported as SQL NULL

Step 6: Importing tags.csv → Tag documents...
   ✅ Imported 2,328,315 tags
   🔍 NULL values detected:
      • tag: 116,644 NULL values (5.0%)
   💡 Empty CSV cells correctly imported as SQL NULL

NULL Values in Aggregations

💬 Top 10 most common tags:
    1. 'None' (116,644 uses)          ← NULL tags appear as 'None'
    2. 'sci-fi' (13,612 uses)
    ...

🎭 Top 10 genres by movie count:
    1. Drama (11,857 movies)
    ...
    6. None (2,584 movies)          ← NULL genres appear as 'None'

Total NULL values: ~799,638 across all fields (LONG and STRING types)

Index Architecture

ArcadeDB uses LSM-Tree (Log-Structured Merge Tree) for all indexes - a single unified backend that handles all data types efficiently.

How LSM-Tree Works

Architecture:

LSMTreeIndex
├── Mutable Buffer (in-memory)
│   └── Recent writes, fast inserts
│
└── Compacted Storage (disk)
    └── Sorted, immutable data

Key advantages:

• Write-optimized: Sequential writes to memory buffer (perfect for bulk imports)
• Type-agnostic: Same structure for all types, type-aware comparison during lookups
• Auto-compaction: Background merging keeps data sorted and compact
• Transaction-friendly: Buffers writes until commit

Type Performance & Storage

Binary serialization per type:

Type	Storage Size	Comparison Speed	Best For
BYTE	1 byte	⚡ Very fast	Flags, small counts (0-255)
SHORT	2 bytes	⚡ Very fast	Medium numbers (-32K to 32K)
INTEGER	4 bytes	⚡ Very fast	IDs, standard numbers (up to 2B)
LONG	8 bytes	⚡ Very fast	Large IDs, timestamps
FLOAT	4 bytes	⚡ Fast	Small decimals (7-digit precision)
DOUBLE	8 bytes	⚡ Fast	Standard decimals (15-digit precision)
DATE/DATETIME	8 bytes (as LONG)	⚡ Fast	Timestamps, dates
STRING	Variable	🐌 Slower	Text, byte-by-byte comparison
DECIMAL	Variable	🐌 Slowest	Exact precision (e.g., money)

Index space example (100K records):

• BYTE: 100KB | SHORT: 200KB | INTEGER: 400KB (best balance) | LONG: 800KB | STRING(20): 2MB+

Why this matters:

• Smaller types = more keys per page = better cache performance
• Fixed-size types = faster comparison = better query speed
• Choose INTEGER for most IDs (handles 2 billion values, compact, fast)

Analysis Queries

The example includes comprehensive data analysis:

Record Counts

SELECT count(*) as count FROM Movie     # 9,742 movies
SELECT count(*) as count FROM Rating    # 100,836 ratings
SELECT count(*) as count FROM Link      # 9,742 links
SELECT count(*) as count FROM Tag       # 3,683 tags

Rating Statistics

SELECT
    count(*) as total_ratings,
    avg(rating) as avg_rating,
    min(rating) as min_rating,
    max(rating) as max_rating
FROM Rating

# Results: 100,836 ratings, avg 3.50 ★, range 0.5-5.0

Rating Distribution

SELECT rating, count(*) as count
FROM Rating
GROUP BY rating
ORDER BY rating

# Results:
# 0.5 ★ : 1,370
# 1.0 ★ : 2,811
# ...
# 4.0 ★ : 26,818  (most common)
# 5.0 ★ : 13,211

Top Genres

SELECT genres, count(*) as count
FROM Movie
WHERE genres <> '(no genres listed)'
GROUP BY genres
ORDER BY count DESC
LIMIT 10

# Results: Drama (1,022), Comedy (922), Comedy|Drama (429), ...

Most Active Users

SELECT userId, count(*) as rating_count
FROM Rating
GROUP BY userId
ORDER BY rating_count DESC
LIMIT 10

# Results: User 414 (2,698 ratings), User 599 (2,478), ...

Best Practices Demonstrated

✅ Type Inference by Java

• Java CSV importer automatically analyzes data and selects optimal types
• Handles LONG, DOUBLE, STRING intelligently based on actual values
• No manual type inference code needed
• Schema-on-write simplifies development

✅ Schema Definition

• Define schema BEFORE import (validation + optimization)
• Use explicit property types (no guessing)
• Choose appropriate types for data ranges

✅ Import Optimization

• Use commit_every parameter for batching
• Larger batches = faster imports (balance with memory)
• Movies: commit_every=1000 (smaller batches)
• Ratings: commit_every=5000 (larger dataset, bigger batches)

✅ Index Strategy

• CREATE INDEXES AFTER IMPORT (2-3x faster total time)
• Use composite indexes for multi-column queries
• Order matters: most selective column first
• Index creation timing: ~0.2 seconds for 124K records

✅ Performance Measurement

• Run queries 10 times for statistical reliability
• Calculate average, standard deviation, min, max
• Compare before/after index performance
• Measure speedup percentages

✅ NULL Handling

• Empty CSV cells → SQL NULL automatically
• Check NULL counts after import
• NULL values appear in aggregations (as 'None' string)
• Support NULL across all types (STRING, INTEGER, etc.)

Running the Example

cd bindings/python/examples

# Use default (large) dataset - downloads automatically if needed
python 04_csv_import_documents.py

# Use small dataset for quick testing - downloads automatically if needed
python 04_csv_import_documents.py --size small

# Use large dataset explicitly
python 04_csv_import_documents.py --size large

# With custom JVM heap for large datasets
ARCADEDB_JVM_ARGS="-Xmx8g -Xms8g" python 04_csv_import_documents.py --size large

Command-line options:

• --size {small,large} - Dataset size to use (default: large)
• The script automatically downloads the dataset if it doesn't exist

Expected output:

• Automatic dataset download if needed
• Step-by-step import progress
• NULL value detection for all 4 files
• Performance statistics (before/after indexes)
• Data analysis queries with results
• Total time: ~2-3 minutes (movielens-large) or ~5 seconds (movielens-small)

Database location:

• Small dataset: ./my_test_databases/movielens_small_db/
• Large dataset: ./my_test_databases/movielens_large_db/

The database is preserved for inspection after the example completes.

Database size:

• movielens-large: ~2.0 GB database from ~971 MB CSV files (~2.1x expansion)
• movielens-small: ~27 MB database from ~3.2 MB CSV files (~8.4x expansion)

⚠️ Note: Database files are larger than source CSVs due to:

• Index structures (LSM-Tree buffers and sorted data)
• Transaction logs and metadata
• Internal data structures for document storage
• WAL (Write-Ahead Log) files for durability

Key Takeaways

1. ✅ Automatic type inference by Java provides intelligent LONG/DOUBLE/STRING selection
2. ✅ Schema-on-write simplifies development (no manual schema creation needed)
3. ✅ NULL value handling works seamlessly across all data types (STRING, INTEGER, etc.)
4. ✅ Batch processing (commit_every) dramatically improves import performance
5. ✅ Create indexes AFTER import - 2-3x faster than indexing during import
6. ✅ LSM_TREE indexes provide massive performance gains (up to 14,836x speedup!)
7. ✅ Statistical validation (10 runs) ensures reliable performance measurements
8. ✅ Result validation compares actual data values, not just row counts
9. ✅ Multi-bucket architecture creates 15 buckets per type, 1 index file per bucket per property
10. ✅ Database persistence - reopen and query immediately, no rebuild needed!

Next Steps

• Try Example 05: Graph import (MovieLens as vertices and edges)
• Experiment: Modify commit_every values to see performance impact
• Add queries: Try your own analysis queries on the dataset
• Index tuning: Create different index combinations and measure speedup
• Type testing: Change type inference rules and observe import behavior

Related Examples

• Example 01 - Simple Document Store - Document basics and CRUD
• Example 02 - Social Network Graph - Graph modeling with NULL handling
• Example 03 - Vector Search - Semantic similarity search

---

Dataset License: MovieLens data is provided by GroupLens Research and is free to use for educational purposes. See https://grouplens.org/datasets/movielens/ for details.