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En Croissant uses SQLite databases to efficiently store and query large collections of chess games. This guide covers everything you need to know about database management.

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Creating Databases

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From Local PGN Files

1

Open the Database Page

Navigate to the Databases section from the sidebar.
2

Click Add Database

Click the “Add Database” button (+ icon) to open the creation dialog.
3

Select Local Tab

In the modal, switch to the “Local” tab.
4

Choose Your PGN File

  • Click to select a PGN file from your computer
  • Supported formats: .pgn and .pgn.zst (compressed)
  • The database name will auto-populate from the filename
5

Configure Database

  • Name: Edit the auto-generated name if desired (required)
  • Description: Add an optional description for organization
6

Convert and Import

Click “Convert” to begin the import process. Large databases may take several minutes.
During conversion, you’ll see progress statistics including total games imported and conversion speed (games/second).

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From Online Sources

En Croissant provides curated databases that can be downloaded directly:
1

Open Add Database Dialog

Click the “Add Database” button on the Databases page.
2

Browse Web Databases

Stay on the “Web” tab to see available databases.
3

Choose a Database

Each database card shows:
  • Size: Download size
  • Games: Number of games included
  • Players: Number of unique players
4

Install

Click “Install” to download and set up the database automatically.

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Database Settings

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General Settings

Select any database to view and edit its settings:
  • Name: The display name (must be unique)
  • Description: Optional notes about the database contents
  • Reference Database: Mark with a star to use for opening references

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Indexing

Indexing creates additional data structures that dramatically speed up searches and queries. Indexed databases are much faster for filtering games by player, date, or result.Trade-offs:
  • Pros: 10-100x faster queries, required for large databases
  • Cons: Increases storage size by ~20-30%
1

Select Database

Click on a database to view its settings panel.
2

Enable Indexing

Check the “Indexed” checkbox. The indexing process will begin automatically.
3

Wait for Completion

A loading indicator shows progress. Large databases may take several minutes to index.
Always enable indexing for databases with more than 10,000 games to ensure optimal performance.

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Adding Games to Existing Databases

You can append additional games to any database:
1

Select the Database

Click on the database you want to add games to.
2

Click Add Games

In the settings panel, click the “Add Games” button (+ icon).
3

Select PGN File

Choose a PGN file containing the games to import.
4

Automatic Merge

Games will be appended to the database. The game count updates automatically.

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Database Formats and Conversions

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Supported Formats

Import formats:
  • .pgn - Standard Portable Game Notation
  • .pgn.zst - Zstandard compressed PGN (recommended for large files)
Database format:
  • .db3 - SQLite 3 database (En Croissant’s native format)

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Exporting to PGN

Export any database back to PGN format:
1

Select Database

Click the database you want to export.
2

Click Export PGN

In the settings panel, click “Export PGN” (→ icon).
3

Choose Save Location

Select where to save the .pgn file.
4

Wait for Export

Large databases may take time to export.

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Maintenance and Optimization

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Removing Duplicate Games

Over time, databases may accumulate duplicate games from multiple imports:
1

Navigate to Advanced Tools

Select your database and scroll to the “Advanced Tools” section.
2

Click Remove Duplicates

Click “Remove Duplicates” under Batch Delete operations.
3

Confirm and Wait

The operation scans for games with identical moves and metadata, keeping only one copy of each.

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Removing Empty Games

Some PGN files contain game headers without moves. Remove these:
1

Access Advanced Tools

Select the database and find the “Advanced Tools” section.
2

Click Remove Empty

Click “Remove Empty” to delete all games with zero moves.

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Merging Players

Player names may have variations (e.g., “Carlsen, M” vs “Carlsen, Magnus”). Merge them:
1

Find Merge Players Tool

In Advanced Tools, locate the “Merge Players” section.
2

Search for Player 1

Use the search box to find the first player name.
3

Search for Player 2

Search for the second player name (the duplicate).
4

Merge

Click the merge button (→) to combine all games under the first player’s name.
Player merging is permanent. All games attributed to Player 2 will be reassigned to Player 1.

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Backup Strategies

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Manual Backups

  1. Locate Database Folder: Click the folder icon next to “Databases” to open the storage directory
  2. Copy .db3 Files: Copy your database files to a backup location
  3. Schedule Regular Backups: Especially important for custom databases with annotations

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Export as PGN

For long-term archival:
  • Export databases to PGN format (universal standard)
  • PGN files can be reimported or opened in any chess software
  • Consider compressing with .zst for storage efficiency

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Exploring Database Content

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Opening a Database

Double-click any database card to open the database explorer with three views:
  1. Games View: Browse and filter all games
  2. Players View: See player statistics and their games
  3. Tournaments View: Explore events and competitions

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Reference Databases

Mark a database as “Reference” (star icon) to:
  • Display opening statistics in analysis
  • Show game continuations from master games
  • View win/draw/loss percentages for positions
Use a large, high-quality database (like the Lichess database) as your reference for best results.

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Troubleshooting

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Database Won’t Load

If a database shows an error:
  • Check the error message: Hover over or select the database to see details
  • File corruption: Try re-importing from the original PGN
  • Format issues: Ensure the PGN file is valid

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Slow Performance

  • Enable indexing: Essential for databases over 10,000 games
  • Remove duplicates: Reduces database size and improves speed
  • Check disk space: Ensure adequate space for indexing operations

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Import Errors

  • Verify PGN format: Open the file in a text editor to check for corruption
  • Try smaller batches: Split very large PGN files into smaller chunks
  • Check file encoding: Ensure UTF-8 encoding

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Best Practices

Name Consistently

Use clear, descriptive names that indicate the database content (e.g., “Lichess Elite 2023” rather than “db1”).

Index Large Databases

Always enable indexing for databases with 10,000+ games to maintain fast query performance.

Regular Maintenance

Periodically remove duplicates and empty games to keep databases clean and efficient.

One Reference Database

Mark only your most comprehensive database as the reference to avoid conflicting statistics.

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