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En Croissant provides powerful search capabilities for exploring chess databases. Search by position, filter games by player or tournament, and analyze opening statistics across millions of games. Position search finds all games that contain a specific chess position. This is one of En Croissant’s most powerful features, using memory-mapped binary indexes for instant results.

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Search types

Matches the exact position including:
  • Piece placement on all squares
  • Side to move
  • Castling rights
  • En passant square
Use case: Find games that reached an exact position from your current game.

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How position search works

1

Set up the position

Navigate to the position you want to search for on the analysis board.
2

Open database search

Click the “Search Database” button. Select the database you want to search.
3

Choose search type

Select “Exact” for precise position matching or “Partial” for pattern matching.
4

View results

Results show:
  • Move statistics (most played moves from this position)
  • Win/draw/loss percentages for each move
  • Sample games from high-rated players

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Position search optimization

En Croissant uses several optimizations for fast position search: Material-based filtering: 
// Quick pre-check before examining moves
// From src-tauri/src/db/search.rs
fn is_material_reachable(end: &MaterialCount, pos: &MaterialCount) -> bool {
    end.white <= pos.white && end.black <= pos.black
}
Pawn structure indexing:
  • Tracks pawns on 2nd and 7th ranks as 16-bit integer
  • Enables instant filtering for exact position search
  • Reduces search space by 90%+ for endgame positions
Parallel search:
  • Uses all CPU cores via Rayon parallel iterators
  • Processes millions of games in seconds
  • Lock-free aggregation of results
Position search on a database with 2 million games typically completes in 2-5 seconds, examining every game’s move sequence.

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Move statistics

For each position found, En Croissant displays: 
interface PositionStats {
  move: string;        // Move in SAN notation (e.g., "Nf3")
  white: number;       // Games where White won after this move  
  draw: number;        // Games that ended in a draw
  black: number;       // Games where Black won after this move
}
Moves are sorted by popularity, helping you identify the most common and successful continuations.

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Sample games

The search returns up to 10 sample games from the highest-rated players:
  • Games are ranked by maximum player rating (White or Black)
  • Only the top 10 rated games are returned
  • Includes full game notation and headers
  • Click any game to load it in the analysis board
This is implemented using a min-heap to efficiently track top games while processing millions of candidates. Filter and search games in the database using multiple criteria:
1

Open the Players tab

In database view, switch to the Players tab to see all players in the database.
2

Search by name

Use the search box to find players by name (supports partial matching).
-- Search uses SQL LIKE with wildcards
WHERE players.name LIKE '%Carlsen%'
3

Filter by rating

Set minimum and maximum ELO ratings to find players in a specific range.
4

View player games

Click any player to see all their games in the database, along with statistics.

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Game filters

Combine multiple filters to find specific games:

Player filters

  • Player 1 (White or Black)
  • Player 2 (Opponent)
  • Side selection (White/Black/Any)
  • ELO rating ranges for each player

Game metadata

  • Tournament/Event name
  • Date range (from/to)
  • Game result (1-0, 0-1, 1/2-1/2)
  • Time control

Position-based

  • Position search (exact or partial)
  • Desired result from position
  • Material count filters
  • Ply count (game length)

Sorting options

  • Date (newest/oldest first)
  • Rating (highest/lowest)
  • Game length (ply count)
  • Game ID

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Advanced filtering example

Find all games where:
  • Magnus Carlsen played with White pieces
  • Against opponents rated 2700+
  • Reached the Ruy Lopez opening (e4 e5 Nf3 Nc6 Bb5)
  • Resulted in a White win
const query: GameQuery = {
  player1: carlsenId,
  sides: "WhiteBlack",
  range2: [2700, 3000],
  position: {
    fen: "r1bqkbnr/pppp1ppp/2n5/1B2p3/4P3/5N2/PPPP1PPP/RNBQK2R",
    type: "exact"
  },
  outcome: "1-0",
  options: {
    sort: "date",
    direction: "desc",
    page: 1,
    pageSize: 50
  }
};
Explore games by tournament:

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Finding tournaments

1

Navigate to Tournaments tab

Switch to the Tournaments tab in database view to see all events.
2

Search by name

Find specific tournaments using the search box (e.g., “World Championship”, “Tata Steel”).
3

View tournament games

Click a tournament to filter games to only that event.

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Tournament statistics

For each tournament, view:
  • Total games played
  • Date range of games
  • Players who participated
  • Average rating of participants

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Search performance

En Croissant’s search system is optimized for speed:

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Memory-mapped indexing

// From src-tauri/src/db/search_index.rs
pub struct MmapSearchIndex {
    // Memory-mapped file for instant access
    // No loading time, even for multi-GB indexes
    mmap: Arc<Mmap>,
    entry_count: usize,
}
Benefits:
  • Instant “loading” of multi-GB search indexes
  • Zero memory overhead (uses OS page cache)
  • Shared across multiple searches

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Parallel processing

// Search uses all CPU cores
mmap_index.par_iter().for_each(|entry| {
    // Process game entry
    if matches_query(entry) {
        // Aggregate results lock-free with DashMap
    }
});

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Search result caching

Recent searches are cached in memory:
  • Cache key: (GameQuery, database_path)
  • Prevents redundant searches of the same position
  • Automatically cleared when database is modified
  • Collision detection prevents concurrent duplicate searches
The first search on a database generates the search index file (.idx). This can take 1-5 minutes for large databases but only happens once.

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Search patterns and tips

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Opening preparation

  1. Navigate to your opening position
  2. Search database for exact position
  3. Review most popular moves and their win rates
  4. Load sample games from strong players
  5. Identify critical variations to study

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Endgame study

  1. Set up the endgame position (e.g., R+P vs R)
  2. Use partial position search to find all games with that material
  3. Study how strong players converted or held the position
  4. Filter by player rating for high-quality examples

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Player preparation

  1. Search for your opponent’s name in Players tab
  2. Filter their games by color and opening
  3. Identify their most common lines
  4. Search specific positions from their games
  5. Find their weaknesses or unfamiliar variations

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Pattern recognition

  1. Set up a tactical pattern (e.g., knight fork setup)
  2. Use partial search to find all games with that pattern
  3. Study the context in which the pattern arose
  4. Build pattern recognition skills

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Combining position search with analysis

Integrate database search into your analysis workflow:
1

Analyze your game

Load a game into the analysis board and navigate to an interesting position.
2

Search database

Click “Search Database” to see how others played this position.
3

Compare with engine

Use engine analysis alongside database statistics to find the objectively best move vs. the most popular move.
4

Study deviations

When the database shows a different move than the engine, load sample games to understand the practical considerations.

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Search API

The search system is exposed through Tauri commands: 
#[tauri::command]
pub async fn search_position(
    file: PathBuf,           // Database file path
    query: GameQuery,        // Search criteria
    app: AppHandle,          // For progress updates
    tab_id: String,          // For tracking search progress
    state: State<AppState>,  // App state with caches
) -> Result<(Vec<PositionStats>, Vec<NormalizedGame>), Error>
Progress updates are emitted during long searches: 
// Listen for search progress
events.on('search_progress', (payload) => {
  console.log(`Search ${payload.progress}% complete`);
});
Search progress is updated every 50,000 games processed to avoid UI overhead.

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