Database operations

DB plugin provides two layers for interacting with your data: the Query API for building and executing queries, and the Database interface for lower-level operations like index management, batch reads, and utilities. For most use cases, prefer the Query API.

Practical examples

Search with filters

1Query<Article> q = Query.from(Article.class);
2
3// Full-text search
4if (query != null && !query.isEmpty()) {
5    q.where("_any matches ?", query);
6}
7
8// Filter by author
9if (author != null) {
10    q.and("author = ?", author);
11}
12
13// Date range
14if (startDate != null) {
15    q.and("publishDate >= ?", startDate);
16}
17if (endDate != null) {
18    q.and("publishDate <= ?", endDate);
19}
20
21// Pagination
22int offset = (page - 1) * pageSize;
23return q.sortDescending("publishDate")
24    .select(offset, pageSize);

Dynamic query building

1Query<Article> query = Query.from(Article.class);
2
3for (Map.Entry<String, Object> entry : filters.entrySet()) {
4    String field = entry.getKey();
5    Object value = entry.getValue();
6
7    query.and(field + " = ?", value);
8}
9
10List<Article> results = query.selectAll();

1// Find articles with overlapping tags, same author, or similar title
2PaginatedResult<Article> related = Query.from(Article.class)
3    .where("_id != ?", article.getId())  // Exclude current article
4    .and("tags = ?", article.getTags())  // Matching tags
5    .or("author = ?", article.getAuthor())  // Same author
6    .sortDescending("publishDate")
7    .select(0, limit);

Faceted search

1Query<Article> baseQuery = Query.from(Article.class)
2    .where("_any matches ?", searchQuery);
3
4// Get articles
5PaginatedResult<Article> articles = baseQuery
6    .sortRelevant(100, "_any matches ?", searchQuery)
7    .select(0, 20);
8
9// Get author facets
10Map<String, Long> authorCounts = new HashMap<>();
11List<Grouping<Article>> authorGroups = baseQuery
12    .groupBy("author");
13for (Grouping<Article> group : authorGroups) {
14    Author author = (Author) group.getKeys().get(0);
15    authorCounts.put(author.getName(), group.getCount());
16}
17
18// Get tag facets
19Map<String, Long> tagCounts = new HashMap<>();
20List<Grouping<Article>> tagGroups = baseQuery
21    .groupBy("tags");
22for (Grouping<Article> group : tagGroups) {
23    String tag = (String) group.getKeys().get(0);
24    tagCounts.put(tag, group.getCount());
25}

Soft delete pattern

1public class SoftDeleteArticle extends Record {
2
3    private String title;
4
5    @Indexed(visibility = true)
6    private Date deletedDate;
7
8    public boolean isDeleted() {
9        return deletedDate != null;
10    }
11
12    public void softDelete() {
13        this.deletedDate = new Date(Database.Static.getDefault().now());
14        this.save();
15    }
16
17    public void restore() {
18        this.deletedDate = null;
19        this.save();
20    }
21
22    public String getTitle() {
23        return title;
24    }
25
26    public void setTitle(String title) {
27        this.title = title;
28    }
29
30    public Date getDeletedDate() {
31        return deletedDate;
32    }
33
34    public void setDeletedDate(Date deletedDate) {
35        this.deletedDate = deletedDate;
36    }
37}

When querying, records with populated visibility-indexed fields are automatically hidden:

1// Query hides articles with populated visibility indexes
2List<SoftDeleteArticle> activeArticles = Query.from(SoftDeleteArticle.class)
3    .selectAll();

Cascading delete

1public class CascadingDeleteAuthor extends Record {
2
3    private String name;
4
5    @Override
6    protected void beforeDelete() {
7        Database db = Database.Static.getDefault();
8
9        // Delete all articles by this author
10        db.deleteByQuery(
11            Query.from(Article.class)
12                .where("author = ?", this)
13        );
14    }
15
16    public String getName() {
17        return name;
18    }
19
20    public void setName(String name) {
21        this.name = name;
22    }
23}

Cache invalidation with notifiers

1public class CacheInvalidatorExample {
2
3    private final Cache<UUID, Article> cache;
4
5    public CacheInvalidatorExample(Database db, Cache<UUID, Article> cache) {
6        this.cache = cache;
7
8        // Invalidate cache on updates
9        db.addUpdateNotifier(new UpdateNotifier<Article>() {
10
11            @Override
12            public void onUpdate(Article article) {
13                cache.remove(article.getId());
14            }
15        });
16
17        // Invalidate cache on deletes
18        db.addDeleteNotifier(new DeleteNotifier<Article>() {
19
20            @Override
21            public void onDelete(Article article) {
22                cache.remove(article.getId());
23            }
24        });
25    }
26
27    public Article get(UUID id) {
28        return cache.get(
29            id, key -> {
30                return Database.Static.getDefault().readFirst(
31                    Query.from(Article.class).where("_id = ?", key)
32                );
33            });
34    }
35
36    // Simple cache interface for example purposes
37    public interface Cache<K, V> {
38
39        V get(K key, java.util.function.Function<K, V> loader);
40
41        void remove(K key);
42    }
43}

Query API

The Query class provides a fluent API for building and executing database queries. Inspired by Apple's Cocoa Predicates and LINQ, it offers a clean, readable syntax for expressing complex query logic.

Query construction

1// Query a specific type
2Query<Article> query = Query.from(Article.class);
3
4// Query all types
5Query<Object> allQuery = Query.fromAll();
6
7// Query by ObjectType
8ObjectType articleType = ObjectType.getInstance(Article.class);
9Query<Object> typeQuery = Query.fromType(articleType);
10
11// Query by type group (multiple related types)
12Query<Object> contentQuery = Query.fromGroup("content");

To query against a specific database:

1Database searchDb = Database.Static.getInstance("search");
2
3Query<Article> query = Query.from(Article.class)
4    .using(searchDb);

Predicates and filtering

where - initial predicate

Set the initial query predicate:

1// Simple equality
2Query.from(Article.class)
3    .where("title = ?", "Getting Started");
4
5// Comparison
6Query.from(Article.class)
7    .where("publishDate > ?", cutoffDate);
8
9// Multiple parameters
10Query.from(Article.class)
11    .where("title = ? and author = ?", "Getting Started", author);

and - add AND conditions

Chain additional conditions with AND:

1Query.from(Article.class)
2    .where("publishDate > ?", cutoffDate)
3    .and("author/name = ?", "John Doe")
4    .and("tags = ?", "java");

or - add OR conditions

Chain conditions with OR:

1Query.from(Article.class)
2    .where("author/name = ?", "John Doe")
3    .or("author/name = ?", "Jane Smith");
4
5// Complex combinations
6// (publishDate > cutoff) OR (featured = true AND author = john)
7Query.from(Article.class)
8    .where("publishDate > ?", cutoffDate)
9    .or("featured = ? and author = ?", true, john);

not - negate conditions

1// Articles NOT by John Doe
2Query.from(Article.class)
3    .where("author/name != ?", "John Doe");
4
5// Or using not()
6Query.from(Article.class)
7    .not("author/name = ?", "John Doe");

having - filter without affecting ranking

Use having to apply predicates that filter results without affecting ranking in full-text search databases (like Solr). Unlike and or or, which can influence the relevance score, having applies the predicate purely as a filter:

1// Search with full-text ranking, but filter by category without affecting relevance scores
2// Unlike and() or or(), having() applies the predicate purely as a filter
3Query.from(Article.class)
4    .where("_any matches ?", "database performance")  // Affects ranking
5    .having("category = ?", "technology");            // Filters only, no ranking impact

Predicate operators

Equality operators

1// Equals
2Query.from(Article.class)
3    .where("status = ?", "published");
4
5// Not equals
6Query.from(Article.class)
7    .where("status != ?", "draft");
8
9// Null/missing check
10Query.from(Article.class)
11    .where("deletedDate = missing");
12
13Query.from(Article.class)
14    .where("deletedDate != missing");

Comparison operators

1// Greater than
2Query.from(Article.class)
3    .where("publishDate > ?", date);
4
5// Greater than or equal
6Query.from(Article.class)
7    .where("publishDate >= ?", date);
8
9// Less than
10Query.from(Article.class)
11    .where("publishDate < ?", date);
12
13// Less than or equal
14Query.from(Article.class)
15    .where("publishDate <= ?", date);

String operators

1// Starts with
2Query.from(Article.class)
3    .where("title ^= ?", "Getting");
4
5// Contains
6Query.from(Article.class)
7    .where("content contains ?", "database");

Collection operators

1// Contains any of the values
2Query.from(Article.class)
3    .where("tags = ?", Arrays.asList("java", "database"));
4
5// Contains all values
6Query.from(Article.class)
7    .where("tags = ?", tag1)
8    .and("tags = ?", tag2);  // Both tags must be present

Range queries

1// Between dates
2Query.from(Article.class)
3    .where("publishDate > ? and publishDate < ?", startDate, endDate);

Full-text search

1// Search across all indexed fields
2Query.from(Article.class)
3    .where("_any matches ?", "search terms");
4
5// Search specific field
6Query.from(Article.class)
7    .where("content matches ?", "search terms");

Special field keys

1// _id - Object ID
2Query.from(Article.class)
3    .where("_id = ?", articleId);
4
5// Multiple IDs
6Query.from(Article.class)
7    .where("_id = ?", Arrays.asList(id1, id2, id3));
8
9// _type - Object Type
10Query.from(Article.class)
11    .where("_type = ?", Article.class);
12
13// _any - Search All Fields
14Query.from(Article.class)
15    .where("_any matches ?", "search query");
16
17// _label - Display Label
18Query.from(Article.class)
19    .where("_label matches ?", "Article");

Path-based field access

Query nested fields using path notation:

1// Author's name
2Query.from(Article.class)
3    .where("author/name = ?", "John Doe");
4
5// Nested objects
6Query.from(Article.class)
7    .where("author/company/name = ?", "Acme Corp");
8
9// Collection items
10Query.from(Article.class)
11    .where("comments/author/name = ?", "Jane Smith");
12
13// Map values
14Query.from(Article.class)
15    .where("metadata/category = ?", "technology");

Sorting

sortAscending

1Query.from(Article.class)
2    .sortAscending("title");
3
4// Multiple fields
5Query.from(Article.class)
6    .sortAscending("author/name")
7    .sortAscending("publishDate");

sortDescending

1Query.from(Article.class)
2    .sortDescending("publishDate");

Sort by relevance

Sort by relevance to a predicate (requires search-capable database):

1Query.from(Article.class)
2    .where("_any matches ?", "java database")
3    .sortRelevant(100, "_any matches ?", "java database");

Sort by newest/oldest

1// Newest first
2Query.from(Article.class)
3    .sortNewest(100, "publishDate");
4
5// Oldest first
6Query.from(Article.class)
7    .sortOldest(100, "publishDate");

Multiple sort criteria

1Query.from(Article.class)
2    .sortDescending("featured")      // Featured articles first
3    .sortDescending("publishDate")   // Then by date
4    .sortAscending("title");         // Then by title

Query execution

selectAll

Execute query and return all results:

1List<Article> articles = Query.from(Article.class)
2    .where("publishDate > ?", cutoffDate)
3    .selectAll();

select (pagination)

Execute with offset and limit:

1// First page (items 0-9)
2PaginatedResult<Article> page1 = Query.from(Article.class)
3    .sortDescending("publishDate")
4    .select(0, 10);
5
6// Second page (items 10-19)
7PaginatedResult<Article> page2 = Query.from(Article.class)
8    .sortDescending("publishDate")
9    .select(10, 10);
10
11// Calculate offset from page number
12int page = 3;
13int pageSize = 10;
14int offset = (page - 1) * pageSize;
15Query<Article> query = Query.from(Article.class);
16PaginatedResult<Article> pageN = query.select(offset, pageSize);

first

Get the first result (or null):

1Article article = Query.from(Article.class)
2    .where("slug = ?", "getting-started")
3    .first();
4
5if (article == null) {
6    // Not found
7}

findFirst (Optional)

Get the first result as an Optional:

1Optional<Article> optional = Query.from(Article.class)
2    .where("slug = ?", "getting-started")
3    .findFirst();
4
5optional.ifPresent(article -> {
6    System.out.println("Found: " + article.getTitle());
7});
8
9// Or with default
10Article article = Query.from(Article.class)
11    .where("slug = ?", "getting-started")
12    .findFirst()
13    .orElse(defaultArticle);

count

Count matching objects:

1long total = Query.from(Article.class).count();
2
3long published = Query.from(Article.class)
4    .where("publishDate != missing")
5    .count();

iterable

Get a streaming iterable for large result sets:

1Query<Article> query = Query.from(Article.class)
2    .where("publishDate > ?", cutoffDate);
3
4for (Article article : query.iterable(100)) {  // Fetch size 100
5    // Process each article
6    // Memory efficient for large datasets
7}

deleteAll

Delete all matching objects:

1// Delete old draft articles
2Query.from(Article.class)
3    .where("status = ? and createdDate < ?", "draft", cutoffDate)
4    .deleteAll();

Grouping and aggregation

groupBy

Group results by one or more fields:

1// Group by author
2List<Grouping<Article>> byAuthor = Query.from(Article.class)
3    .groupBy("author");  // Returns List<Grouping<Article>>
4
5for (Grouping<Article> group : byAuthor) {
6    Author author = (Author) group.getKeys().get(0);
7    long count = group.getCount();
8    System.out.println(author.getName() + ": " + count + " articles");
9}

1// Group by multiple fields
2List<Grouping<Article>> groups = Query.from(Article.class)
3    .groupBy("author", "publishYear");
4
5for (Grouping<Article> group : groups) {
6    Author author = (Author) group.getKeys().get(0);
7    Integer year = (Integer) group.getKeys().get(1);
8    long count = group.getCount();
9    System.out.println(author.getName() + " in " + year + ": " + count);
10}

Filtering grouped results

1// Authors with more than 5 articles
2List<Grouping<Article>> prolificAuthors = Query.from(Article.class)
3    .groupBy("author")
4    .stream()
5    .filter(group -> group.getCount() > 5)
6    .collect(Collectors.toList());

Aggregation functions

1// Get count for each group
2for (Grouping<Article> group : groups) {
3    long count = group.getCount();
4    // Use count...
5}
6
7// Access first item in group
8for (Grouping<Article> group : groups) {
9    Article firstArticle = group.createItemsQuery().first();
10    // Use firstArticle...
11}
12
13// Get all items in group
14for (Grouping<Article> group : groups) {
15    List<Article> articles = group.createItemsQuery().selectAll();
16    // Process all articles in this group...
17}

Query modifiers

timeout

Set query timeout in seconds:

1Query.from(Article.class)
2    .timeout(30.0)  // 30 second timeout
3    .selectAll();

noCache

Bypass query result cache:

1Query.from(Article.class)
2    .noCache()
3    .selectAll();

master

Execute on master/primary database (force read from write source):

1// Ensure we read from master, not replica
2Query.from(Article.class)
3    .master()
4    .where("_id = ?", articleId)
5    .first();

Useful when:

You just wrote data and need to read it immediately
Avoiding replication lag
Critical reads that must be up-to-date

resolveToReferenceOnly

Load only reference information, not full objects:

1List<Article> refs = Query.from(Article.class)
2    .resolveToReferenceOnly()
3    .selectAll();
4
5// refs contains lightweight reference objects
6// Good for getting IDs, types, but not full data

resolveInvisible

Include records marked as invisible:

1Query.from(Article.class)
2    .resolveInvisible()
3    .selectAll();

option

Set database-specific options:

1Query.from(Article.class)
2    .option("hint", "USE INDEX (idx_author)")  // SQL hint
3    .option("readPreference", "secondary")     // MongoDB option
4    .selectAll();

comment

Add an informational comment to the query:

1Query.from(Article.class)
2    .comment("Dashboard recent articles widget")
3    .selectAll();

Useful for:

Debugging slow queries
Monitoring and logging
Tracking query origins in database logs

Subqueries

Use queries as predicate values for powerful filtering:

1// Find articles by authors in California
2List<Article> articles = Query.from(Article.class)
3    .where(
4        "author = ?",
5        Query.from(Author.class)
6            .where("state = ?", "CA")
7    )
8    .selectAll();
9
10// Find articles NOT by specific authors
11List<Article> filtered = Query.from(Article.class)
12    .where(
13        "author != ?",
14        Query.from(Author.class)
15            .where("blacklisted = ?", true)
16    )
17    .selectAll();

1// Complex subquery
2Query<Article> articles = Query.from(Article.class)
3    .where(
4        "author = ?",
5        Query.from(Author.class)
6            .where(
7                "company = ?",
8                Query.from(Company.class)
9                    .where("name = ?", "Acme Corp")
10            )
11    );

Write operations

save

Saves an object with full validation:

1Article article = new Article();
2article.setTitle("New Article");
3article.setAuthor(author);
4article.setPublishDate(new Date());
5
6try {
7    db.save(article.getState());
8    // or simply: article.save();
9} catch (ValidationException e) {
10    // Handle validation errors
11    for (ObjectField field : e.getStates()
12        .stream()
13        .map(State::getErrorFields)
14        .flatMap(Collection::stream)
15        .collect(Collectors.toList())) {
16        System.out.println("Error in " + field.getInternalName() + ": "
17            + field.getState().getFieldErrors(field));
18    }
19}

The save process:

Validates all fields (annotations + custom validation)
Fires beforeSave() hooks
Writes to database
Updates indexes
Fires afterSave() hooks

saveUnsafely

Saves without validation (use with caution):

1// Skip validation for performance-critical paths
2db.saveUnsafely(article.getState());

When to use:

Importing trusted data
System-level operations
Performance-critical batch operations where you've pre-validated

When NOT to use:

User input
External data sources
When data integrity is critical

delete

Deletes an object:

1db.delete(article.getState());
2// or: article.delete();

The delete process:

Fires beforeDelete() hooks
Removes from database
Updates indexes
Fires afterDelete() hooks

deleteByQuery

Deletes all objects matching a query:

1// Delete old articles
2Date cutoff = DateUtils.addMonths(new Date(), -12);
3db.deleteByQuery(
4    Query.from(Article.class)
5        .where("publishDate < ?", cutoff)
6);

warning

This bypasses lifecycle hooks for performance. If you need hooks to fire, load and delete objects individually:

1List<Article> articles = Query.from(Article.class)
2    .where("publishDate < ?", cutoff)
3    .selectAll();
4
5db.beginWrites();
6try {
7    for (Article article : articles) {
8        article.delete();  // Fires hooks
9    }
10    db.commitWrites();
11} finally {
12    db.endWrites();
13}

Database interface

The Database interface provides lower-level methods for operations not covered by the Query API. For read operations, prefer Query unless you need direct database access.

Getting a database instance

Default database

1Database db = Database.Static.getDefault();

Named database

1Database searchDb = Database.Static.getInstance("search");

All databases

1List<Database> allDatabases = Database.Static.getAll();

By type

1List<SqlDatabase> sqlDatabases = Database.Static.getByClass(SqlDatabase.class);

Temporary override

Temporarily override the default database for the current thread:

1Database specialDb = Database.Static.getInstance("special");
2
3Database.Static.overrideDefault(specialDb);
4try {
5    // All operations in this block use specialDb
6    article.save();
7    Query.from(Article.class).selectAll();
8} finally {
9    Database.Static.restoreDefault();
10}

Read methods

note

For most read operations, use the Query API instead. The Database read methods are useful when you need to work with raw Query objects or implement custom database logic.

readAll

Reads all objects matching a query:

1Query<Article> query = Query.from(Article.class)
2    .where("publishDate > ?", cutoffDate);
3
4List<Article> articles = db.readAll(query);

readFirst

Reads the first object matching a query:

1Article article = db.readFirst(
2    Query.from(Article.class)
3        .where("title = ?", "Getting Started")
4);
5
6if (article == null) {
7    // No matching article found
8}

readCount

Returns the count of objects matching a query:

1long totalArticles = db.readCount(
2    Query.from(Article.class)
3);
4
5long publishedCount = db.readCount(
6    Query.from(Article.class)
7        .where("publishDate != missing")
8);

readPartial

Reads a subset of results with offset and limit (pagination):

1// Page 1: items 0-9
2PaginatedResult<Article> page1 = db.readPartial(
3    Query.from(Article.class).sortDescending("publishDate"),
4    0,    // offset
5    10    // limit
6);
7
8// Page 2: items 10-19
9PaginatedResult<Article> page2 = db.readPartial(
10    Query.from(Article.class).sortDescending("publishDate"),
11    10,   // offset
12    10    // limit
13);

readIterable

Returns an iterable for streaming large result sets without loading everything into memory:

1Query<Article> query = Query.from(Article.class);
2Iterable<Article> articles = db.readIterable(query, 100); // Fetch size
3
4for (Article article : articles) {
5    // Process each article
6    System.out.println(article.getTitle());
7
8    // Memory is managed efficiently - old items can be garbage collected
9}

This is useful for:

Processing large datasets
Export operations
Batch processing
Reducing memory footprint

readAllGrouped

Reads grouped results with aggregations:

1// Group articles by author
2List<Grouping<Article>> groupings = db.readAllGrouped(
3    Query.from(Article.class),
4    "author"
5);
6
7for (Grouping<Article> grouping : groupings) {
8    Author author = (Author) grouping.getKeys().get(0);
9    long count = grouping.getCount();
10    System.out.println(author.getName() + ": " + count + " articles");
11}

1// Group by multiple fields
2List<Grouping<Article>> groupings = db.readAllGrouped(
3    Query.from(Article.class),
4    "author",
5    "publishDate.year"  // Group by year
6);
7
8for (Grouping<Article> grouping : groupings) {
9    Author author = (Author) grouping.getKeys().get(0);
10    Integer year = (Integer) grouping.getKeys().get(1);
11    long count = grouping.getCount();
12    System.out.println(author.getName() + " in " + year + ": " + count);
13}

readPartialGrouped

Paginated version of readAllGrouped:

1PaginatedResult<Grouping<Article>> page = db.readPartialGrouped(
2    Query.from(Article.class),
3    0,     // offset
4    10,    // limit
5    "author"
6);

readLastUpdate

Returns the most recent update time for objects matching a query:

1Date lastUpdate = db.readLastUpdate(
2    Query.from(Article.class)
3);
4
5if (lastUpdate != null) {
6    System.out.println("Last article update: " + lastUpdate);
7}

Useful for:

Cache invalidation
Change detection
Synchronization checks

Index operations

index

Updates indexes for a specific object:

1// Re-index after making changes that affect queries
2article.setTitle("Updated Title");
3db.index(article.getState());

Typically you don't need to call this directly as save() handles indexing. Use it when:

Manually updating index data
Recovering from index corruption
Implementing custom indexing strategies

indexAll

Re-indexes all objects for a specific index:

1ObjectType articleType = ObjectType.getInstance(Article.class);
2ObjectIndex titleIndex = articleType.getIndex("title");
3
4// Re-index all articles for the title index
5db.indexAll(titleIndex);

Use cases:

Adding a new index to existing data
Recovering from index corruption
Changing index definitions

recalculate

Recalculates specific indexes for an object:

1ObjectType type = ObjectType.getInstance(Article.class);
2ObjectIndex authorIndex = type.getIndex("author");
3ObjectIndex dateIndex = type.getIndex("publishDate");
4
5// Recalculate only these indexes
6db.recalculate(article.getState(), authorIndex, dateIndex);

More efficient than full re-indexing when you know exactly which indexes need updates.

Batch operations

Batch reads

Read multiple objects by ID efficiently:

1List<UUID> articleIds = Arrays.asList(id1, id2, id3, id4, id5);
2
3List<Article> articles = Query.from(Article.class)
4    .where("_id = ?", articleIds)
5    .selectAll();

Batch writes

Write multiple objects in a single transaction:

1db.beginWrites();
2try {
3    for (Article article : articles) {
4        db.save(article.getState());
5    }
6    db.commitWrites();  // All saved atomically
7} finally {
8    db.endWrites();
9}

Benefits:

Atomic (all succeed or all fail)
Better performance
Validation happens before any writes
Single database roundtrip

Database utilities

ping

Check if the database is available:

1// Ping replica/read connection
2try {
3    db.ping(false);
4
5    // Ping primary/write connection
6    db.ping(true);
7} catch (Exception e) {
8    System.out.println("Ping failed: " + e.getMessage());
9    throw new RuntimeException(e);
10}

Use in:

Health checks
Monitoring
Graceful degradation logic

now

Get the database server's current time:

1long dbTime = db.now();
2
3// Example: Set timestamp from database
4article.setPublishDate(new Date(db.now()));
5article.save();

Why use this instead of new Date()?

Consistent timestamps across distributed systems
Avoids clock skew between app servers
Some databases have special time functions

getName / setName

1String name = db.getName();
2db.setName("newName");

Database names are used to:

Identify databases in multi-database configurations
Route queries to specific databases
Configure database-specific settings

Environment (deprecated)

note

getEnvironment() and setEnvironment() are deprecated. Use DatabaseEnvironment.getCurrent() and DatabaseEnvironment.override() instead.

Notifiers (update listeners)

Update notifiers

1// Listen for article updates
2db.addUpdateNotifier(new UpdateNotifier<Article>() {
3
4    @Override
5    public void onUpdate(Article article) {
6        cacheService.invalidate(article.getId());
7    }
8});

Delete notifiers

1// Listen for article deletions
2db.addDeleteNotifier(new DeleteNotifier<Article>() {
3
4    @Override
5    public void onDelete(Article article) {
6        // Handle deletion
7        cacheService.remove(article.getId());
8        searchIndex.remove(article.getId());
9    }
10});

Removing notifiers

1UpdateNotifier<Article> notifier = new UpdateNotifier<Article>() {
2
3    @Override
4    public void onUpdate(Article article) {
5        // Handle updates
6    }
7};
8db.addUpdateNotifier(notifier);
9
10// Later, remove it
11db.removeUpdateNotifier(notifier);

Check notifier support

1if (db.canCallNotifiers()) {
2    // This database supports notifiers
3    db.addUpdateNotifier(notifier);
4} else {
5    // Use polling or other mechanisms
6}

note

Not all database implementations support notifiers. AbstractSqlDatabase typically does, but some specialized databases may not.

Performance tips

Index your query fields

1// Ensure queried fields are indexed
2// @Indexed
3// private String title;
4//
5// @Indexed
6// private Date publishDate;
7//
8// @Indexed
9// private Author author;

Use batch operations

1// Good - single transaction
2db.beginWrites();
3for (Article article : articles) {
4    db.save(article.getState());
5}
6db.commitWrites();
7
8// Bad - multiple transactions
9for (Article article : articles) {
10    db.save(article.getState());
11}

Use pagination

1// Good - loads 10 items
2query.select(0, 10);
3
4// Bad - loads everything
5query.selectAll();

Use count() instead of loading all

1// Good
2long count = query.count();
3
4// Bad
5long badCount = query.selectAll().size();

Use readIterable for large datasets

1// Good - memory efficient
2for (Article article : db.readIterable(query, 100)) {
3    process(article);
4}
5
6// Bad - loads everything into memory
7List<Article> all = db.readAll(query);
8for (Article article : all) {
9    process(article);
10}

Use specific predicates

1// Good - uses index efficiently
2Query.from(Article.class)
3    .where("publishDate > ?", cutoffDate);
4
5// Less efficient - may scan more rows
6Query.from(Article.class)
7    .where("publishDate != missing");

Bulk import

1Database db = Database.Static.getDefault();
2db.beginWrites();
3
4try {
5    for (ArticleData articleData : data) {
6        Article article = new Article();
7        article.setTitle(articleData.getTitle());
8        article.setContent(articleData.getContent());
9        // ... set other fields
10
11        db.save(article.getState());
12    }
13
14    db.commitWrites();
15    System.out.println("Imported " + data.size() + " articles");
16
17} catch (Exception e) {
18    // Transaction will be rolled back
19    System.err.println("Import failed: " + e.getMessage());
20    throw e;
21} finally {
22    db.endWrites();
23}

Streaming export

1Database db = Database.Static.getDefault();
2CSVWriter csv = new CSVWriter(writer);
3
4// Write header
5csv.writeNext(new String[] { "ID", "Title", "Author", "Date" });
6
7// Stream results
8Query<Article> query = Query.from(Article.class)
9    .sortDescending("publishDate");
10
11for (Article article : db.readIterable(query, 100)) {
12    csv.writeNext(new String[] {
13        article.getId().toString(),
14        article.getTitle(),
15        article.getAuthor().getName(),
16        article.getPublishDate().toString()
17    });
18}
19
20csv.close();

Common pitfalls

Forgetting to index

1// This will fail if 'title' is not indexed
2// Query.from(Article.class)
3//     .where("title = ?", "Getting Started")
4//     .selectAll();
5// ERROR: Field 'title' is not indexed

Loading too much data

1// Avoid loading thousands of objects at once
2// List<Article> all = Query.from(Article.class).selectAll();
3// Use pagination or iterable() instead

Inefficient filtering

1// Bad - loads everything then filters in memory
2List<Article> all = Query.from(Article.class).selectAll();
3List<Article> filtered = all.stream()
4    .filter(a -> a.getPublishDate().after(cutoffDate))
5    .collect(Collectors.toList());
6
7// Good - filters at database level
8List<Article> goodFiltered = Query.from(Article.class)
9    .where("publishDate > ?", cutoffDate)
10    .selectAll();

Not handling null results

1// Bad - can throw NullPointerException
2Article article = Query.from(Article.class)
3    .where("_id = ?", id)
4    .first();
5// String title = article.getTitle();  // NPE if article is null
6
7// Good - check for null
8Article safeArticle = Query.from(Article.class)
9    .where("_id = ?", id)
10    .first();
11if (safeArticle != null) {
12    String title = safeArticle.getTitle();
13}
14
15// Or use Optional
16String optionalTitle = Query.from(Article.class)
17    .where("_id = ?", id)
18    .findFirst()
19    .map(Article::getTitle)
20    .orElse("Untitled");

Error handling

ValidationException

1try {
2    article.save();
3} catch (ValidationException e) {
4    for (State state : e.getStates()) {
5        for (ObjectField field : state.getErrorFields()) {
6            String fieldName = field.getInternalName();
7            for (Throwable error : state.getFieldErrors(field)) {
8                System.err.println("Validation error in " + fieldName + ": " + error.getMessage());
9            }
10        }
11    }
12}

Practical examples​

Search with filters​

Dynamic query building​

Related content​

Faceted search​

Soft delete pattern​

Cascading delete​

Cache invalidation with notifiers​

Query API​

Query construction​

Predicates and filtering​

where - initial predicate​

and - add AND conditions​

or - add OR conditions​

not - negate conditions​

having - filter without affecting ranking​

Predicate operators​

Equality operators​

Comparison operators​

String operators​

Collection operators​

Range queries​

Full-text search​

Special field keys​

Path-based field access​

Sorting​

sortAscending​

sortDescending​

Sort by relevance​

Sort by newest/oldest​

Multiple sort criteria​

Query execution​

selectAll​

select (pagination)​

first​

findFirst (Optional)​

count​

iterable​

deleteAll​

Grouping and aggregation​

groupBy​

Filtering grouped results​

Aggregation functions​

Query modifiers​

timeout​

noCache​

master​

resolveToReferenceOnly​

resolveInvisible​

option​

comment​

Subqueries​

Write operations​

save​

saveUnsafely​

delete​

deleteByQuery​

Database interface​

Getting a database instance​

Default database​

Named database​

All databases​

By type​

Temporary override​

Read methods​

readAll​

readFirst​

readCount​

readPartial​

readIterable​

readAllGrouped​

readPartialGrouped​

readLastUpdate​

Index operations​

index​

indexAll​

recalculate​

Batch operations​

Batch reads​

Batch writes​

Practical examples

Search with filters

Dynamic query building

Related content

Faceted search

Soft delete pattern

Cascading delete

Cache invalidation with notifiers

Query API

Query construction

Predicates and filtering

where - initial predicate

and - add AND conditions

or - add OR conditions

not - negate conditions

having - filter without affecting ranking

Predicate operators

Equality operators

Comparison operators

String operators

Collection operators

Range queries

Full-text search

Special field keys

Path-based field access

Sorting

sortAscending

sortDescending

Sort by relevance

Sort by newest/oldest

Multiple sort criteria

Query execution

selectAll

select (pagination)

first

findFirst (Optional)

count

iterable

deleteAll

Grouping and aggregation

groupBy

Filtering grouped results

Aggregation functions

Query modifiers

timeout

noCache

master

resolveToReferenceOnly

resolveInvisible

option

comment

Subqueries

Write operations

save

saveUnsafely

delete

deleteByQuery

Database interface

Getting a database instance

Default database

Named database

All databases

By type

Temporary override

Read methods

readAll

readFirst

readCount

readPartial

readIterable

readAllGrouped

readPartialGrouped

readLastUpdate

Index operations

index

indexAll

recalculate

Batch operations

Batch reads

Batch writes