Query Operations

Search by prefix, filter with predicates, sort entries, and iterate over ranges.

TIP

Use prefix() for efficient iteration over key patterns, and filter() for custom predicate based searches.

const std = @import("std");
const zkv = @import("zkv");

pub fn main() !void {
    var da: std.heap.DebugAllocator(.{}) = .init;
    defer _ = da.deinit();
    const allocator = da.allocator();

    var db = try zkv.Database.open(allocator, .{
        .path = "examples/query_operations.zkv",
    });
    defer db.close();

    const users = db.collection("users");
    const posts = db.collection("posts");

    try users.set("1:name", "Alice");
    try users.set("1:role", "admin");
    try users.set("2:name", "Bob");
    try users.set("2:role", "editor");
    try posts.set("1:title", "Hello");

    // Search by prefix
    var results = try db.search(.{ .prefix = "users:" });
    defer results.deinit(allocator);

    // Filter: find admins
    var admins = try db.filter(null, struct {
        fn is_admin(_: void, e: zkv.Entry) bool {
            return std.mem.eql(u8, e.value, "admin");
        }
    }.is_admin, .{});
    defer admins.deinit(allocator);

    // Iterator
    var iter = users.iterator(null, null);
    while (iter.next()) |entry| {
        std.debug.print("  {s} = {s}\n", .{ entry.key, entry.value });
    }

    // Range query
    var range_result = users.range("1:", "3:");
    defer range_result.deinit(allocator);

    // Count
    std.debug.print("Users: {}\n", .{users.count()});
    std.debug.print("Posts: {}\n", .{posts.count()});
}