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const std = @import("std");
const varint = @import("varint.zig");
const record = @import("record.zig");
/// Search for an index by table and column name
pub fn getIndexRootpage(allocator: std.mem.Allocator, file: *std.fs.File, page_size: u16, table_name: []const u8, column_name: []const u8) !?u32 {
var buf: [2]u8 = undefined;
_ = try file.seekTo(103);
_ = try file.read(&buf);
const num_cells = std.mem.readInt(u16, &buf, .big);
if (num_cells == 0) return null;
var cell_pointers = try allocator.alloc(u16, num_cells);
defer allocator.free(cell_pointers);
for (0..num_cells) |i| {
_ = try file.seekTo(108 + i * 2);
_ = try file.read(&buf);
cell_pointers[i] = std.mem.readInt(u16, &buf, .big);
}
var page_data = try allocator.alloc(u8, page_size);
defer allocator.free(page_data);
_ = try file.seekTo(0);
_ = try file.read(page_data);
for (0..num_cells) |i| {
if (cell_pointers[i] >= page_data.len) continue;
const cell_data = page_data[cell_pointers[i]..];
var parsed = varint.parse(cell_data);
var pos = parsed.len;
if (pos >= cell_data.len) continue;
parsed = varint.parse(cell_data[pos..]);
pos += parsed.len;
if (pos >= cell_data.len) continue;
const record_data = cell_data[pos..];
parsed = varint.parse(record_data);
const header_size = parsed.value;
if (header_size > record_data.len) continue;
var header_pos = parsed.len;
var serial_types: [5]u64 = undefined;
for (0..5) |col| {
if (header_pos >= header_size) break;
parsed = varint.parse(record_data[header_pos..]);
serial_types[col] = parsed.value;
header_pos += parsed.len;
}
const type_st = serial_types[0];
const name_st = serial_types[1];
const tbl_name_st = serial_types[2];
var body_pos: usize = header_size;
const type_result = record.readString(record_data[body_pos..], type_st);
if (!std.mem.eql(u8, type_result.value, "index")) continue;
body_pos += type_result.len;
const name_result = record.readString(record_data[body_pos..], name_st);
body_pos += name_result.len;
const tbl_name_result = record.readString(record_data[body_pos..], tbl_name_st);
const expected_index_name = try std.fmt.allocPrint(allocator, "idx_{s}_{s}", .{ table_name, column_name });
defer allocator.free(expected_index_name);
if (std.mem.eql(u8, name_result.value, expected_index_name) and
std.mem.eql(u8, tbl_name_result.value, table_name))
{
body_pos += tbl_name_result.len;
const rootpage_st = serial_types[3];
const rootpage_result = record.readInt(record_data[body_pos..], rootpage_st);
return @as(u32, @intCast(rootpage_result.value));
}
}
return null;
}
/// Search index B-tree for matching values and collect rowids
pub fn searchIndexForValue(allocator: std.mem.Allocator, file: *std.fs.File, page_size: u16, index_rootpage: u32, search_value: []const u8, rowids: *std.ArrayList(u64)) !void {
// Read file into memory once
const file_size = try file.getEndPos();
const file_data = try allocator.alloc(u8, file_size);
defer allocator.free(file_data);
_ = try file.seekTo(0);
_ = try file.read(file_data);
// Use stack to iterate all pages
var stack = std.ArrayList(u32){};
defer stack.deinit(allocator);
try stack.append(allocator, index_rootpage);
while (stack.items.len > 0) {
const page_num = stack.pop() orelse continue;
if (page_num == 0) continue;
const page_offset = (page_num - 1) * @as(usize, page_size);
if (page_offset + page_size > file_data.len) continue;
const page_data = file_data[page_offset .. page_offset + page_size];
const page_type = page_data[0];
if (page_type == 0x0a) {
// Leaf index page - search for matching values
const num_cells = std.mem.readInt(u16, page_data[3..5], .big);
for (0..num_cells) |i| {
const offset = 8 + i * 2;
if (offset + 2 > page_data.len) continue;
const cell_ptr = std.mem.readInt(u16, page_data[offset..][0..2], .big);
if (cell_ptr >= page_data.len) continue;
const cell_data = page_data[cell_ptr..];
var parsed = varint.parse(cell_data);
const pos = parsed.len;
if (pos >= cell_data.len) continue;
const record_data = cell_data[pos..];
parsed = varint.parse(record_data);
const header_size = parsed.value;
if (header_size > record_data.len) continue;
var header_pos = parsed.len;
// Parse serial types
var serial_types: [8]u64 = undefined;
var num_st: usize = 0;
while (header_pos < header_size and num_st < 8) {
parsed = varint.parse(record_data[header_pos..]);
serial_types[num_st] = parsed.value;
num_st += 1;
header_pos += parsed.len;
}
if (num_st >= 2) {
const st = serial_types[0];
var body_pos: usize = header_size;
if (st >= 13 and (st % 2) == 1) {
const str_result = record.readString(record_data[body_pos..], st);
if (std.mem.eql(u8, str_result.value, search_value)) {
body_pos += str_result.len;
const rowid_st = serial_types[1];
const rowid_result = record.readInt(record_data[body_pos..], rowid_st);
try rowids.append(allocator, @as(u64, @intCast(rowid_result.value)));
}
}
}
}
} else if (page_type == 0x02) {
// Interior index page - add ALL children to stack
const num_cells = std.mem.readInt(u16, page_data[3..5], .big);
const rightmost_ptr = std.mem.readInt(u32, page_data[8..12], .big);
// Add all cell pointers
for (0..num_cells) |i| {
const offset = 12 + i * 2;
if (offset + 2 > page_data.len) continue;
const cell_ptr = std.mem.readInt(u16, page_data[offset..][0..2], .big);
if (cell_ptr + 4 > page_data.len) continue;
const cell_data = page_data[cell_ptr..];
const left_child_page = std.mem.readInt(u32, cell_data[0..4], .big);
if (left_child_page > 0) {
try stack.append(allocator, left_child_page);
}
}
if (rightmost_ptr > 0) {
try stack.append(allocator, rightmost_ptr);
}
}
}
}
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