SDI Extraction

The idb::innodb::sdi module provides functions for extracting Serialized Dictionary Information (SDI) from MySQL 8.0+ tablespaces. SDI replaced .frm files as the mechanism for embedding table, column, and index definitions directly inside each .ibd file. SDI data is stored on dedicated SDI pages (page type 17853) as zlib-compressed JSON.

Finding SDI Pages

use idb::innodb::tablespace::Tablespace;
use idb::innodb::sdi;

let mut ts = Tablespace::open("users.ibd").unwrap();
let sdi_pages = sdi::find_sdi_pages(&mut ts).unwrap();
println!("Found {} SDI pages: {:?}", sdi_pages.len(), sdi_pages);

find_sdi_pages uses a two-phase approach:

1. Fast path: Reads the SDI root page number from page 0 (located after the FIL header, FSP header, and XDES array). If the SDI version marker (value 1) is found and the root page is valid, it reads the root page and walks its prev/next linked list to collect all SDI leaf pages.
2. Fallback: If the fast path fails (e.g., corrupted page 0, pre-8.0 tablespace), it scans every page in the tablespace looking for SDI page types.

Extracting SDI Records

use idb::innodb::tablespace::Tablespace;
use idb::innodb::sdi;

let mut ts = Tablespace::open("users.ibd").unwrap();
let sdi_pages = sdi::find_sdi_pages(&mut ts).unwrap();
let records = sdi::extract_sdi_from_pages(&mut ts, &sdi_pages).unwrap();

for rec in &records {
    println!("Type: {} ({})", rec.sdi_type, sdi::sdi_type_name(rec.sdi_type));
    println!("Object ID: {}", rec.sdi_id);
    println!("Compressed: {} bytes -> {} bytes uncompressed",
        rec.compressed_len, rec.uncompressed_len);
    // rec.data contains the decompressed JSON string
    println!("Data (first 200 chars): {}", &rec.data[..rec.data.len().min(200)]);
    println!("---");
}

Function Signature

pub fn extract_sdi_from_pages(
    ts: &mut Tablespace,
    sdi_pages: &[u64],
) -> Result<Vec<SdiRecord>, IdbError>

The function:

1. Reads each SDI page and verifies it has page type SDI (17853)
2. Parses the INDEX page header to confirm it is a leaf page with records
3. Walks compact-format records on the page
4. For each ordinary record, extracts the SDI header fields (type, ID, lengths)
5. If compressed data fits within the page, decompresses it directly
6. If compressed data spans multiple pages, follows the next-page chain to collect all compressed bytes before decompression

SdiRecord

SDI Type Names

use idb::innodb::sdi;

assert_eq!(sdi::sdi_type_name(1), "Table");
assert_eq!(sdi::sdi_type_name(2), "Tablespace");
assert_eq!(sdi::sdi_type_name(99), "Unknown");

Checking Individual Pages

use idb::innodb::sdi;

let page_data = vec![0u8; 16384];
// Check if a page buffer is an SDI page
if sdi::is_sdi_page(&page_data) {
    // Extract records from a single page (no multi-page reassembly)
    if let Some(records) = sdi::extract_sdi_from_page(&page_data) {
        println!("Found {} SDI records on this page", records.len());
    }
}

extract_sdi_from_page works on a single page buffer without requiring a Tablespace handle. It does not follow page chains, so records spanning multiple pages may have truncated or incomplete data. Use extract_sdi_from_pages with a Tablespace for full multi-page reassembly.

Reading the SDI Root Page

For advanced use, you can read the SDI root page number directly from page 0:

use idb::innodb::tablespace::Tablespace;
use idb::innodb::sdi;

let mut ts = Tablespace::open("users.ibd").unwrap();
let page0 = ts.read_page(0).unwrap();

if let Some(root_page) = sdi::read_sdi_root_page(&page0, ts.page_size(), ts.page_count()) {
    println!("SDI root page: {}", root_page);
}

This returns None if the SDI version marker is not found, the version is not 1, or the root page number is out of range.

Limitations

• SDI is a MySQL 8.0+ feature. MariaDB tablespaces do not contain SDI pages.
• Pre-MySQL 8.0 tablespaces will return an empty list from find_sdi_pages.
• The SDI JSON schema is defined by MySQL's data dictionary and varies between MySQL versions.