Bug: Persistent FTS index on an empty node table causes hash_index.cpp assertion after reopen

[sify21]

Ladybug version

Rust crate: lbug = 0.16.1

What operating system are you using?

Ubuntu 24.04

What happened?

Creating a persistent FTS index on an empty node table succeeds, but after closing the process and reopening the
database from a new process, even a normal MATCH query fails with an internal assertion:

Assertion failed in file ".../lbug-src/src/storage/index/hash_index.cpp" on line 483:
hashIndexStorageInfo.overflowHeaderPage == INVALID_PAGE_IDX

This is different from #438: LOAD EXTENSION FTS succeeds when the Rust host binary is built with -rdynamic. The
failure happens after reopening a database that contains an FTS index created on an empty node table.

Are there known steps to reproduce?

Minimal Rust Reproduction

Cargo.toml:

[package]
name = "lbug_empty_fts_repro"
version = "0.1.0"
edition = "2021"
build = "build.rs"

[dependencies]
lbug = "0.16.1"

build.rs:

fn main() {
    // Needed for LadybugDB dynamic extensions to resolve symbols from the Rust host binary.
    println!("cargo:rustc-link-arg=-rdynamic");
}

src/main.rs:

use std::{env, process};

fn main() {
    if let Err(err) = run() {
        eprintln!("{err}");
        process::exit(1);
    }
}

fn run() -> Result<(), Box<dyn std::error::Error>> {
    let mut args = env::args().skip(1);
    let db_path = args.next().unwrap_or_else(|| "/tmp/lbug-empty-fts.db".to_string());
    let mode = args.next().unwrap_or_else(|| "create-empty-index".to_string());

    let db = lbug::Database::new(&db_path, lbug::SystemConfig::default())?;
    let conn = lbug::Connection::new(&db)?;

    match mode.as_str() {
        "create-empty-index" => {
            conn.query(
                "CREATE NODE TABLE IF NOT EXISTS TestNode (
                    id STRING,
                    name STRING,
                    body STRING,
                    PRIMARY KEY(id)
                );",
            )?;
            conn.query("INSTALL FTS;")?;
            conn.query("LOAD EXTENSION FTS;")?;
            conn.query(
                "CALL CREATE_FTS_INDEX(
                    'TestNode',
                    'test_node_fts',
                    ['name', 'body'],
                    stemmer := 'porter'
                );",
            )?;
            conn.query("CHECKPOINT;")?;
            println!("created FTS index on empty table");
        }

        "reopen-query" => {
            conn.query("LOAD EXTENSION FTS;")?;
            let result = conn.query("MATCH (n:TestNode) RETURN n.id LIMIT 5;")?;
            println!("{result}");
        }

        "create-nonempty-index" => {
            conn.query(
                "CREATE NODE TABLE IF NOT EXISTS TestNode (
                    id STRING,
                    name STRING,
                    body STRING,
                    PRIMARY KEY(id)
                );",
            )?;
            conn.query("CREATE (:TestNode {id: 'n1', name: 'hello', body: 'hello world'});")?;
            conn.query("INSTALL FTS;")?;
            conn.query("LOAD EXTENSION FTS;")?;
            conn.query(
                "CALL CREATE_FTS_INDEX(
                    'TestNode',
                    'test_node_fts',
                    ['name', 'body'],
                    stemmer := 'porter'
                );",
            )?;
            conn.query("CHECKPOINT;")?;
            println!("created FTS index on non-empty table");
        }

        other => {
            return Err(format!("unknown mode: {other}").into());
        }
    }

    Ok(())
}

Steps to Reproduce

rm -f /tmp/lbug-empty-fts.db

cargo run -- /tmp/lbug-empty-fts.db create-empty-index
cargo run -- /tmp/lbug-empty-fts.db reopen-query

Actual Result

The second command fails with:

Assertion failed in file ".../lbug-src/src/storage/index/hash_index.cpp" on line 483:
hashIndexStorageInfo.overflowHeaderPage == INVALID_PAGE_IDX

Expected Result

Creating an FTS index on an empty table should either:

• be supported and reopen cleanly,
• fail gracefully when the index is created, or
• be ignored/deferred until rows exist.

It should not leave the database in a state that later triggers an internal assertion after reopen.

Control Case

If the table contains at least one row before creating the FTS index, reopening succeeds:

rm -f /tmp/lbug-empty-fts.db

cargo run -- /tmp/lbug-empty-fts.db create-nonempty-index
cargo run -- /tmp/lbug-empty-fts.db reopen-query

This suggests the issue is specific to persistent FTS indexes created on empty node tables.

Relation to #438

This is related to Rust embedding and FTS, but it is not the same failure mode:

• Bug: FTS extension fails to load on macOS arm64 from Rust static binary (missing GDSFunction symbol) #438: LOAD EXTENSION FTS fails because the host binary does not export LadybugDB symbols.
• This issue: LOAD EXTENSION FTS succeeds with -rdynamic; the failure happens after creating a persistent FTS
  index on an empty table and reopening the database.

[adsharma]

I can't repro with:

lbug test.db < create_empty_fts.cypher
lbug test.db < reopen_query.cypher

Also ran your rust repro 3 times on ubuntu 24.04. Doesn't repro for me.

[adsharma]

create_empty_fts.txt
reopen_query.txt

[sify21]

@adsharma I forgot to mention that I need to build lbug from source, or else it will report a lot of rust-lld error

.cargo/config.toml:

[env]
# The lbug 0.16.1 prebuilt static archive does not include all native
# third-party dependencies needed at link time on Linux (for example
# roaring_bitmap and antlr4_cypher). Building from bundled source lets the
# crate link its complete dependency set.
LBUG_BUILD_FROM_SOURCE = "1"

In my environment it reproduces each time

My rust version is cargo 1.94.1 (29ea6fb6a 2026-03-24)

[adsharma]

Yes - I built from source as well. Tested on both macos/arm64 and ubuntu 24.04/x64.

cargo 1.93.1 (083ac5135 2025-12-15)

Can you build a shell in your env (make shell in the ladybug source tree) and see if it repros?

If shell doesn't repro, but rust repros, it narrows the problems to rust bindings.

[sify21]

@adsharma Running lbug in build/release/tools/shell doesn't report error. The shell is built using tag v0.16.1

❯ ./lbug /tmp/lbug-empty-fts.db < create_empty_fts.txt
Opening the database at path: /tmp/lbug-empty-fts.db in read-write mode.
Enter ":help" for usage hints.
┌──────────────────────────────────┐
│ result                           │
│ STRING                           │
├──────────────────────────────────┤
│ Table TestNode has been created. │
└──────────────────────────────────┘
(1 tuple)
(1 column)
Time: 3.37ms (compiling), 9.28ms (executing)
┌────────────────────────────────────────────────────────────────────────────┐
│ result                                                                     │
│ STRING                                                                     │
├────────────────────────────────────────────────────────────────────────────┤
│ Extension: fts is already installed.
To update it, you can run: UPDATE fts. │
└────────────────────────────────────────────────────────────────────────────┘
(1 tuple)
(1 column)
Time: 0.15ms (compiling), 6.36ms (executing)
┌─────────────────────────────────┐
│ result                          │
│ STRING                          │
├─────────────────────────────────┤
│ Extension: fts has been loaded. │
└─────────────────────────────────┘
(1 tuple)
(1 column)
Time: 0.18ms (compiling), 9.02ms (executing)
┌───────────────────────────────────────┐
│ result                                │
│ STRING                                │
├───────────────────────────────────────┤
│ Index test_node_fts has been created. │
└───────────────────────────────────────┘
(1 tuple)
(1 column)
Time: 233.00ms (compiling), 426.24ms (executing)
(0 tuples)
(0 columns)
Time: 0.09ms (compiling), 21.83ms (executing)

❯ ./lbug /tmp/lbug-empty-fts.db < reopen_query.txt    
Opening the database at path: /tmp/lbug-empty-fts.db in read-write mode.
Enter ":help" for usage hints.
┌─────────────────────────────────┐
│ result                          │
│ STRING                          │
├─────────────────────────────────┤
│ Extension: fts has been loaded. │
└─────────────────────────────────┘
(1 tuple)
(1 column)
Time: 3.01ms (compiling), 7.81ms (executing)
┌────────┐
│ n.id   │
│ STRING │
├────────┤
└────────┘
(0 tuples)
(1 column)
Time: 8.33ms (compiling), 0.77ms (executing)

[adsharma]

Merged LadybugDB/extensions#1. Concurrent access to the unordered_map could be the root cause. Please retest when 0.17.x is released.