fix: SQLite vector table now respects OM_VECTOR_TABLE env variable

[fparrav]

Summary

Fixes SQLite backend ignoring the OM_VECTOR_TABLE environment variable, causing "no such table" errors on fresh Docker installs.

Problem

• docker-compose.yml sets OM_VECTOR_TABLE=openmemory_vectors by default
• SQLite was hardcoding the table name as vectors (ignoring the env variable)
• VectorStore tried to use openmemory_vectors (from env)
• Result: SQLITE_ERROR: no such table: openmemory_vectors

PostgreSQL already respected this env variable correctly.

Solution

Make SQLite table creation and index use the OM_VECTOR_TABLE env variable, with vectors as the default for backward compatibility with existing databases.

Changes

• backend/src/core/db.ts:
  • Read OM_VECTOR_TABLE env variable (default: vectors)
  • Use variable in table creation instead of hardcoded name
  • Use variable in index creation
  • Use same variable for VectorStore initialization

Testing

1. Fresh Docker install with default config now works
2. Existing SQLite databases with vectors table still work (backward compatible)
3. TypeScript compiles without errors

[Copilot]

Pull request overview

This PR fixes a critical bug where the SQLite backend was ignoring the OM_VECTOR_TABLE environment variable, causing "no such table" errors in fresh Docker installations. The fix ensures SQLite respects the environment variable while maintaining backward compatibility with existing databases.

• Reads OM_VECTOR_TABLE environment variable with vectors as default for backward compatibility
• Updates SQLite table creation and index creation to use the configurable table name
• Aligns SQLite behavior with PostgreSQL, which already respected this environment variable

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The table name from the environment variable is directly interpolated into the SQL statement without proper escaping or validation. While PostgreSQL uses quoted identifiers (line 92), SQLite does not, potentially allowing SQL injection if OM_VECTOR_TABLE contains malicious input like vectors; DROP TABLE memories--.

Consider either:

1. Adding validation to ensure the table name contains only safe characters (alphanumeric and underscores)
2. Using quoted identifiers similar to PostgreSQL: `create table if not exists "${sqlite_vector_table}"(...)`

Example validation:

const sqlite_vector_table = process.env.OM_VECTOR_TABLE || "vectors";
if (!/^[a-zA-Z_][a-zA-Z0-9_]*$/.test(sqlite_vector_table)) {
    throw new Error(`Invalid table name: ${sqlite_vector_table}`);
}

[Copilot]

The table name from the environment variable is directly interpolated into the SQL statement without proper escaping or validation. This creates the same SQL injection vulnerability as the table creation statement.

Apply the same validation or escaping approach as recommended for the table creation to ensure consistency and security.