Support Qualified Table Names in ON Clauses

[mathiasrw]

Fix: Support Qualified Table Names in ON Clauses

Problem

The Alasql parser was incorrectly parsing three-part column references (e.g., database.table.column) in ON clauses. It treated them as a two-part column reference (database.table) followed by a property access (-> column), leading to runtime errors like TypeError: undefined is not an object.

Solution

We modified the Jison grammar to resolve a shift/reduce conflict, ensuring that database.table.column is parsed as a single Column node.

1. Parser Grammar Update

We added a low-precedence token %nonassoc LOW_PREC and applied it to the Literal DOT Literal rule in Column definition. This forces the parser to shift the second dot when encountering a.b.c, correctly identifying it as a three-part identifier.

// src/alasqlparser.jison

%nonassoc LOW_PREC
%left COMMA
// ...

Column
        : Literal DOT Literal DOT Literal
                { $$ = new yy.Column({columnid: $5, tableid: $3, databaseid:$1});}
        | Literal DOT Literal %prec LOW_PREC
                { $$ = new yy.Column({columnid: $3, tableid: $1});}
    // ...

2. Test Refactoring

We refactored test/test407.test.js to use fully qualified table names in all queries, ensuring isolated database contexts and verifying the fix.

// test/test407.test.js

// Before
'SELECT one.id AS a ... FROM one INNER JOIN two ...'

// After
'SELECT test407.one.id AS a ... FROM test407.one INNER JOIN test407.two ...'

3. Regression Test

We created a new regression test file test/test2186.test.js to verify that the fix works for both qualified and unqualified table names, with and without USE <DB> statements. We used table names A_2186 and B_2186 to avoid collisions. This ensures that future changes do not break this functionality.

Verification

We verified the fix by:

1. Running bun run jison to rebuild the parser.
2. Running bun run build to build the project.
3. Running bun test test/test407.test.js (passed).
4. Running bun test test/test2186.test.js (passed).
5. Running the full test suite bun run tst (passed with no regressions).