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Interactive REPL

jsonlogic2sql includes an interactive REPL (Read-Eval-Print Loop) for testing JSON Logic expressions.

Running the REPL

# Build and run
make run

# Or build manually
go build -o bin/repl ./cmd/repl
./bin/repl

On startup, the REPL will prompt for an optional schema path. Leave it empty to skip.

Basic Usage

jsonlogic> {">": [{"var": "amount"}, 1000]}
SQL: WHERE amount > 1000

jsonlogic> {"and": [{"==": [{"var": "status"}, "active"]}, {">": [{"var": "count"}, 5]}]}
SQL: WHERE (status = 'active' AND count > 5)

Commands

Command Description
:help Show available commands
:examples Show example JSON Logic expressions
:dialect Change the SQL dialect
:params Toggle parameterized query output (bind placeholders)
:schema <path> Load a schema JSON file for validation
:file <path> Read JSON Logic from a file
:clear Clear the screen
:quit Exit the REPL

Changing Dialects

Use :dialect to switch between SQL dialects:

[BigQuery] jsonlogic> :dialect
Select dialect:
1. BigQuery
2. Spanner
3. PostgreSQL
4. DuckDB
5. ClickHouse
Enter choice (1-5): 3

[PostgreSQL] jsonlogic> {"merge": [{"var": "a"}, {"var": "b"}]}
SQL: WHERE (a || b)

The prompt shows the current dialect in brackets.

Parameterized Output

Use :params to toggle parameterized query mode. When enabled, the output uses bind placeholders instead of inlined literals:

[BigQuery] jsonlogic> :params
Parameterized mode: ON (output uses bind placeholders)

[BigQuery] jsonlogic> {"and": [{"==": [{"var": "status"}, "active"]}, {">": [{"var": "amount"}, 1000]}]}
SQL:    WHERE (status = @p1 AND amount > @p2)
Params: [{p1: "active"}, {p2: 1000}]

[BigQuery] jsonlogic> :params
Parameterized mode: OFF (output uses inlined literals)

[BigQuery] jsonlogic> {"and": [{"==": [{"var": "status"}, "active"]}, {">": [{"var": "amount"}, 1000]}]}
SQL: WHERE (status = 'active' AND amount > 1000)

Placeholder styles vary by dialect (@p1 for BigQuery/Spanner/ClickHouse, $1 for PostgreSQL/DuckDB). See Parameterized Queries for details.

Pattern-Matching Note (LIKE)

In parameterized mode, pattern operators (for example startsWith, endsWith, contains) must keep placeholders outside string literals.

  • Correct: LIKE CONCAT(@p1, '%')
  • Incorrect: LIKE '@p1%'

The correct form preserves bind semantics; the incorrect form treats the placeholder text as a literal string.

Large JSON Input

For JSON Logic expressions larger than terminal line limits (~4KB), use the :file command:

# Save your large JSON to a file
echo '{"and": [...very large JSON...]}' > input.json

# In the REPL, load it with :file
[BigQuery] jsonlogic> :file input.json
SQL: WHERE (...)

Loading a Schema

Use :schema to load a schema file for field validation and type-aware SQL:

[BigQuery] jsonlogic> :schema schema.json
Schema loaded: schema.json

Examples Command

The :examples command shows common JSON Logic patterns:

jsonlogic> :examples
Example JSON Logic expressions:

1. Simple Comparison
   JSON: {">": [{"var": "amount"}, 1000]}
   SQL:  WHERE amount > 1000

2. Equality Check
   JSON: {"==": [{"var": "status"}, "active"]}
   SQL:  WHERE status = 'active'

3. Logical AND
   JSON: {"and": [{">": [{"var": "a"}, 10]}, {"<": [{"var": "b"}, 20]}]}
   SQL:  WHERE (a > 10 AND b < 20)

...

Error Messages

The REPL displays helpful error messages:

jsonlogic> {"unknownOp": [1, 2]}
Error: [E100] at $.unknownOp (operator: unknownOp): unsupported operator: unknownOp

jsonlogic> {invalid json}
Error: [E007]: invalid JSON: invalid character 'i' looking for beginning of object key string

Tips

  1. Use :examples first - Learn common patterns before writing your own
  2. Check dialect - Some operators generate different SQL per dialect
  3. Use :file for complex JSON - Avoids terminal line limits
  4. Copy SQL output - Use it directly in your database queries

See Also