Added a scripts execution ability

pkg/writers/sqlexec/README.md

@@ -0,0 +1,226 @@
+# SQL Executor Writer
+
+The SQL Executor Writer (`sqlexec`) executes SQL scripts from `models.Script` objects against a PostgreSQL database. Scripts are executed in order based on Priority (ascending) and Sequence (ascending).
+
+## Features
+
+- **Ordered Execution**: Scripts execute in Priority→Sequence order
+- **PostgreSQL Support**: Uses `pgx/v5` driver for robust PostgreSQL connectivity
+- **Stop on Error**: Execution halts immediately on first error (default behavior)
+- **Progress Reporting**: Prints execution status to stdout
+- **Multiple Schemas**: Can execute scripts from multiple schemas in a database
+
+## Usage
+
+### Basic Usage
+
+```go
+import (
+    "git.warky.dev/wdevs/relspecgo/pkg/writers"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers/sqlexec"
+)
+
+writer := sqlexec.NewWriter(&writers.WriterOptions{
+    Metadata: map[string]any{
+        "connection_string": "postgres://user:password@localhost:5432/dbname?sslmode=disable",
+    },
+})
+
+// Execute all scripts from database
+err := writer.WriteDatabase(database)
+if err != nil {
+    log.Fatalf("Execution failed: %v", err)
+}
+```
+
+### Execute Single Schema
+
+```go
+err := writer.WriteSchema(schema)
+if err != nil {
+    log.Fatalf("Schema execution failed: %v", err)
+}
+```
+
+### Complete Example with SQL Directory Reader
+
+```go
+import (
+    "log"
+    "git.warky.dev/wdevs/relspecgo/pkg/readers"
+    "git.warky.dev/wdevs/relspecgo/pkg/readers/sqldir"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers/sqlexec"
+)
+
+func main() {
+    // Read SQL scripts from directory
+    reader := sqldir.NewReader(&readers.ReaderOptions{
+        FilePath: "./migrations",
+    })
+
+    db, err := reader.ReadDatabase()
+    if err != nil {
+        log.Fatal(err)
+    }
+
+    // Execute scripts against PostgreSQL
+    writer := sqlexec.NewWriter(&writers.WriterOptions{
+        Metadata: map[string]any{
+            "connection_string": "postgres://localhost/myapp",
+        },
+    })
+
+    if err := writer.WriteDatabase(db); err != nil {
+        log.Fatal(err)
+    }
+}
+```
+
+## Configuration
+
+### Required Metadata
+
+- **connection_string**: PostgreSQL connection string (required)
+
+### Connection String Format
+
+```
+postgres://[user[:password]@][host][:port][/dbname][?param1=value1&...]
+```
+
+Examples:
+```
+postgres://localhost/mydb
+postgres://user:pass@localhost:5432/mydb?sslmode=disable
+postgres://user@localhost/mydb?sslmode=require
+postgresql://user:pass@prod-db.example.com:5432/production
+```
+
+## Execution Order
+
+Scripts are sorted and executed based on:
+
+1. **Priority** (ascending): Lower priority values execute first
+2. **Sequence** (ascending): Within same priority, lower sequence values execute first
+
+### Example Execution Order
+
+Given these scripts:
+```
+Script A: Priority=2, Sequence=1
+Script B: Priority=1, Sequence=3
+Script C: Priority=1, Sequence=1
+Script D: Priority=1, Sequence=2
+Script E: Priority=3, Sequence=1
+```
+
+Execution order: **C → D → B → A → E**
+
+## Output
+
+The writer prints progress to stdout:
+
+```
+Executing script: create_users (Priority=1, Sequence=1)
+✓ Successfully executed: create_users
+Executing script: create_posts (Priority=1, Sequence=2)
+✓ Successfully executed: create_posts
+Executing script: add_indexes (Priority=2, Sequence=1)
+✓ Successfully executed: add_indexes
+```
+
+## Error Handling
+
+### Connection Errors
+
+If the database connection fails, execution stops immediately:
+
+```
+Error: failed to connect to database: connection refused
+```
+
+### Script Execution Errors
+
+If a script fails, execution stops and returns the error with context:
+
+```
+Error: failed to execute script add_indexes (Priority=2, Sequence=1):
+       syntax error at or near "IDNEX"
+```
+
+**Behavior**: Stop on first error (scripts executed before the error remain committed)
+
+### Empty Script Handling
+
+Scripts with empty SQL content are skipped silently.
+
+## Database Support
+
+Currently supports:
+- ✅ PostgreSQL (via pgx/v5)
+
+Future support planned for:
+- MySQL/MariaDB
+- SQLite
+- Generic SQL via database/sql
+
+## Transaction Behavior
+
+**Current**: Each script executes in its own implicit transaction (PostgreSQL default behavior)
+
+**Future Enhancement**: Option to wrap all scripts in a single transaction for atomic execution with rollback on error.
+
+## Performance Considerations
+
+- Scripts execute sequentially (not in parallel)
+- Each script creates a database round-trip
+- For large migrations, consider:
+  - Combining related statements into fewer scripts
+  - Using PostgreSQL's COPY command for bulk data
+  - Running during low-traffic periods
+
+## Testing
+
+Run tests:
+```bash
+go test ./pkg/writers/sqlexec/
+```
+
+Current tests include:
+- Validation and error handling
+- Script sorting logic
+- Configuration validation
+
+### Integration Tests
+
+For integration testing with a real database:
+
+```bash
+# Start PostgreSQL (example with Docker)
+docker run -d --name postgres-test \
+  -e POSTGRES_PASSWORD=test \
+  -e POSTGRES_DB=testdb \
+  -p 5432:5432 \
+  postgres:16
+
+# Run your integration tests
+go test -tags=integration ./pkg/writers/sqlexec/
+
+# Cleanup
+docker stop postgres-test
+docker rm postgres-test
+```
+
+## Limitations
+
+- `WriteTable()` is not supported (returns error)
+- Requires PostgreSQL connection (no offline mode)
+- No built-in transaction wrapping (yet)
+- No rollback script support (yet, though `models.Script.Rollback` field exists)
+
+## Related
+
+- **SQL Directory Reader**: `pkg/readers/sqldir/` - Read scripts from filesystem
+- **Script Model**: `pkg/models/models.go` - Script structure definition
+- **pgx Documentation**: https://github.com/jackc/pgx - PostgreSQL driver docs