A lucene parser written in go with no dependencies.
With this package you can quickly integrate lucene style searching inside your app and generate sql filters for a particular query. There are no external dependencies and the grammar fully supports Apache Lucene 9.4.2.
Out of the box go-lucene support postgres compliant sql generation but it can be extended to support different flavors of sql (or no sql) as well.
Use lucene.ToPostgres
to generate a single string with all your filters in it
Use lucene.ToParmeterizedPostgres
to generate a parameterized string with args that you can pass to your DB query
// suppose you want a query for red apples that are not honey crisp or granny smith and are older than 5 months old
myQuery := `color:red AND NOT (type:"honey crisp" OR type:"granny smith") AND age_in_months:[5 TO *]`
filter, err := lucene.ToPostgres(myQuery)
if err != nil {
// handle error
}
SQLTemplate := `
SELECT *
FROM apples
WHERE %s
LIMIT 10;
`
sqlQuery := fmt.Sprintf(SQLTemplate, filter)
// sqlQuery is:
`
SELECT *
FROM apples
WHERE
(
("color" = 'red') AND
(
NOT(
("type" = 'honey crisp') OR
("type" = 'granny smith')
)
)
) AND
("age_in_months" >= 5)
LIMIT 10;
`
// suppose you want a query for red apples that are not honey crisp or granny smith and are older than 5 months old
myQuery := `color:red AND NOT (type:"honey crisp" OR type:"granny smith") AND age_in_months:[5 TO *]`
filter, params, err := lucene.ToParameterizedPostgres(myQuery)
if err != nil {
// handle error
}
SQLTemplate := `
SELECT *
FROM apples
WHERE %s
LIMIT 10;
`
sqlQuery := fmt.Sprintf(SQLTemplate, filter)
db.Query(sqlQuery, params)
Just embed the Base
driver in your custom driver and override the RenderFN
's with your own custom rendering functions.
import (
"github.com/grindlemire/go-lucene"
"github.com/grindlemire/go-lucene/pkg/driver"
"github.com/grindlemire/go-lucene/pkg/lucene/expr"
)
type MyDriver struct {
driver.Base
}
// Suppose we want a customer driver that is postgres but uses "==" rather than "=" for an equality check.
func NewMyDriver() MyDriver {
// register your new custom render functions. Each render function
// takes a left and optionally right rendered string and returns the rendered
// output string for the entire expression.
fns := map[expr.Operator]driver.RenderFN{
expr.Equals: myEquals,
}
// iterate over the existing base render functions and swap out any that you want to
for op, sharedFN := range driver.Shared {
_, found := fns[op]
if !found {
fns[op] = sharedFN
}
}
// return the new driver ready to use
return MyDriver{
driver.Base{
RenderFNs: fns,
},
}
}
// Suppose we wanted to implement equals using a "==" operator instead of "="
func myEquals(left, right string) (string, error) {
return left + " == " + right, nil
}
...
func main() {
// create a new instance of the driver
driver := NewMyDriver()
// render an expression
expr, _ := lucene.Parse(`color:red AND NOT (type:"honey crisp" OR type:"granny smith") AND age_in_months:[5 TO *]`)
filter, _ := driver.Render(expr)
SQLTemplate := `
SELECT *
FROM apples
WHERE %s
LIMIT 10;
`
sqlQuery := fmt.Sprintf(SQLTemplate, filter)
// sqlQuery is:
`
SELECT *
FROM apples
WHERE
(
("color" == 'red') AND
(
NOT(
("type" == 'honey crisp') OR
("type" == 'granny smith')
)
)
) AND
("age_in_months" >= 5)
LIMIT 10;
`
}