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query_engine.go
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/
query_engine.go
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package xisdb
import "github.com/alexsward/xisdb/ql"
// QueryEngine is the processor of xisql statements
type QueryEngine struct {
}
// QueryEngineContext is the context of what the engine should perform the query in
type QueryEngineContext struct {
DB *DB
Results chan Item
// errors chan<- error
}
// Execute will perform all of the statements in the context of the QueryEngineContext
func (qe *QueryEngine) Execute(statements []ql.Statement, ctx *QueryEngineContext) error {
if ctx.DB == nil {
return ErrNoDatabase
}
go func() error {
defer close(ctx.Results)
for _, statement := range statements {
if err := statement.Validate(); err != nil {
return err
}
switch statement.(type) {
case *ql.GetStatement:
s := statement.(*ql.GetStatement)
for _, key := range s.Keys() {
item, err := ctx.DB.Get(key)
if err != nil {
return err
}
ctx.Results <- Item{key, item, nil}
}
return nil
case *ql.SetStatement:
s := statement.(*ql.SetStatement)
return ctx.DB.ReadWrite(func(tx *Tx) error {
for key, value := range s.Pairs() {
err := tx.Set(key, value, nil)
if err != nil {
return err
}
ctx.Results <- Item{key, value, nil}
}
return nil
})
case *ql.DelStatement:
s := statement.(*ql.DelStatement)
return ctx.DB.ReadWrite(func(tx *Tx) error {
for _, key := range s.Keys() {
_, err := tx.Delete(key)
if err != nil {
return err
}
ctx.Results <- Item{key, "", nil}
}
return nil
})
}
}
return nil
}()
return nil
}