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|
package trino
import (
"database/sql"
"fmt"
"strings"
"github.com/xo/usql/drivers/metadata"
)
type metaReader struct {
metadata.LoggingReader
}
var _ metadata.CatalogReader = &metaReader{}
var _ metadata.ColumnStatReader = &metaReader{}
func (r metaReader) Catalogs(metadata.Filter) (*metadata.CatalogSet, error) {
qstr := `SHOW catalogs`
rows, closeRows, err := r.Query(qstr)
if err != nil {
return nil, err
}
defer closeRows()
results := []metadata.Catalog{}
for rows.Next() {
rec := metadata.Catalog{}
err = rows.Scan(&rec.Catalog)
if err != nil {
return nil, err
}
results = append(results, rec)
}
if rows.Err() != nil {
return nil, rows.Err()
}
return metadata.NewCatalogSet(results), nil
}
func (r metaReader) ColumnStats(f metadata.Filter) (*metadata.ColumnStatSet, error) {
names := []string{}
if f.Catalog != "" {
names = append(names, f.Catalog+".")
}
if f.Schema != "" {
names = append(names, f.Schema+".")
}
names = append(names, f.Parent)
rows, closeRows, err := r.Query(fmt.Sprintf("SHOW STATS FOR %s", strings.Join(names, "")))
if err != nil {
return nil, err
}
defer closeRows()
results := []metadata.ColumnStat{}
for rows.Next() {
rec := metadata.ColumnStat{Catalog: f.Catalog, Schema: f.Schema, Table: f.Parent}
name := sql.NullString{}
avgWidth := sql.NullInt32{}
numDistinct := sql.NullInt64{}
nullFrac := sql.NullFloat64{}
numRows := sql.NullInt64{}
min := sql.NullString{}
max := sql.NullString{}
err = rows.Scan(
&name,
&avgWidth,
&numDistinct,
&nullFrac,
&numRows,
&min,
&max,
)
if err != nil {
return nil, err
}
if !name.Valid {
continue
}
rec.Name = name.String
if avgWidth.Valid {
rec.AvgWidth = int(avgWidth.Int32)
}
if numDistinct.Valid {
rec.NumDistinct = numDistinct.Int64
}
if nullFrac.Valid {
rec.NullFrac = nullFrac.Float64
}
if min.Valid {
rec.Min = min.String
}
if max.Valid {
rec.Max = max.String
}
results = append(results, rec)
}
if rows.Err() != nil {
return nil, rows.Err()
}
return metadata.NewColumnStatSet(results), nil
}
|
