add query package and tool

cmd/query/main.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"github.com/aaronland/go-sqlite/database"
+	"github.com/aaronland/go-sqlite/query"
+	"log"
+	"os"
+)
+
+func main() {
+
+	dsn := flag.String("dsn", "", "A valid SQLite DSN")
+	query_str := flag.String("query", "", "A valid SQL query")
+
+	flag.Parse()
+
+	ctx := context.Background()
+
+	db, err := database.NewDB(ctx, *dsn)
+
+	if err != nil {
+		log.Fatalf("Failed to create new database, %v", err)
+	}
+
+	conn, err := db.Conn()
+
+	if err != nil {
+		log.Fatalf("Failed to get database connection, %v", err)
+	}
+
+	rows, err := conn.Query(*query_str)
+
+	if err != nil {
+		log.Fatalf("query err: %s", err)
+	}
+
+	wr, err := query.NewCSVQueryWriter(ctx, os.Stdout)
+
+	if err != nil {
+		log.Fatalf("Failed to create query writer, %v", err)
+	}
+
+	err = query.WriteRows(ctx, wr, rows)
+
+	if err != nil {
+		log.Fatalf("Failed to write rows, %v", err)
+	}
+}

database/database.go

@@ -5,11 +5,11 @@ import (
 	"database/sql"
 	"fmt"
 	_ "github.com/mattn/go-sqlite3"
+	"github.com/psanford/sqlite3vfs"
+	"github.com/psanford/sqlite3vfshttp"
 	_ "log"
 	"strings"
 	"sync"
-	"github.com/psanford/sqlite3vfshttp"
-	"github.com/psanford/sqlite3vfs"
 )
 
 type SQLiteDatabase struct {
@@ -43,13 +43,13 @@ func NewDBWithDriver(ctx context.Context, driver string, dsn string) (*SQLiteDat
 			}
 
 			err := sqlite3vfs.RegisterVFS("httpvfs", &vfs)
-			
+
 			if err != nil {
 				return nil, err
 			}
 
 			dsn = "not_a_real_name.db?vfs=httpvfs&mode=ro"
-			
+
 		} else {
 
 			// https://github.com/mattn/go-sqlite3/issues/39

query/csvwriter.go

@@ -0,0 +1,35 @@
+package query
+
+import (
+	"context"
+	"encoding/csv"
+	"io"
+)
+
+type CSVQueryWriter struct {
+	QueryWriter
+	csv_writer *csv.Writer
+}
+
+func NewCSVQueryWriter(ctx context.Context, wr io.Writer) (QueryWriter, error) {
+
+	csv_wr := csv.NewWriter(wr)
+
+	query_wr := &CSVQueryWriter{
+		csv_writer: csv_wr,
+	}
+
+	return query_wr, nil
+}
+
+func (query_wr *CSVQueryWriter) WriteRow(ctx context.Context, row []string) error {
+
+	err := query_wr.csv_writer.Write(row)
+
+	if err != nil {
+		return err
+	}
+
+	query_wr.csv_writer.Flush()
+	return nil
+}

query/writer.go

@@ -0,0 +1,66 @@
+package query
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+)
+
+type QueryWriter interface {
+	WriteRow(context.Context, []string) error
+}
+
+// The guts of this (minus the QueryWriter stuff) are copied from:
+// https://github.com/psanford/sqlite3vfshttp/blob/main/sqlitehttpcli/sqlitehttpcli.go
+
+func WriteRows(ctx context.Context, wr QueryWriter, rows *sql.Rows) error {
+
+	cols, err := rows.Columns()
+
+	if err != nil {
+		return fmt.Errorf("Failed to determine columns for rows, %v", err)
+	}
+
+	for rows.Next() {
+
+		rows.Columns()
+
+		columns := make([]*string, len(cols))
+
+		columnPointers := make([]interface{}, len(cols))
+
+		for i := range columns {
+			columnPointers[i] = &columns[i]
+		}
+
+		err = rows.Scan(columnPointers...)
+
+		if err != nil {
+			return fmt.Errorf("Failed to scan row, %w", err)
+		}
+
+		names := make([]string, 0, len(columns))
+
+		for _, col := range columns {
+			if col == nil {
+				names = append(names, "NULL")
+			} else {
+				names = append(names, *col)
+			}
+		}
+
+		err = wr.WriteRow(ctx, names)
+
+		if err != nil {
+			return fmt.Errorf("Failed to write row, %v", err)
+		}
+	}
+
+	err = rows.Close()
+
+	if err != nil {
+		return fmt.Errorf("Failed to close rows, %v", err)
+	}
+
+	return nil
+}