internal/{database,postgres}: export CollectStrings

Export the CollectStrings function and move to the database package so
it can be used elsewhere.

Change-Id: I1032e4f5042209e42e8f0de9cebfb48653d56f69
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/336209
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/internal/database/database.go b/internal/database/database.go
index dbbde425..227ff4c0 100644
--- a/internal/database/database.go
+++ b/internal/database/database.go
@@ -535,6 +535,25 @@ func buildBulkUpdateQuery(table string, columns, types []string) string {
 	)
 }
 
+// CollectStrings runs the query, which must select for a single string column, and returns
+// a slice of the resulting strings.
+func (db *DB) CollectStrings(ctx context.Context, query string, args ...interface{}) (ss []string, err error) {
+	defer derrors.WrapStack(&err, "DB.CollectStrings(%q)", query)
+
+	err = db.RunQuery(ctx, query, func(rows *sql.Rows) error {
+		var s string
+		if err := rows.Scan(&s); err != nil {
+			return err
+		}
+		ss = append(ss, s)
+		return nil
+	}, args...)
+	if err != nil {
+		return nil, err
+	}
+	return ss, nil
+}
+
 // emptyStringScanner wraps the functionality of sql.NullString to just write
 // an empty string if the value is NULL.
 type emptyStringScanner struct {