add new db interface beginnings

1 files changed, 91 insertions, 0 deletions

diff --git a/database/postgres/create_table.go b/database/postgres/create_table.go
new file mode 100644
index 0000000..31da112
--- /dev/null
+++ b/database/postgres/create_table.go
@@ -0,0 +1,91 @@
+package postgres
+
+import (
+	"database/sql"
+	"fmt"
+	"strings"
+)
+
+// sql query
+type sqlQuery struct {
+	query  string
+	params []interface{}
+}
+
+func (q *sqlQuery) Exec(conn *sql.DB) (err error) {
+	_, err = conn.Exec(q.query, q.params...)
+	return
+}
+
+func (q *sqlQuery) QueryRow(conn *sql.DB, visitor func(*sql.Row) error) (err error) {
+	err = visitor(conn.QueryRow(q.query, q.params))
+	return
+}
+
+func (q *sqlQuery) Query(conn *sql.DB, visitor func(*sql.Rows) error) (err error) {
+	var rows *sql.Rows
+	rows, err = conn.Query(q.query, q.params...)
+	if err == sql.ErrNoRows {
+		err = nil
+	} else if err == nil {
+		err = visitor(rows)
+		rows.Close()
+	}
+	return
+}
+
+// make a createQuery that creates an index for column on table
+func createIndex(table, column string) sqlQuery {
+	return sqlQuery{
+		query: fmt.Sprintf("CREATE INDEX IF NOT EXISTS ON %s %s ", table, column),
+	}
+}
+
+// make a createQuery that creates a trigraph index on a table for multiple columns
+func createTrigraph(table string, columns ...string) sqlQuery {
+	return sqlQuery{
+		query: fmt.Sprintf("CREATE INDEX IF NOT EXISTS ON %s USING gin(%s gin_trgm_ops)", table, strings.Join(columns, ", ")),
+	}
+}
+
+// defines table creation info
+type createTable struct {
+	name       string       // Table's name
+	columns    tableColumns // Table's columns
+	preCreate  []sqlQuery   // Queries to run before table is ensrued
+	postCreate []sqlQuery   // Queries to run after table is ensured
+}
+
+func (t createTable) String() string {
+	return fmt.Sprintf("CREATE TABLE %s IF NOT EXISTS ( %s )", t.name, t.columns)
+}
+
+func (t createTable) Exec(conn *sql.DB) (err error) {
+	// pre queries
+	for idx := range t.preCreate {
+		err = t.preCreate[idx].Exec(conn)
+		if err != nil {
+			return
+		}
+	}
+	// table definition
+	_, err = conn.Exec(t.String())
+	if err != nil {
+		return
+	}
+	// post queries
+	for idx := range t.postCreate {
+		err = t.postCreate[idx].Exec(conn)
+		if err != nil {
+			return
+		}
+	}
+	return
+}
+
+// tableColumns is a list of columns for a table to be created
+type tableColumns []string
+
+func (def tableColumns) String() string {
+	return strings.Join(def, ", ")
+}