discovery/internal/postgres: read/write to the version_logs table

The discovery/internal/postgres package is created to interact
with the discovery database. The following methods are implemented:
- LastestProxyIndexUpdate() *time.Time
- InsertNewVersionsToLog(newVersions []*internal.VersionLog) error

These will be used by the proxy index cron when fetching new versions
from the module index.

The version_log table is renamed to version_logs. This was initially
a typo.

A dependency to github.com/lib/pq v1.0.0 is introduced.

Change-Id: I720a836dc85a37a5df863e879ce6f60082c795f1
Reviewed-on: https://team-review.git.corp.google.com/c/413847
Reviewed-by: Andrew Bonventre <andybons@google.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/internal/postgres/postgres.go b/internal/postgres/postgres.go
new file mode 100644
index 00000000..cd45e6bd
--- /dev/null
+++ b/internal/postgres/postgres.go
@@ -0,0 +1,45 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package postgres
+
+import (
+	"database/sql"
+)
+
+type DB struct {
+	*sql.DB
+}
+
+func Open(dbinfo string) (*DB, error) {
+	db, err := sql.Open("postgres", dbinfo)
+	if err != nil {
+		return nil, err
+	}
+
+	if err = db.Ping(); err != nil {
+		return nil, err
+	}
+	return &DB{db}, nil
+}
+
+func (db *DB) Transact(txFunc func(*sql.Tx) error) (err error) {
+	tx, err := db.Begin()
+	if err != nil {
+		return
+	}
+
+	defer func() {
+		if p := recover(); p != nil {
+			tx.Rollback()
+			panic(p)
+		} else if err != nil {
+			tx.Rollback()
+		} else {
+			err = tx.Commit()
+		}
+	}()
+
+	return txFunc(tx)
+}