feat(postgres): add postgres backend support and migration docs

2026-10-05 09:36:37 +08:00 · 2026-02-12 06:38:25 +00:00
parent 69f62188cf
commit cedcaebd1f
16 changed files with 819 additions and 53 deletions
@@ -0,0 +1,280 @@
+// Package store provides a thin dialect-aware wrapper around database/sql,
+// enabling transparent use of both SQLite and PostgreSQL.
+package store
+
+import (
+	"database/sql"
+	"fmt"
+	"strings"
+)
+
+// Dialect identifies the underlying database engine.
+type Dialect int
+
+const (
+	DialectSQLite Dialect = iota
+	DialectPostgres
+)
+
+// String returns a human-readable dialect name.
+func (d Dialect) String() string {
+	switch d {
+	case DialectSQLite:
+		return "sqlite"
+	case DialectPostgres:
+		return "postgres"
+	default:
+		return "unknown"
+	}
+}
+
+// DB wraps *sql.DB with dialect awareness.
+type DB struct {
+	raw     *sql.DB
+	dialect Dialect
+}
+
+// Wrap creates a new dialect-aware DB from an existing *sql.DB.
+func Wrap(raw *sql.DB, dialect Dialect) *DB {
+	return &DB{raw: raw, dialect: dialect}
+}
+
+// Dialect returns the database dialect.
+func (db *DB) Dialect() Dialect {
+	if db == nil {
+		return DialectSQLite
+	}
+	return db.dialect
+}
+
+// RawDB returns the underlying *sql.DB.
+func (db *DB) RawDB() *sql.DB {
+	if db == nil {
+		return nil
+	}
+	return db.raw
+}
+
+// Close closes the underlying connection.
+func (db *DB) Close() error {
+	if db == nil || db.raw == nil {
+		return nil
+	}
+	return db.raw.Close()
+}
+
+// Ping verifies the connection is alive.
+func (db *DB) Ping() error {
+	return db.raw.Ping()
+}
+
+// Exec executes a query with transparent placeholder and syntax rewriting.
+func (db *DB) Exec(query string, args ...any) (sql.Result, error) {
+	return db.raw.Exec(db.rewrite(query), args...)
+}
+
+// Query executes a query that returns rows, with transparent rewriting.
+func (db *DB) Query(query string, args ...any) (*sql.Rows, error) {
+	return db.raw.Query(db.rewrite(query), args...)
+}
+
+// QueryRow executes a query that returns at most one row, with transparent rewriting.
+func (db *DB) QueryRow(query string, args ...any) *sql.Row {
+	return db.raw.QueryRow(db.rewrite(query), args...)
+}
+
+// Begin starts a transaction, returning a dialect-aware Tx.
+func (db *DB) Begin() (*Tx, error) {
+	tx, err := db.raw.Begin()
+	if err != nil {
+		return nil, err
+	}
+	return &Tx{raw: tx, dialect: db.dialect}, nil
+}
+
+// ExecReturningID executes an INSERT and returns the auto-generated id.
+//   - SQLite: uses LastInsertId()
+//   - PostgreSQL: appends RETURNING id and uses QueryRow().Scan()
+func (db *DB) ExecReturningID(query string, args ...any) (int64, error) {
+	q := db.rewrite(query)
+	if db.dialect == DialectPostgres {
+		q = strings.TrimRight(q, "; \t\n") + " RETURNING id"
+		var id int64
+		if err := db.raw.QueryRow(q, args...).Scan(&id); err != nil {
+			return 0, err
+		}
+		return id, nil
+	}
+	res, err := db.raw.Exec(q, args...)
+	if err != nil {
+		return 0, err
+	}
+	return res.LastInsertId()
+}
+
+// Tx wraps *sql.Tx with dialect awareness.
+type Tx struct {
+	raw     *sql.Tx
+	dialect Dialect
+}
+
+// Exec executes a query inside the transaction with transparent rewriting.
+func (tx *Tx) Exec(query string, args ...any) (sql.Result, error) {
+	return tx.raw.Exec(rewriteQuery(tx.dialect, query), args...)
+}
+
+// Query executes a query that returns rows inside the transaction.
+func (tx *Tx) Query(query string, args ...any) (*sql.Rows, error) {
+	return tx.raw.Query(rewriteQuery(tx.dialect, query), args...)
+}
+
+// QueryRow executes a query that returns at most one row inside the transaction.
+func (tx *Tx) QueryRow(query string, args ...any) *sql.Row {
+	return tx.raw.QueryRow(rewriteQuery(tx.dialect, query), args...)
+}
+
+// Commit commits the transaction.
+func (tx *Tx) Commit() error { return tx.raw.Commit() }
+
+// Rollback aborts the transaction.
+func (tx *Tx) Rollback() error { return tx.raw.Rollback() }
+
+// ExecReturningID executes an INSERT inside the transaction and returns the id.
+func (tx *Tx) ExecReturningID(query string, args ...any) (int64, error) {
+	q := rewriteQuery(tx.dialect, query)
+	if tx.dialect == DialectPostgres {
+		q = strings.TrimRight(q, "; \t\n") + " RETURNING id"
+		var id int64
+		if err := tx.raw.QueryRow(q, args...).Scan(&id); err != nil {
+			return 0, err
+		}
+		return id, nil
+	}
+	res, err := tx.raw.Exec(q, args...)
+	if err != nil {
+		return 0, err
+	}
+	return res.LastInsertId()
+}
+
+func (db *DB) rewrite(query string) string {
+	return rewriteQuery(db.dialect, query)
+}
+
+func rewriteQuery(dialect Dialect, query string) string {
+	if dialect != DialectPostgres {
+		return query
+	}
+	query = rewriteUserIdentifier(query)
+	query = rewriteInsertOrIgnore(query)
+	query = rewritePlaceholders(query)
+	return query
+}
+
+func rewriteUserIdentifier(query string) string {
+	var buf strings.Builder
+	buf.Grow(len(query) + 16)
+	inSingle := false
+	inDouble := false
+	i := 0
+	for i < len(query) {
+		ch := query[i]
+		if ch == '\'' && !inDouble {
+			if inSingle && i+1 < len(query) && query[i+1] == '\'' {
+				buf.WriteByte(ch)
+				buf.WriteByte(query[i+1])
+				i += 2
+				continue
+			}
+			inSingle = !inSingle
+			buf.WriteByte(ch)
+			i++
+			continue
+		}
+		if ch == '"' && !inSingle {
+			inDouble = !inDouble
+			buf.WriteByte(ch)
+			i++
+			continue
+		}
+		if inSingle || inDouble {
+			buf.WriteByte(ch)
+			i++
+			continue
+		}
+
+		if isIdentifierChar(ch) {
+			j := i + 1
+			for j < len(query) && isIdentifierChar(query[j]) {
+				j++
+			}
+			tok := query[i:j]
+			if strings.EqualFold(tok, "user") {
+				buf.WriteString(`"user"`)
+			} else {
+				buf.WriteString(tok)
+			}
+			i = j
+			continue
+		}
+
+		buf.WriteByte(ch)
+		i++
+	}
+	return buf.String()
+}
+
+func isIdentifierChar(ch byte) bool {
+	if ch >= 'a' && ch <= 'z' {
+		return true
+	}
+	if ch >= 'A' && ch <= 'Z' {
+		return true
+	}
+	if ch >= '0' && ch <= '9' {
+		return true
+	}
+	return ch == '_'
+}
+
+func rewriteInsertOrIgnore(query string) string {
+	upper := strings.ToUpper(query)
+	idx := strings.Index(upper, "INSERT OR IGNORE INTO")
+	if idx < 0 {
+		return query
+	}
+	prefix := query[:idx]
+	suffix := query[idx+len("INSERT OR IGNORE INTO"):]
+	result := prefix + "INSERT INTO" + suffix
+
+	trimmed := strings.TrimRight(result, "; \t\n")
+	return trimmed + " ON CONFLICT DO NOTHING"
+}
+
+func rewritePlaceholders(query string) string {
+	var buf strings.Builder
+	buf.Grow(len(query) + 16)
+	n := 1
+	inString := false
+	for i := 0; i < len(query); i++ {
+		ch := query[i]
+		if ch == '\'' {
+			if inString && i+1 < len(query) && query[i+1] == '\'' {
+				buf.WriteByte(ch)
+				buf.WriteByte(query[i+1])
+				i++
+				continue
+			}
+			inString = !inString
+			buf.WriteByte(ch)
+			continue
+		}
+		if ch == '?' && !inString {
+			buf.WriteString(fmt.Sprintf("$%d", n))
+			n++
+			continue
+		}
+		buf.WriteByte(ch)
+	}
+	return buf.String()
+}