fix(pgsql): do not pass schema to SlaveLink in Tables() and TableFields()

In PostgreSQL, schema is a namespace within the database, not a separate
database. Passing schema to SlaveLink() attempts to connect to a different
database with that name, which fails.

For proper PostgreSQL schema support:
- Tables(ctx, schema): schema parameter is used in SQL query to filter tables
- TableFields(ctx, "schema.table"): table can be schema-qualified in regclass

Removed unused gutil import from pgsql_table_fields.go.

Author: lingcoder

contrib/drivers/pgsql/pgsql_table_fields.go

@@ -11,7 +11,6 @@ import (
 	"fmt"
 
 	"github.com/gogf/gf/v2/database/gdb"
-	"github.com/gogf/gf/v2/util/gutil"
 )
 
 var (
@@ -49,13 +48,14 @@ func init() {
 // TableFields retrieves and returns the fields' information of specified table of current schema.
 func (d *Driver) TableFields(ctx context.Context, table string, schema ...string) (fields map[string]*gdb.TableField, err error) {
 	var (
-		result     gdb.Result
-		link       gdb.Link
-		usedSchema = gutil.GetOrDefaultStr(d.GetSchema(), schema...)
-		// TODO duplicated `id` result?
+		result gdb.Result
+		link   gdb.Link
+		// In PostgreSQL, schema is a namespace within the database.
+		// The table parameter can be schema-qualified (e.g., "myschema.mytable").
+		// DO NOT pass schema to SlaveLink - it would attempt to connect to a different database.
 		structureSql = fmt.Sprintf(tableFieldsSqlTmp, table)
 	)
-	if link, err = d.SlaveLink(usedSchema); err != nil {
+	if link, err = d.SlaveLink(); err != nil {
 		return nil, err
 	}
 	result, err = d.DoSelect(ctx, link, structureSql)

contrib/drivers/pgsql/pgsql_tables.go

@@ -70,8 +70,10 @@ func (d *Driver) Tables(ctx context.Context, schema ...string) (tables []string,
 		result     gdb.Result
 		usedSchema = gutil.GetOrDefaultStr(d.GetConfig().Namespace, schema...)
 	)
-	// DO NOT use `usedSchema` as parameter for function `SlaveLink`.
-	link, err := d.SlaveLink(schema...)
+	// DO NOT pass schema to SlaveLink - in PostgreSQL, schema is a namespace within
+	// the database, not the database itself. Passing schema to SlaveLink would attempt
+	// to connect to a different database named "schema", which is incorrect.
+	link, err := d.SlaveLink()
 	if err != nil {
 		return nil, err
 	}