fix: EXPLAIN <query> actions either disabled or non-working for PostgreSQL and SQLite

Refs #2540

Author: ansgarbecker

source/dbstructures.postgresql.pas

@@ -726,6 +726,7 @@ function TPostgreSQLProvider.GetSql(AId: TQueryId): string;
       ' WHERE pg_class.relkind=''r'''+
       '   AND pg_namespace.nspname=:EscapedDatabase'+
       '   AND pg_class.relname=:EscapedName';
+    qExplain: Result := 'EXPLAIN %s';
     qGetEnumTypes: Result := IfThen(
       FServerVersion >= 90000,
       'SELECT ' +

source/dbstructures.sqlite.pas

@@ -427,6 +427,7 @@ function TSQLiteProvider.GetSql(AId: TQueryId): string;
     qGetCharsets: Result := 'SELECT ''UTF-8'' AS "Charset", ''UTF-8'' AS "Description" '+
       'UNION SELECT ''UTF-16le'', ''UTF-16 Little Endian'' '+
       'UNION SELECT ''UTF-16be'', ''UTF-16 Big Endian''';
+    qExplain: Result := 'EXPLAIN %s';
     qCastAsText: Result := 'CAST(%s AS CHAR)';
     else Result := inherited;
   end;

source/main.pas

@@ -6736,7 +6736,7 @@ procedure TMainForm.ValidateQueryControls(Sender: TObject);
   actExecuteQuery.Enabled := HasConnection and InQueryTab and NotEmpty and (not Tab.QueryRunning);
   actExecuteSelection.Enabled := HasConnection and InQueryTab and HasSelection and (not Tab.QueryRunning);
   actExecuteCurrentQuery.Enabled := actExecuteQuery.Enabled;
-  actExplainCurrentQuery.Enabled := actExecuteQuery.Enabled and (Conn.Parameters.NetTypeGroup in [ngMySQL, ngPgSQL, ngSQLite]);
+  actExplainCurrentQuery.Enabled := actExecuteQuery.Enabled and Conn.SqlProvider.Has(qExplain);
   actSaveSQLAs.Enabled := InQueryTab and NotEmpty;
   actSaveSQL.Enabled := (actSaveSQLAs.Enabled and Tab.Memo.Modified) or InEditorTab;
   actSaveSQLselection.Enabled := InQueryTab and HasSelection;
@@ -9303,7 +9303,7 @@ procedure TMainForm.ListProcessesFocusChanged(Sender: TBaseVirtualTree;
 
   SynMemoProcessView.Enabled := EnableControls;
   pnlProcessView.Enabled := EnableControls;
-  lblExplainProcess.Enabled := EnableControls and ActiveConnection.Parameters.IsAnyMySQL;
+  lblExplainProcess.Enabled := EnableControls and ActiveConnection.SqlProvider.Has(qExplain);
   menuExplainProcess.Enabled := lblExplainProcess.Enabled;
 end;