docs: void setColNullability(ColumnSchema column, boolean nullable) {
  
          Constraint c        = null;
          int        colIndex = table.getColumnIndex(column.getName().name);
  
          if (column.isNullable() == nullable) {
              return;
          }
  
          if (nullable) {
              if (column.isPrimaryKey()) {
                  throw Error.error(ErrorCode.X_42526);
              }
  
              table.checkColumnInFKConstraint(colIndex, Constraint.SET_NULL);
              removeColumnNotNullConstraints(colIndex);
          } else {
              HsqlName constName = database.nameManager.newAutoName("CT",
                  table.getSchemaName(), table.getName(),
                  SchemaObject.CONSTRAINT);
  
              c       = new Constraint(constName, true, null, Constraint.CHECK);
              c.check = new ExpressionLogical(column);
  
              c.prepareCheckConstraint(session, table, true);
              column.setNullable(false);
              table.addConstraint(c);
              table.setColumnTypeVars(colIndex);
              database.schemaManager.addSchemaObject(c);
          }
      }