Пример #1
0
// getWhereClause returns a whereClause based on desired upper and lower
// bounds for primary key.
func (qs *QuerySplitter) getWhereClause(whereClause *sqlparser.Where, bindVars map[string]interface{}, start, end sqltypes.Value) *sqlparser.Where {
	var startClause *sqlparser.ComparisonExpr
	var endClause *sqlparser.ComparisonExpr
	var clauses sqlparser.BoolExpr
	// No upper or lower bound, just return the where clause of original query
	if start.IsNull() && end.IsNull() {
		return whereClause
	}
	pk := &sqlparser.ColName{
		Name: sqlparser.SQLName(qs.splitColumn),
	}
	if !start.IsNull() {
		startClause = &sqlparser.ComparisonExpr{
			Operator: sqlparser.GreaterEqualStr,
			Left:     pk,
			Right:    sqlparser.ValArg([]byte(":" + startBindVarName)),
		}
		bindVars[startBindVarName] = start.ToNative()
	}
	// splitColumn < end
	if !end.IsNull() {
		endClause = &sqlparser.ComparisonExpr{
			Operator: sqlparser.LessThanStr,
			Left:     pk,
			Right:    sqlparser.ValArg([]byte(":" + endBindVarName)),
		}
		bindVars[endBindVarName] = end.ToNative()
	}
	if startClause == nil {
		clauses = endClause
	} else {
		if endClause == nil {
			clauses = startClause
		} else {
			// splitColumn >= start AND splitColumn < end
			clauses = &sqlparser.AndExpr{
				Left:  startClause,
				Right: endClause,
			}
		}
	}
	if whereClause != nil {
		clauses = &sqlparser.AndExpr{
			Left:  &sqlparser.ParenBoolExpr{Expr: whereClause.Expr},
			Right: &sqlparser.ParenBoolExpr{Expr: clauses},
		}
	}
	return &sqlparser.Where{
		Type: sqlparser.WhereStr,
		Expr: clauses,
	}
}