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Merge pull request #8 from realm/mar-migrate-required-to-optional 

Support migrating required columns to optional, preserving their contents
This commit is contained in:
Mark Rowe 2015-10-21 14:40:44 -07:00
parent f5b790cf87 0b45772a0b
commit 347145b4f1
1 changed files with 83 additions and 1 deletions
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84
object_store.cpp
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@ -149,6 +149,13 @@ static inline bool property_has_changed(Property const& p1, Property const& p2)
|| p1.is_nullable != p2.is_nullable;
}
static inline bool property_can_be_migrated_to_nullable(const Property& old_property, const Property& new_property) {
return old_property.type == new_property.type
&& !old_property.is_nullable
&& new_property.is_nullable
&& new_property.name == old_property.name;
}
void ObjectStore::verify_schema(Schema const& actual_schema, Schema& target_schema, bool allow_missing_tables) {
std::vector<ObjectSchemaValidationException> errors;
for (auto &object_schema : target_schema) {
@ -205,6 +212,45 @@ std::vector<ObjectSchemaValidationException> ObjectStore::verify_object_schema(O
return exceptions;
}
template <typename T>
static void copy_property_values(const Property& old_property, const Property& new_property, Table& table,
T (Table::*getter)(std::size_t, std::size_t) const noexcept,
void (Table::*setter)(std::size_t, std::size_t, T)) {
size_t old_column = old_property.table_column, new_column = new_property.table_column;
size_t count = table.size();
for (size_t i = 0; i < count; i++) {
(table.*setter)(new_column, i, (table.*getter)(old_column, i));
}
}
static void copy_property_values(const Property& source, const Property& destination, Table& table) {
switch (destination.type) {
case PropertyTypeInt:
copy_property_values(source, destination, table, &Table::get_int, &Table::set_int);
break;
case PropertyTypeBool:
copy_property_values(source, destination, table, &Table::get_bool, &Table::set_bool);
break;
case PropertyTypeFloat:
copy_property_values(source, destination, table, &Table::get_float, &Table::set_float);
break;
case PropertyTypeDouble:
copy_property_values(source, destination, table, &Table::get_double, &Table::set_double);
break;
case PropertyTypeString:
copy_property_values(source, destination, table, &Table::get_string, &Table::set_string);
break;
case PropertyTypeData:
copy_property_values(source, destination, table, &Table::get_binary, &Table::set_binary);
break;
case PropertyTypeDate:
copy_property_values(source, destination, table, &Table::get_datetime, &Table::set_datetime);
break;
default:
break;
}
}
// set references to tables on targetSchema and create/update any missing or out-of-date tables
// if update existing is true, updates existing tables, otherwise validates existing tables
// NOTE: must be called from within write transaction
@ -230,13 +276,40 @@ bool ObjectStore::create_tables(Group *group, Schema &target_schema, bool update
ObjectSchema current_schema(group, target_object_schema->name);
std::vector<Property> &target_props = target_object_schema->properties;
// handle columns changing from required to optional
for (auto& current_prop : current_schema.properties) {
auto target_prop = target_object_schema->property_for_name(current_prop.name);
if (!target_prop || !property_can_be_migrated_to_nullable(current_prop, *target_prop))
continue;
target_prop->table_column = current_prop.table_column;
current_prop.table_column = current_prop.table_column + 1;
table->insert_column(target_prop->table_column, DataType(target_prop->type), target_prop->name, target_prop->is_nullable);
copy_property_values(current_prop, *target_prop, *table);
table->remove_column(current_prop.table_column);
current_prop.table_column = target_prop->table_column;
changed = true;
}
bool inserted_placeholder_column = false;
// remove extra columns
size_t deleted = 0;
for (auto& current_prop : current_schema.properties) {
current_prop.table_column -= deleted;
auto target_prop = target_object_schema->property_for_name(current_prop.name);
if (!target_prop || property_has_changed(current_prop, *target_prop)) {
if (!target_prop || (property_has_changed(current_prop, *target_prop)
&& !property_can_be_migrated_to_nullable(current_prop, *target_prop))) {
if (deleted == current_schema.properties.size() - 1) {
// We're about to remove the last column from the table. Insert a placeholder column to preserve
// the number of rows in the table for the addition of new columns below.
table->add_column(type_Bool, "placeholder");
inserted_placeholder_column = true;
}
table->remove_column(current_prop.table_column);
++deleted;
current_prop.table_column = npos;
@ -272,6 +345,15 @@ bool ObjectStore::create_tables(Group *group, Schema &target_schema, bool update
}
}
if (inserted_placeholder_column) {
// We inserted a placeholder due to removing all columns from the table. Remove it, and update the indices
// of any columns that we inserted after it.
table->remove_column(0);
for (auto& target_prop : target_props) {
target_prop.table_column--;
}
}
// update table metadata
if (target_object_schema->primary_key.length()) {
// if there is a primary key set, check if it is the same as the old key