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Add a test showing our behavior when migrating from an optional column to a required column. 

Optional values are not automatically migrated to required columns since it is a lossy process.

This test case revealed an issue where the number of objects can be lost if all properties of an
object were optional and are all being migrated to required. This happens because the migration
process removes the optional columns in a first pass, and recreates them as required in a second
pass. Since this results in all columns being removed, we lose track of how many objects were
stored. We avoid this by detecting the case where we are about to remove the last column and
inserting a placeholder column that we'll remove after inserting the new columns.
This commit is contained in:
Mark Rowe 2015-10-19 18:53:09 -07:00 committed by Mark Rowe
parent 9f1702a10f
commit 0b45772a0b
1 changed files with 18 additions and 0 deletions
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18
object_store.cpp
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@ -293,6 +293,8 @@ bool ObjectStore::create_tables(Group *group, Schema &target_schema, bool update
changed = true;
}
bool inserted_placeholder_column = false;
// remove extra columns
size_t deleted = 0;
for (auto& current_prop : current_schema.properties) {
@ -301,6 +303,13 @@ bool ObjectStore::create_tables(Group *group, Schema &target_schema, bool update
auto target_prop = target_object_schema->property_for_name(current_prop.name);
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;
@ -336,6 +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