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Refs Tokutek/ft-index#46 documentation/comments

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Yoni Fogel 2014-01-29 20:59:15 -08:00
parent 12937dc284
commit eef0ab7812
2 changed files with 25 additions and 4 deletions
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1
util/dmt.cc
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@ -225,6 +225,7 @@ int dmt<dmtdata_t, dmtdataout_t>::insert_at(const dmtdatain_t &value, const uint
paranoid_invariant(!is_array);
if (!same_size) {
this->values_same_size = false;
this->value_length = 0;
}
this->maybe_resize_tree(&value);

28
util/dmt.h
View file

@ -181,7 +181,7 @@ public:
paranoid_invariant(index != NODE_NULL);
m_index = index;
}
} __attribute__((__packed__,aligned(4)));
} __attribute__((__packed__,__aligned__(4)));
template<typename dmtdata_t>
class dmt_node_templated {
@ -191,7 +191,7 @@ public:
subtree right;
uint32_t value_length;
dmtdata_t value;
} __attribute__((__packed__,aligned(4)));
} __attribute__((__aligned__(4))); //NOTE: we cannot use attribute packed or dmtdata_t will call copy constructors (dmtdata_t might not be packed by default)
}
@ -517,9 +517,29 @@ private:
subtree root;
};
// TODO(yoni): comment relationship between values_same_size, num values, value_length, note about tree still keeping track (until lost once)
/*
Relationship between values_same_size, d.a.num_values, value_length, is_array:
In an empty dmt:
is_array is true
value_same_size is true
value_length is undefined
d.a.num_values is 0
In a non-empty array dmt:
is_array is true
values_same_size is true
value_length is defined
d.a.num_values > 0
In a non-empty tree dmt:
is_array = false
value_same_size is true iff all values have been the same size since the last time the dmt turned into a tree.
value_length is defined iff values_same_size is true
d.a.num_values is undefined (the memory is used for the tree)
Note that in tree form, the dmt keeps track of if all values are the same size until the first time they are not.
'values_same_size' will not become true again (even if we change all values to be the same size)
until/unless the dmt becomes empty, at which point it becomes an array again.
*/
bool values_same_size;
uint32_t value_length;
uint32_t value_length; // valid iff values_same_size is true.
struct mempool mp;
bool is_array;
union {