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Add datalog infrastructure for min aggregation function

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This patch adds an instruction to the datalog interpreter and
constructs a new AST node for min aggregation functions.

The compiler is currently still work in progress and depends on
changes made to the handling of simple joins and the preprocessor.

Signed-off-by: Alex Horn <t-alexh@microsoft.com>
This commit is contained in:
Alex Horn 2015-06-10 18:09:56 +01:00
parent 004bf1471f
commit 140fb7942d
11 changed files with 418 additions and 3 deletions
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28
src/muz/rel/dl_base.h
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@ -192,6 +192,29 @@ namespace datalog {
virtual base_object * operator()(const base_object & t1, const base_object & t2) = 0;
};
/**
\brief Aggregate minimum value
Informally, we want to group rows in a table \c t by \c group_by_cols and
return the minimum value in column \c col among each group.
Let \c t be a table with N columns.
Let \c group_by_cols be a set of column identifers for table \c t such that |group_by_cols| < N.
Let \c col be a column identifier for table \c t such that \c col is not in \c group_by_cols.
Let R_col be a set of rows in table \c t such that, for all rows r_i, r_j in R_col
and column identifiers k in \c group_by_cols, r_i[k] = r_j[k].
For each R_col, we want to restrict R_col to those rows whose value in column \c col is minimal.
min_fn(R, group_by_cols, col) =
{ row in R | forall row' in R . row'[group_by_cols] = row[group_by_cols] => row'[col] >= row[col] }
*/
class min_fn : public base_fn {
public:
virtual base_object * operator()(const base_object & t) = 0;
};
class transformer_fn : public base_fn {
public:
virtual base_object * operator()(const base_object & t) = 0;
@ -856,6 +879,7 @@ namespace datalog {
typedef table_infrastructure::base_fn base_table_fn;
typedef table_infrastructure::join_fn table_join_fn;
typedef table_infrastructure::min_fn table_min_fn;
typedef table_infrastructure::transformer_fn table_transformer_fn;
typedef table_infrastructure::union_fn table_union_fn;
typedef table_infrastructure::mutator_fn table_mutator_fn;
@ -1020,6 +1044,7 @@ namespace datalog {
class table_plugin : public table_infrastructure::plugin_object {
friend class relation_manager;
class min_fn;
protected:
table_plugin(symbol const& n, relation_manager & manager) : plugin_object(n, manager) {}
public:
@ -1027,6 +1052,9 @@ namespace datalog {
virtual bool can_handle_signature(const table_signature & s) { return s.functional_columns()==0; }
protected:
virtual table_min_fn * mk_min_fn(const table_base & t,
unsigned_vector & group_by_cols, const unsigned col);
/**
If the returned value is non-zero, the returned object must take ownership of \c mapper.
Otherwise \c mapper must remain unmodified.