#include <tupleitem.h>
/**
- * A relation is an implementation of a tuple set with a primary key
- * through a hashvector whose "type" defines the key. Additional
- * hashvectors may be added to impose additional key restrictions and
- * the final relation is the intersection of them all.
- *
- * The relation record itself holds the column schema whereas the
- * indexes hold key schemas that in practice are copies of the column
- * schema with some columns blanked out.
+ * A relation is an implementation of a tuple set with (optional) key
+ * constraints. The store is a \ref hashvector whose \b type is a \ref
+ * tupleschema that defines the columns. The key constraints are
+ * represented as additional \ref hashvector "hashvectors" whose \ref
+ * tupleschema "tupleschemas" are clones of the column schema with
+ * some columns excluded.
+ *
+ * \extends hashvector
*/
typedef struct {
- vector indexes; // one or more indexes over the tuple collection
- tupleschema *columns;
+ /**
+ * This is the primary content store for the relation. Its type
+ * should be a tupleschema declaring the "item types" for the
+ * relation columns.
+ */
+ hashvector content;
+
+ /**
+ * This is a collection of relational constraints, if any, which
+ * are represented as hashvectors whose tupleschemas are clones of
+ * the content tupleschema with some columns excluded.
+ */
+ vector constraints;
} relation;
/**
- * Create a relation of the given arity and tupleschema.
+ * \brief Create a relation for the given tupleschema.
+ *
+ * \param schema is the column schema
+ *
+ * \returns the allocated relation record.
+ *
+ * The given tupleschema is set up as the type of the content
+ * hashvector, which also is initialised as a nibble_index_levels
+ * variant vector.
+ *
+ * \related relation
*/
-extern relation *relation_create(int arity,tupleschema *schema);
+extern relation *relation_create(tupleschema *schema);
/**
- * Add a a key index to the relation by identifying the value part for
- * this index.
+ * \brief Add a key constraint to a \ref relation.
+ *
+ * \param r is the relation concerned.
+ *
+ * \param key is the constraint \ref tupleschema.
+ *
+ * \returns the index into the constraints \ref vector for the added
+ * constraint.
+ *
+ * This function adds a \ref hashvector with the provided \ref
+ * tupleschema as its item type. The \b key \ref tupleschema must be a
+ * clone of the \ref relation column schema with some (or all) value
+ * columns marked as \b 0. Such a \ref tupleschema may be obtained via
+ * the function \ref tupleschema_mask to clone the \ref relation
+ * content type (casted as \ref tupleschema*) and clear columns by
+ * their index.
+ *
+ * The constraint \ref hashvectors are used when tuples are added to
+ * the \ref relation so as to identify the already contained tuples
+ * that contradict the addition by means of having the same constraint
+ * key. The already contained tuples are then "knocked out" from the
+ * relation by the new addition.
+ *
+ * \see tupleschema_mask, relation_add
+ * \related relation
*/
-extern int relation_addindex(relation *r,tupleschema *ts);
-
+extern int relation_add_contraint(relation *r,tupleschema *key);
/**
- * Add a tuple to a relation.
+ * \brief Add the tuple to the relation.
+ *
+ * \param r is the \ref relation concerned.
+ *
+ * \param t is the \ref tuple to add.
+ *
* \returns a vector of all knocked out tuples.
+ *
+ * This function adds the \ref tuple \b t to the \ref relation \b r,
+ * and it returns a \ref vector (single_index_level variant) of all
+ * same-key constraint tuples. The returned vector is malloc-ed and it
+ * must be free-ed by the caller. If the tuple is already contained or
+ * there are no other same-key tuples knocked out, then \b 0 is
+ * returned.
+ *
+ * \related relation
*/
extern vector *relation_add(relation *r,tuple *t);
+/**
+ * \brief Delete all tuples matching to the query \ref tuple fromt the
+ * \ref relation.
+ *
+ * \param r is the \ref relation concerned.
+ *
+ * \param t is the \ref tuple to delete.
+ *
+ * \returns a \vector vector of all knocked out tuples, i.e. the
+ * same-key tuples, if any, contained in the relation
+ *
+ * Note that deletion uses a "query" tuple, which means that some
+ * columns may be null to mark that them match to any value.
+ *
+ * \related relation
+ */
+extern vector *relation_delete(relation *r,tuple *query);
+
+/**
+ * \brief Return the next \ref tuple in the \ref relation that matches
+ * to the query \ref tuple, at or after the index.
+ *
+ * \param r is the \ref relation concerned.
+ *
+ * \param index is a pointer to the \ref vector index to update.
+ *
+ * \param query is a query \tuple tuple for selection of certain
+ * column values.
+ *
+ * \returns any such matching \tuple tuple and an updateed *index.
+ *
+ * \related relation
+ */
+extern void *relation_next(relation *r,vector_index *index,tuple *query);
+
#endif
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