diff options
Diffstat (limited to 'src/operations.erl')
| -rw-r--r-- | src/operations.erl | 593 |
1 files changed, 152 insertions, 441 deletions
diff --git a/src/operations.erl b/src/operations.erl index 4a492f4..e224800 100644 --- a/src/operations.erl +++ b/src/operations.erl @@ -38,25 +38,24 @@ %%% @reference E. F. Codd (1970). "A Relational Model of Data for Large Shared Data Banks" -module(operations). --include("operations.hrl"). --export([setup/0, - hash/1, - create_database/1, +-include("../include/operations.hrl"). +-export([ + create_database/1, create_relation/3, create_immutable_relation/2, create_tuple/3, + create_all_tuples/3, retract_tuple/3, retract_tuple/4, clear_relation/2, clear_relation/3, retract_relation/2, retract_relation/3, - get_relations/1, - get_relation_hash/2, - hashes_from_tuple/1, - get_tuples_iterator/2, - get_tuples_iterator/3, - take/3, + get_relation_hash/2, + get_relations/1, + hashes_from_tuple/1, + get_tuples_iterator/2, + get_iterator_from_generator/2, next_tuple/1, close_iterator/1, collect_all/1, @@ -69,48 +68,10 @@ equijoin_iterator/3, theta_join_iterator/3, %% Materialization (eager) - materialize/3]). - -%% @doc Initialize Mnesia database schema and tables. -%% -%% Creates a fresh Mnesia schema with four tables for content-addressed storage: -%% <ul> -%% <li>`attribute' - Hash → Value mapping for deduplication</li> -%% <li>`tuple' - Hash → Tuple mapping with attribute references</li> -%% <li>`relation' - Hash → Relation with merkle tree and schema</li> -%% <li>`database_state' - Hash → Database with relation merkle tree</li> -%% </ul> -%% -%% <b>Warning:</b> This function deletes any existing schema and recreates it from scratch. -%% -%% @returns `ok' on success -%% @see create_database/1 -setup() -> - mnesia:stop(), - mnesia:delete_schema([node()]), - mnesia:create_schema([node()]), - mnesia:start(), - mnesia:create_table(attribute, [ - {attributes, [hash, value]}, - {disc_copies, [node()]}, - {type, set} - ]), - mnesia:create_table(tuple, [ - {attributes, [hash, relation, attribute_map]}, - {disc_copies, [node()]}, - {type, set} - ]), - mnesia:create_table(relation, [ - {attributes, [hash, name, tree, schema, constraints, cardinality, generator, membership_criteria, mutability, provenance]}, - {disc_copies, [node()]}, - {type, set} - ]), - mnesia:create_table(database_state, [ - {attributes, [hash, name, tree, relations, timestamp]}, - {disc_copies, [node()]}, - {type, set} - ]). + materialize/3 +]). +%% @private %% @doc Compute SHA-256 hash of an Erlang term. %% %% This is the foundational hashing function used throughout the system for @@ -157,18 +118,10 @@ create_tuple(Database, RelationName, Tuple) when is_map(Tuple), is_record(Databa %% Check if relation is immutable before attempting insert CurrentRelationHash = maps:get(RelationName, Database#database_state.relations), [RelationRecord] = mnesia:dirty_read(relation, CurrentRelationHash), + create_tuple_internal(Database, RelationName, Tuple, RelationRecord). - case RelationRecord#relation.mutability of - immutable -> - {error, {immutable_relation, RelationName}}; - mutable -> - create_tuple_internal(Database, RelationName, Tuple, RelationRecord); - undefined -> - %% Backwards compatibility: treat undefined as mutable - create_tuple_internal(Database, RelationName, Tuple, RelationRecord) - end. - -%% Internal function for tuple creation (after mutability check) +%% @private +%% Internal function for tuple creation create_tuple_internal(Database, RelationName, Tuple, _RelationRecord) -> F = fun() -> %% Step 1: Store each attribute value and build attribute_map @@ -212,8 +165,13 @@ create_tuple_internal(Database, RelationName, Tuple, _RelationRecord) -> constraints = RelationRecord#relation.constraints, cardinality = NewCardinality, generator = RelationRecord#relation.generator, - provenance = RelationRecord#relation.provenance + provenance = RelationRecord#relation.provenance, + lineage = RelationRecord#relation.lineage, + membership_criteria = RelationRecord#relation.membership_criteria }, + %% Delete old relation record before writing new one + %% This ensures only one relation record exists per name + mnesia:delete({relation, CurrentRelationHash}), mnesia:write(relation, UpdatedRelation, write), %% Step 7: Update database relations map @@ -423,6 +381,20 @@ create_relation(Database, Name, Definition) when is_record(Database, database_st %% Two relations might share definitions but their name gives another interpretation %% and therefore different tuples RelationHash = hash({Name, Definition, undefined}), + + %% Returns a generator function (not a PID) that yields tuples one at a time + %% TODO: investigate if a generator should or should not be bound to a specific DATABASE VERSION. If so, create the fun passing the DB as an attribute + GeneratorFun = fun() -> + [CurrentRelation] = mnesia:dirty_index_read(relation, Name, #relation.name), + CurrentHash = CurrentRelation#relation.hash, + TupleHashes = case CurrentRelation#relation.tree of + undefined -> []; + _ -> hashes_from_tuple(CurrentHash) + end, + InnerGen = make_finite_generator(TupleHashes), + spawn(fun() -> generator_iterator_loop(InnerGen) end) + end, + NewRelation = #relation{ hash = RelationHash, name = Name, @@ -430,10 +402,10 @@ create_relation(Database, Name, Definition) when is_record(Database, database_st schema = Definition, constraints = #{}, % No constraints by default cardinality = {finite, 0}, % Empty relation - generator = undefined, % Finite relation has no generator + generator = GeneratorFun, % Function generator for finite relations membership_criteria = #{}, % No membership criteria by default - mutability = mutable, % Mutable by default - provenance = {base, Name} % Base relation + provenance = build_base_provenance(Definition, Name), % Base relation provenance + lineage = {base, Name} % Base relation lineage }, mnesia:write(relation, NewRelation, write), @@ -494,42 +466,42 @@ create_database(Name) -> %% Standard immutable relations (domains and their predicates) StandardTypeRelations = [ %% Boolean domain - finite, immutable - #immutable_relation_spec{ + #domain{ name = boolean, schema = #{value => boolean}, - generator = {generators, boolean}, + generator = fun() -> spawn(fun() -> generator_iterator_loop(generators:boolean(#{})) end) end, membership_criteria = #{value => {in, [true, false]}}, cardinality = {finite, 2} }, %% Natural numbers - infinite, immutable - #immutable_relation_spec{ + #domain{ name = natural, schema = #{value => natural}, - generator = {generators, natural}, + generator = fun() -> spawn(fun() -> generator_iterator_loop(generators:natural(#{})) end) end, membership_criteria = #{value => {'and', {gte, 0}, is_integer}}, cardinality = aleph_zero }, %% Integers - infinite, immutable - #immutable_relation_spec{ + #domain{ name = integer, schema = #{value => integer}, - generator = {generators, integer}, + generator = fun() -> spawn(fun() -> generator_iterator_loop(generators:integer(#{})) end) end, membership_criteria = #{value => is_integer}, cardinality = aleph_zero }, %% Rationals - infinite, immutable - #immutable_relation_spec{ + #domain{ name = rational, schema = #{numerator => integer, denominator => integer}, - generator = {generators, rational}, + generator = fun() -> spawn(fun() -> generator_iterator_loop(generators:rational(#{})) end) end, membership_criteria = #{denominator => {neq, 0}}, cardinality = aleph_zero } %% Reals - TODO: implement - %% #immutable_relation_spec{ + %% #domain{ %% name = reals, %% schema = #{value => reals}, - %% generator = {generators, reals}, + %% generator = fun() -> spawn(fun() -> generator_iterator_loop(generators:reals(#{})) end) end, %% membership_criteria = #{value => is_float}, %% cardinality = continuum %% } @@ -561,7 +533,7 @@ create_database(Name) -> %% == Example == %% <pre> %% %% Create immutable relation of natural numbers -%% {DB1, Naturals} = operations:create_immutable_relation(DB, #immutable_relation_spec{ +%% {DB1, Naturals} = operations:create_immutable_relation(DB, #domain{ %% name = naturals, %% schema = #{value => naturals}, %% generator = {generators, naturals}, @@ -575,19 +547,19 @@ create_database(Name) -> %% </pre> %% %% @param Database `#database_state{}' record -%% @param Specification `#immutable_relation_spec{}' record +%% @param Specification `#domain{}' record %% @returns `{UpdatedDatabase, NewRelation}' %% %% @see create_relation/3 %% @see get_tuples_iterator/3 create_immutable_relation(Database, Specification) when is_record(Database, database_state) - andalso is_record(Specification, immutable_relation_spec) -> - Name = Specification#immutable_relation_spec.name, - Schema = Specification#immutable_relation_spec.schema, - Generator = Specification#immutable_relation_spec.generator, - MembershipCriteria = Specification#immutable_relation_spec.membership_criteria, - Cardinality = Specification#immutable_relation_spec.cardinality, + andalso is_record(Specification, domain) -> + Name = Specification#domain.name, + Schema = Specification#domain.schema, + Generator = Specification#domain.generator, + MembershipCriteria = Specification#domain.membership_criteria, + Cardinality = Specification#domain.cardinality, F = fun() -> RelationHash = hash({Name, Schema, undefined}), @@ -601,8 +573,8 @@ create_immutable_relation(Database, Specification) cardinality = Cardinality, generator = Generator, membership_criteria = MembershipCriteria, - mutability = immutable, % Always immutable - provenance = {base, Name} + provenance = build_base_provenance(Schema, Name), % Base relation provenance + lineage = {base, Name} % Base relation lineage }, mnesia:write(relation, NewRelation, write), @@ -627,19 +599,6 @@ create_immutable_relation(Database, Specification) {atomic, Result} = mnesia:transaction(F), Result. -%% @doc Get all relation names in a database. -%% -%% Returns a list of atoms representing all relation names currently -%% defined in the database. -%% -%% @param Database `#database_state{}' record -%% @returns List of atoms (relation names) -%% -%% @see get_relation_hash/2 -%% @see create_relation/3 -get_relations(Database) -> - maps:keys(Database#database_state.relations). - %% @doc Get relation hash by name. %% %% Looks up a relation's hash in the database's relation map. This hash @@ -657,6 +616,17 @@ get_relation_hash(Database, RelationName) -> X -> X end. +%% @doc Get list of all relation names in the database. +%% +%% Returns a list of all relation names (atoms) currently stored in the database. +%% This includes both user-defined relations and built-in infinite relations. +%% +%% @param Database `#database_state{}' record +%% @returns List of relation names (atoms) +-spec get_relations(#database_state{}) -> [atom()]. +get_relations(Database) -> + maps:keys(Database#database_state.relations). + %% @doc Resolve a tuple hash to actual values. %% %% This is an internal function that materializes a tuple by: @@ -699,75 +669,6 @@ hashes_from_tuple(RelationHash) -> Tree -> merklet:keys(Tree) end. -%% @doc Take operator (τ): Returns N arbitrary elements from a relation. -%% -%% The take operator is a unary relational operator that produces a finite -%% relation containing N arbitrary elements from the input relation. Since -%% relations are sets (unordered), the specific elements returned are -%% determined by the enumeration order. -%% -%% For finite relations smaller than N, returns all elements. -%% For infinite relations, returns first N elements by generator order. -%% -%% == Example == -%% <pre> -%% %% Take 100 naturals (returns {0, 1, 2, ..., 99}) -%% {DB1, Naturals100} = operations:take(DB, naturals, 100). -%% -%% %% Can compose with other operators -%% Iterator = operations:get_tuples_iterator(DB1, naturals100). -%% </pre> -%% -%% @param Database `#database_state{}' record -%% @param RelationName Atom naming the source relation -%% @param N Number of elements to take -%% @returns `{UpdatedDatabase, TakeRelation}' where TakeRelation is finite -%% -%% @see get_tuples_iterator/3 -take(Database, RelationName, N) when is_record(Database, database_state), is_integer(N), N > 0 -> - case maps:get(RelationName, Database#database_state.relations, error) of - error -> - erlang:error({relation_not_found, RelationName}); - RelationHash -> - [SourceRelation] = mnesia:dirty_read(relation, RelationHash), - - %% Compute cardinality of result - ResultCardinality = case SourceRelation#relation.cardinality of - {finite, M} when M < N -> {finite, M}; - {finite, _} -> {finite, N}; - _ -> {finite, N} % Taking from infinite yields finite - end, - - %% Create take relation - TakeName = list_to_atom(atom_to_list(RelationName) ++ "_take_" ++ integer_to_list(N)), - - TakeHash = hash({take, RelationName, N}), - - TakeRelation = #relation{ - hash = TakeHash, - name = TakeName, - tree = undefined, % Generated on-demand - schema = SourceRelation#relation.schema, - constraints = SourceRelation#relation.constraints, - cardinality = ResultCardinality, - generator = {take, RelationName, N}, - membership_criteria = #{}, - mutability = immutable, % Take relations are read-only - provenance = {take, SourceRelation#relation.provenance, N} - }, - - %% Register the take relation (ephemeral - not persisted to Mnesia disk) - %% This allows get_tuples_iterator to find it - UpdatedDatabase = Database#database_state{ - relations = maps:put(TakeName, TakeHash, Database#database_state.relations) - }, - - %% Store in Mnesia (in-memory transaction) - mnesia:dirty_write(relation, TakeRelation), - - {UpdatedDatabase, TakeRelation} - end. - %% @doc Create an iterator for streaming tuples from a relation with constraints. %% %% Extended version of get_tuples_iterator/2 that accepts boundedness constraints. @@ -818,83 +719,32 @@ take(Database, RelationName, N) when is_record(Database, database_state), is_int %% %% @param Database `#database_state{}' record %% @param RelationName Atom naming the relation to iterate -%% @param Options Map of constraints (nested or flat format) %% @returns Pid of iterator process %% %% @see get_tuples_iterator/2 %% @see take/3 -get_tuples_iterator(Database, RelationName, Options) when is_record(Database, database_state) -> +get_tuples_iterator(Database, RelationName) when is_record(Database, database_state) -> case maps:get(RelationName, Database#database_state.relations, error) of error -> - erlang:error({error_tuple_iterator_init, RelationName}); + erlang:error({error_tuple_iterator_init, relation_not_found, RelationName}); RelationHash -> [Relation] = mnesia:dirty_read(relation, RelationHash), - - %% Extract constraints from options (support both nested and flat format) - Constraints = case maps:is_key(constraints, Options) of - true -> maps:get(constraints, Options); - false -> Options %% Flat format: entire map is constraints - end, - - %% Metadata tracking is ALWAYS enabled case Relation#relation.cardinality of {finite, _} when Relation#relation.tree =/= undefined -> - %% Finite relation with materialized tuples: use tuple hashes TupleHashes = hashes_from_tuple(RelationHash), - spawn(fun() -> tuple_iterator_loop(TupleHashes, RelationName, true) end); - + spawn(fun() -> tuple_iterator_loop(TupleHashes) end); _ -> - %% Relation with generator (infinite or take) or empty finite relation - case Relation#relation.generator of - undefined -> - %% Empty finite relation without materialized tuples - spawn(fun() -> tuple_iterator_loop([], RelationName, true) end); - - {take, SourceRelName, N} -> - %% Take relation: get source iterator and limit to N tuples - SourceIter = get_tuples_iterator(Database, SourceRelName, Constraints), - spawn(fun() -> take_iter_loop(SourceIter, N, 0, N) end); - - {GeneratorModule, GeneratorFunction} -> - %% Normal generator (naturals, integers, etc.) - Generator = erlang:apply(GeneratorModule, GeneratorFunction, [Constraints]), - spawn(fun() -> generator_iterator_loop(Generator, RelationName, true) end) - end + get_iterator_from_generator(Relation#relation.name, Relation#relation.generator) end end. -%% @doc Create an iterator for streaming tuples from a relation. -%% -%% Implements the Volcano Iterator Model: spawns an independent process that -%% lazily streams tuples from the relation. This enables: -%% <ul> -%% <li>Memory-bounded queries (tuples materialized on demand)</li> -%% <li>Composable query operators (future: select, project, join)</li> -%% <li>Process-based concurrency</li> -%% </ul> -%% -%% The iterator process responds to `{next, Caller}' messages and sends back -%% either `{tuple, Tuple}' or `done' when exhausted. -%% -%% <b>Note:</b> For infinite relations, use `get_tuples_iterator/3' with constraints. -%% -%% == Example == -%% <pre> -%% Iterator = operations:get_tuples_iterator(DB, users), -%% {ok, Tuple} = operations:next_tuple(Iterator), -%% operations:close_iterator(Iterator). -%% </pre> -%% -%% @param Database `#database_state{}' record -%% @param RelationName Atom naming the relation to iterate -%% @returns Pid of iterator process -%% -%% @see get_tuples_iterator/3 -%% @see next_tuple/1 -%% @see close_iterator/1 -%% @see collect_all/1 -get_tuples_iterator(Database, RelationName) when is_record(Database, database_state) -> - get_tuples_iterator(Database, RelationName, #{}). +%% @doc Get an iterator out of a generator. +get_iterator_from_generator(RelationName, GeneratorFun) -> + case GeneratorFun of + undefined -> spawn(fun() -> tuple_iterator_loop([]) end); + Generator when is_function(Generator) -> Generator(); + _ -> erlang:error({error_tuple_iterator_init, non_function_generator, RelationName}) + end. %% @doc Get next tuple from iterator. %% @@ -946,24 +796,20 @@ close_iterator(IteratorPid) -> %% </ul> %% %% @param TupleHashes List of binary tuple hashes to stream -%% @param RelationName Name of the source relation (for provenance) -%% @param EnableProvenance Boolean flag to enable provenance tracking -tuple_iterator_loop([], _RelationName, _EnableProvenance) -> +tuple_iterator_loop([]) -> receive {next, Caller} -> Caller ! done; stop -> ok end; -tuple_iterator_loop([TupleHash | Rest], RelationName, EnableProvenance) -> +tuple_iterator_loop([TupleHash | Rest]) -> receive {next, Caller} -> %% Resolve tuple on demand ResolvedTuple = resolve_tuple(TupleHash), - %% Add provenance tracking (always enabled) - FinalTuple = add_base_provenance(ResolvedTuple, RelationName), - Caller ! {tuple, FinalTuple}, - tuple_iterator_loop(Rest, RelationName, EnableProvenance); + Caller ! {tuple, ResolvedTuple}, + tuple_iterator_loop(Rest); stop -> ok end. @@ -1003,10 +849,6 @@ collect_all(IteratorPid, Acc) -> {error, Reason, lists:reverse(Acc)} end. -%%% ============================================================================ -%%% Iterator Operators (Lazy - Volcano Model) -%%% ============================================================================ - %% @doc Select iterator: Filters tuples based on a predicate. %% %% Lazy operator that wraps a child iterator and only emits tuples that @@ -1032,12 +874,9 @@ select_loop(ChildPid, Predicate) -> {ok, Tuple} -> case Predicate(Tuple) of true -> - %% Wrap lineage with select operation - TupleWithLineage = wrap_lineage(Tuple, {select, Predicate}), - Caller ! {tuple, TupleWithLineage}, + Caller ! {tuple, Tuple}, select_loop(ChildPid, Predicate); false -> - %% Skip this tuple, get next self() ! {next, Caller}, select_loop(ChildPid, Predicate) end; @@ -1076,30 +915,9 @@ project_loop(ChildPid, Attributes) -> {next, Caller} -> case next_tuple(ChildPid) of {ok, Tuple} -> - % Project data attributes + % Project data attributes only - no metadata handling ProjectedTuple = maps:with(Attributes, Tuple), - - % Preserve and update metadata - case maps:get(meta, Tuple, undefined) of - undefined -> - % No metadata, just return projected tuple - Caller ! {tuple, ProjectedTuple}; - Meta -> - % Filter provenance to only projected attributes - OldProv = maps:get(provenance, Meta, #{}), - NewProv = maps:with(Attributes, OldProv), - - % Build new metadata - UpdatedMeta = case NewProv of - Empty when map_size(Empty) =:= 0 -> maps:remove(provenance, Meta); - _ -> maps:put(provenance, NewProv, Meta) - end, - - % Add metadata back and wrap lineage - TupleWithMeta = maps:put(meta, UpdatedMeta, ProjectedTuple), - TupleWithLineage = wrap_lineage(TupleWithMeta, {project, Attributes}), - Caller ! {tuple, TupleWithLineage} - end, + Caller ! {tuple, ProjectedTuple}, project_loop(ChildPid, Attributes); done -> close_iterator(ChildPid), @@ -1135,17 +953,11 @@ project_loop(ChildPid, Attributes) -> %% @returns Iterator process (Pid) sort_iterator(ChildIterator, CompareFun) when is_function(CompareFun, 2) -> spawn(fun() -> - %% Phase 1: Consume all tuples (blocking!) + %% Sync all state blocking the pipeline AllTuples = collect_all(ChildIterator), - - %% Phase 2: Sort in memory + %% Sort in memory SortedTuples = lists:sort(CompareFun, AllTuples), - - %% Phase 3: Wrap lineage for all tuples - TuplesWithLineage = [wrap_lineage(T, {sort, CompareFun}) || T <- SortedTuples], - - %% Phase 4: Emit sorted tuples on demand - sorted_emit_loop(TuplesWithLineage) + sorted_emit_loop(SortedTuples) end). sorted_emit_loop([]) -> @@ -1184,9 +996,8 @@ take_iter_loop(ChildPid, Limit, Count, OriginalN) when Count < Limit -> {next, Caller} -> case next_tuple(ChildPid) of {ok, Tuple} -> - %% Wrap lineage with take operation - TupleWithLineage = wrap_lineage(Tuple, {take, OriginalN}), - Caller ! {tuple, TupleWithLineage}, + %% Pass through tuple without metadata injection + Caller ! {tuple, Tuple}, take_iter_loop(ChildPid, Limit, Count + 1, OriginalN); done -> close_iterator(ChildPid), @@ -1305,7 +1116,7 @@ materialize(Database, SourceIterator, ResultName) when is_record(Database, datab {DB1, _Relation} = create_relation(Database, ResultName, Schema), %% 4. Insert all tuples - {FinalDB, FinalRelation} = insert_all_tuples(DB1, ResultName, AllTuples), + {FinalDB, FinalRelation} = create_all_tuples(DB1, ResultName, AllTuples), {FinalDB, FinalRelation} end. @@ -1327,7 +1138,7 @@ infer_type(_) -> term. %% @private %% Insert multiple tuples into a relation. -insert_all_tuples(DB, RelationName, Tuples) -> +create_all_tuples(DB, RelationName, Tuples) -> lists:foldl( fun(Tuple, {DBacc, _RelAcc}) -> create_tuple(DBacc, RelationName, Tuple) @@ -1340,51 +1151,20 @@ insert_all_tuples(DB, RelationName, Tuples) -> %%% Generator Support Functions %%% ============================================================================ -%% Instantiate a generator from a generator specification (commented out). -%% Converts a generator spec (stored in relation record) into an actual -%% generator function that can produce tuples. -%% -%% @param GeneratorSpec Generator specification -%% @param Constraints Boundedness constraints -%% @returns Generator function -%% instantiate_generator({primitive, naturals}, Constraints) -> -%% generators:naturals(Constraints); -%% instantiate_generator({primitive, integers}, Constraints) -> -%% generators:integers(Constraints); -%% instantiate_generator({primitive, rationals}, Constraints) -> -%% generators:rationals(Constraints); -%% instantiate_generator({primitive, plus}, Constraints) -> -%% generators:plus(Constraints); -%% instantiate_generator({primitive, times}, Constraints) -> -%% generators:times(Constraints); -%% instantiate_generator({primitive, minus}, Constraints) -> -%% generators:minus(Constraints); -%% instantiate_generator({primitive, divide}, Constraints) -> -%% generators:divide(Constraints); -%% instantiate_generator({custom, GeneratorFun}, Constraints) -> -%% GeneratorFun(Constraints); -%% instantiate_generator({take, RelationName, N}, Constraints) -> -%% %% Take generator: wrap another generator with limit -%% %% This is a simplified version - full implementation would look up the base relation -%% make_take_generator(RelationName, N, Constraints); -%% instantiate_generator(Other, _) -> -%% erlang:error({unknown_generator, Other}). %% @private %% Generator iterator loop for infinite relations. %% Similar to tuple_iterator_loop but works with generator functions instead %% of tuple hashes. -generator_iterator_loop(Generator, RelationName, EnableProvenance) -> +generator_iterator_loop(Generator) -> receive {next, Caller} -> case Generator(next) of done -> Caller ! done; - {value, Tuple, NextGen} -> - %% Add provenance tracking (always enabled) - FinalTuple = add_base_provenance(Tuple, RelationName), - Caller ! {tuple, FinalTuple}, - generator_iterator_loop(NextGen, RelationName, EnableProvenance); + {value, Tuple, NextGenerator} -> + Caller ! {tuple, Tuple}, + generator_iterator_loop(NextGenerator); {error, Reason} -> Caller ! {error, Reason} end; @@ -1423,7 +1203,7 @@ equijoin_emit_loop(LeftIter, RightTuples, JoinAttr) -> equijoin_emit_loop(LeftIter, RightTuples, JoinAttr); LeftValue -> % Find matching right tuples - Matches = [merge_tuples(LeftTuple, RightTuple, {equijoin, JoinAttr}) + Matches = [merge_tuples(LeftTuple, RightTuple) || RightTuple <- RightTuples, maps:get(JoinAttr, RightTuple, undefined) =:= LeftValue], case Matches of @@ -1478,7 +1258,7 @@ theta_join_emit_loop(LeftIter, RightTuples, Pred) -> Caller ! done; {ok, LeftTuple} -> % Find all right tuples that satisfy predicate - Matches = [merge_tuples(LeftTuple, RightTuple, {theta_join, Pred}) + Matches = [merge_tuples(LeftTuple, RightTuple) || RightTuple <- RightTuples, Pred(LeftTuple, RightTuple)], case Matches of @@ -1512,133 +1292,64 @@ theta_join_emit_buffered(LeftIter, RightTuples, Pred, []) -> theta_join_emit_loop(LeftIter, RightTuples, Pred). %% @private -%% Wrap existing lineage with a new operation. -%% Takes a tuple with optional lineage and wraps it with a new operation node. -%% If the tuple has no lineage, does nothing. -%% -%% @param Tuple Tuple potentially with meta.lineage -%% @param OpInfo Operation info: {select, Pred} | {project, Attrs} | {sort, Cmp} | {take, N} -wrap_lineage(Tuple, OpInfo) -> - case maps:get(meta, Tuple, undefined) of - undefined -> - % No metadata, return as-is - Tuple; - Meta -> - case maps:get(lineage, Meta, undefined) of +%% @doc Simple tuple merge for joins +%% Equally named and typed attributes are not repeated. +%% +%% @param LeftTuple Left side tuple +%% @param RightTuple Right side tuple +merge_tuples(LeftTuple, RightTuple) -> + maps:fold( + fun(RightKey, RightValue, LeftTupleAcc) -> + case maps:get(RightKey, LeftTupleAcc, undefined) of + LeftValue when LeftValue =:= RightValue -> + % Equal attributes, keep single value + LeftTupleAcc; undefined -> - % No lineage, return as-is - Tuple; - ChildLineage -> - % Wrap existing lineage with new operation - NewLineage = case OpInfo of - {select, Pred} -> {select, Pred, ChildLineage}; - {project, Attrs} -> {project, Attrs, ChildLineage}; - {sort, CmpFun} -> {sort, CmpFun, ChildLineage}; - {take, N} -> {take, N, ChildLineage} - end, - maps:put(meta, maps:put(lineage, NewLineage, Meta), Tuple) + % No conflict, add right attribute + maps:put(RightKey, RightValue, LeftTupleAcc); + _ -> + % Different attributes + maps:put(RightKey, RightValue, LeftTupleAcc) end - end. - -%% @private -%% Add base provenance and lineage to a tuple from a relation. -%% Creates nested meta fields with both provenance and lineage. -%% Example: add_base_provenance(#{id => 1, name => "Alice"}, employees) -%% => #{id => 1, name => "Alice", -%% meta => #{provenance => #{id => {employees, id}, name => {employees, name}}, -%% lineage => {base, employees}}} -add_base_provenance(Tuple, RelationName) -> - % Build provenance map for all attributes (excluding existing meta) - DataAttrs = maps:remove(meta, Tuple), - Provenance = maps:fold( - fun(Key, _Value, Acc) -> - maps:put(Key, {RelationName, Key}, Acc) end, - #{}, - DataAttrs - ), - % Add metadata with provenance and lineage - maps:put(meta, #{ - provenance => Provenance, - lineage => {base, RelationName} - }, Tuple). + LeftTuple, + RightTuple + ). %% @private -%% Merge two tuples for join result, including metadata. -%% If attribute names conflict, right side attributes are prefixed with "right_". -%% Metadata (including provenance and lineage) is also merged. -%% -%% @param LeftTuple Left side tuple -%% @param RightTuple Right side tuple -%% @param JoinInfo Join information: {equijoin, Attr} | {theta_join, Predicate} -merge_tuples(LeftTuple, RightTuple, JoinInfo) -> - % Extract metadata from both sides (if present) - LeftMeta = maps:get(meta, LeftTuple, #{}), - RightMeta = maps:get(meta, RightTuple, #{}), - - % Extract provenance and lineage from metadata - LeftProv = maps:get(provenance, LeftMeta, #{}), - RightProv = maps:get(provenance, RightMeta, #{}), - LeftLineage = maps:get(lineage, LeftMeta, undefined), - RightLineage = maps:get(lineage, RightMeta, undefined), - - % Remove metadata from tuples for data merging - LeftData = maps:remove(meta, LeftTuple), - RightData = maps:remove(meta, RightTuple), - - % Merge data attributes - MergedData = maps:fold( - fun(Key, Value, Acc) -> - case maps:is_key(Key, Acc) of - true -> - % Conflict - prefix right attribute - RightKey = list_to_atom("right_" ++ atom_to_list(Key)), - maps:put(RightKey, Value, Acc); - false -> - maps:put(Key, Value, Acc) - end - end, - LeftData, - RightData - ), - - % Merge provenance (same conflict resolution) - MergedProv = maps:fold( - fun(Key, Source, Acc) -> - case maps:is_key(Key, Acc) of - true -> - % Conflict - prefix right attribute provenance - RightKey = list_to_atom("right_" ++ atom_to_list(Key)), - maps:put(RightKey, Source, Acc); - false -> - maps:put(Key, Source, Acc) - end +%% Build base provenance mapping for a relation. +%% Maps each attribute to its source relation and attribute name. +%% +%% @param Schema Map of attribute names to types +%% @param RelationName Name of the source relation +%% @returns Provenance map #{attr => {relation, attr}} +build_base_provenance(Schema, RelationName) -> + maps:fold( + fun(AttrName, _Type, Acc) -> + maps:put(AttrName, {RelationName, AttrName}, Acc) end, - LeftProv, - RightProv - ), - - % Build merged lineage if both sides have lineage - MergedLineage = case {LeftLineage, RightLineage, JoinInfo} of - {undefined, undefined, _} -> undefined; - {L, R, {equijoin, Attr}} when L =/= undefined, R =/= undefined -> - {join, Attr, L, R}; - {L, R, {theta_join, Pred}} when L =/= undefined, R =/= undefined -> - {theta_join, Pred, L, R}; - _ -> undefined - end, + #{}, + Schema + ). - % Build merged metadata - MergedMeta = case {maps:size(MergedProv), MergedLineage} of - {0, undefined} -> #{}; - {0, Lineage} -> #{lineage => Lineage}; - {_, undefined} -> #{provenance => MergedProv}; - {_, Lineage} -> #{provenance => MergedProv, lineage => Lineage} - end, +%% The issue here is that the creation of a generator on the create_relation is wrong. +%% I assume it was because of the fun(Constraints), which I believe should receive an +%% optional database version, or just build from the current relation attributes as a factory. - % Add merged metadata to result (only if non-empty) - case maps:size(MergedMeta) of - 0 -> MergedData; - _ -> maps:put(meta, MergedMeta, MergedData) +%% @private +%% @doc Create a generator function from a list of tuple hashes. +%% +%% Converts a list of tuple hashes into a generator function compatible +%% with the generator protocol used by infinite relations. The generator +%% reads tuples from Mnesia on demand. +%% +%% @param TupleHashes List of tuple hashes to iterate over +%% @returns Generator function that accepts 'next' and returns {value, Tuple, NextGen} or done +make_finite_generator([]) -> + fun(_) -> done end; +make_finite_generator([Hash | Rest]) -> + fun(next) -> + ResolvedTuple = resolve_tuple(Hash), + NextGen = make_finite_generator(Rest), + {value, ResolvedTuple, NextGen} end. - |