proto: split proto-files

This splits the proto file into three files: aeon_sql.proto,
aeon_crud.proto, and aeon_common.proto.

This patch also adds a warning that CRUD operations are experimental.

Closes #2

aeon_common.proto

@@ -0,0 +1,185 @@
+syntax = "proto3";
+
+package aeon;
+
+option go_package = "./pb";
+
+// Common API to Aeon - a distributed database based on Tarantool.
+service CommonService {
+  //
+  // Diagnostic requests.
+  //
+
+  // Pings the router.
+  rpc Ping(PingRequest) returns (PingResponse) {}
+}
+
+//
+// Common structures.
+//
+
+// Special value denoting null.
+enum NullValue { NULL_VALUE = 0; }
+
+// Array of arbitrary-typed values.
+message ArrayValue { repeated Value fields = 1; }
+
+// Map with string keys and arbitrary-typed values..
+message MapValue { map<string, Value> fields = 1; }
+
+// Date time value.
+message DateTimeValue {
+  int64 seconds = 1;
+  int64 nsec = 2;
+  string location = 3;
+}
+
+// Date time interval value.
+message IntervalValue {
+  enum IntervalAdjust {
+    INTERVAL_ADJUST_NONE = 0;
+    INTERVAL_ADJUST_EXCESS = 1;
+    INTERVAL_ADJUST_LAST = 2;
+  }
+  int64 year = 1;
+  int64 month = 2;
+  int64 week = 3;
+  int64 day = 4;
+  int64 hour = 5;
+  int64 min = 6;
+  int64 sec = 7;
+  int64 nsec = 8;
+  IntervalAdjust adjust = 9;
+}
+
+// Arbitrary value that can be serialized to be sent over the network or
+// stored in the database.
+message Value {
+  oneof kind {
+    uint64 unsigned_value = 1;
+    string string_value = 2;
+    double number_value = 3;
+    sint64 integer_value = 4;
+    bool boolean_value = 5;
+    bytes varbinary_value = 6;
+    string decimal_value = 7;
+    string uuid_value = 8;
+    DateTimeValue datetime_value = 9;
+    IntervalValue interval_value = 10;
+    ArrayValue array_value = 11;
+    MapValue map_value = 12;
+    NullValue null_value = 13;
+  }
+}
+
+// Error information.
+message Error {
+  // Error type.
+  // * AeonError for core Aeon errors.
+  // * AeonSQLError for issues with SQL parsing.
+  // * AeonGRPCError for issues with gRPC encoding.
+  string type = 1;
+  // Error name.
+  string name = 2;
+  // Error location: file, line.
+  string file = 3;
+  uint64 line = 4;
+  // Human-readable error description.
+  string msg = 5;
+  // System errno (usually not set).
+  uint64 errno = 6;
+  // Error code.
+  uint64 code = 7;
+  // Fields with extra information.
+  MapValue fields = 8;
+  // Previous error on the error stack (cause of this error).
+  Error prev = 9;
+}
+
+// Tuple: array of values.
+message Tuple { repeated Value fields = 1; }
+
+// Tuple format: array of field names.
+message TupleFormat { repeated string names = 1; }
+
+// Read or write operation executed in a transaction.
+message Operation {
+  // Target space name.
+  string space = 1;
+  // Target key in the space. Must be full (have all defined key parts).
+  Tuple key = 2;
+  // In a request:
+  // * Ignored for read operations.
+  // * Specifies the tuple to write in a write operation.
+  // In a response:
+  // * Tuple read from or written to the target space.
+  // The write operation type depends on the tuple value:
+  // * NOP if the tuple is not set.
+  // * DELETE if the tuple is set but has no fields.
+  // * REPLACE otherwise. The tuple must match the target key.
+  // The tuple may be overwritten by the user-defined function specified in
+  // a request to change the written value or even operation type depending on
+  // read values.
+  Tuple tuple = 3;
+}
+
+// Type a space field can have.
+enum FieldType {
+  FIELD_TYPE_UNSPECIFIED = 0;
+  FIELD_TYPE_ANY = 1;
+  FIELD_TYPE_UNSIGNED = 2;
+  FIELD_TYPE_STRING = 3;
+  FIELD_TYPE_NUMBER = 4;
+  FIELD_TYPE_DOUBLE = 5;
+  FIELD_TYPE_INTEGER = 6;
+  FIELD_TYPE_BOOLEAN = 7;
+  FIELD_TYPE_VARBINARY = 8;
+  FIELD_TYPE_SCALAR = 9;
+  FIELD_TYPE_DECIMAL = 10;
+  FIELD_TYPE_UUID = 11;
+  FIELD_TYPE_DATETIME = 12;
+  FIELD_TYPE_INTERVAL = 13;
+  FIELD_TYPE_ARRAY = 14;
+  FIELD_TYPE_MAP = 15;
+}
+
+// Space field definition.
+message FieldDef {
+  // Field name.
+  string name = 1;
+  // Field type.
+  FieldType type = 2;
+  // If set to true, the field may store null values. Optional.
+  bool is_nullable = 3;
+}
+
+// Key part definition.
+message KeyPartDef {
+  enum KeyPartSortOrder {
+    KEY_PART_SORT_ORDER_ASC = 0;
+    KEY_PART_SORT_ORDER_DESC = 1;
+  }
+  // Indexed field ordinal number (1-based) or name.
+  oneof field {
+    uint64 id = 1;
+    string name = 2;
+  }
+  // Key part type. Optional: if omitted, it will be deduced from
+  // the corresponding space field type.
+  FieldType type = 3;
+  // Sorting order: ascending (default) or descending.
+  KeyPartSortOrder sort_order = 4;
+}
+
+//
+// Diagnostic requests.
+//
+
+// Pings the router.
+
+message PingRequest {}
+
+message PingResponse {
+  // Error information. Set only on failure.
+  Error error = 1;
+}