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v4.0
    v4.0

    Basic Concepts

    Ultipa (Ultipa Graph HTAP System, hereinafter Ultipa Graph) is a set of ultra-high performance native graph computing service framework and storage infrastructure.

    Ultipa Graph product matrix contains the followings:

    1. World's fastest real-time graph computing engine;
    2. High performance, high availability, persistent storage services;
    3. Concise and smooth user graphical operation interface and knowledge graph system;
    4. Feature rich CLI toolkit;
    5. High performance and flexible import/export toolkit;
    6. Easy to deploy docker images;
    7. SDKs and APIs of mainstream programming languages;
    8. UQL - a Graph Query Language (GQL) - that this manual focuses on.

    Ultipa Graph supports a rich collection of querying methods, loads of ultra-high performance graph algorithms, and real-time processing against large amounts of data, which truly saves a lot of time from user's perspective by upgrading very time consuming and non-real-time operations to real-time operations. It brings inestimable possibilities for graph computing products to be widely used in business and big data analytics scenarios.

    What is UQL

    Ultipa Query Language, or UQL (or uQL) for short, is a general purpose Graph Query Language. UQL is a unique high performance query and management language designed for Ultipa Graph Database and Graph Computing Engine, developers can quickly grasp it and get started with Ultipa Graph system. UQL supports query, deletion, modification, addition, graph traversal, subgraph matching, schema management, property management, engine management, index management, GraphSet management, task management, permission management, and other functions on Ultipa Graph system. Users can invoke UQL via Ultipa CLI (Command Line Tool), Ultipa Manager (a graphical interface) or SDK (Ultipa Software Development Kits). UQL will soon achieve Turing Completeness and be available to developers.

    UQL keeps pace with GQL international standards in terms of the overall functionality and compatibility. GQL standard is expected to be launched in 2022. Ultipa team has begun to join the standardization organization to build the standard Graph Query Language.

    Terminologies

    Name
    Description
    GQL Graph Query Language, another and the only standard data query language since SQL (Structured Query Language).
    UQL (uQL) Ultipa Graph Query Language, a kind of GQL that can fully operate Ultipa Graph system.
    Node In graph theory, a node is formally called a "vertex". In Ultipa Graph, we call vertex "node".
    Edge Edge connects a pair of nodes, all the edges in Ultipa Graph system are directed edge (see the description of "Direction" below).
    Path Path is a sequence with definite initial-node and terminal-node, alternating between nodes and edges. Nodes in path can correspond while edges cannot. The sequence of the nodes and edges in a path can be regarded as a unique identifier of the path.
    Circle (V4.0) Observe nodes of a path excluding the initial-node, if any two nodes correspond then the path is judged as 'with circle'.
    (V4.1) For a path where the initial-node and the terminal-node do not correspond, it is judged as 'with circle' if any two nodes correspond, for a path where the initial-node and the terminal-node correspond, the judgement is consistent with V4.0.

    (Paths with circle can be ruled out by using the parameter no_circle() in path query command so they will not be returned.)
    Shortest Path If a path contains the least number of edges, at least one edge, to walk from its initial-node to terminal-node, it is called a shortest path of the specified initial-node and terminal-node. The 'least number of edges' should be understood as 'minimum sum of edges weights' in case of a weighted path.
    Graph Dataset of nodes and edges is called graph. Graph can be viewed as a data collection of multiple paths. The smallest unit of graph is node.
    Subgraph Subgraph is part of nodes and edges of the whole graph. The result of node query and path query can be considered as a subgraph.
    GraphSet A GraphSet comprises a set of nodes and edges along with indexes, user privilleges and algorithmic tasks created on the graph. In Ultipa Graph system, user can create more than one GraphSet.
    Schema In Ultipa Graph system, a schema of node or edge includes a set of properties that describes the structure and content of node or edge. Each node or edge can only belong to one schema.
    Property A property belongs to a schema and is used to describe a character of node or edge. Property supports rich data types such as int32, float, string, and some data structures such as array, dictionary.
    Property Index Index mechanism is used to improve the query efficiency of properties, the created index tree is stored on the disk.
    Full-text Index Full-text index (word-segmentation of the text) is created to improve the query efficiency of long strings. Full-text index supports different dictionaries in order to optimize the word-segmentation for different datasets.
    Engine Index Improving the efficiency of path query and deep graph traversal by loading properties to the computing engine, the efficiency is often increased by several orders of magnitude.
    Instance Ultipa Graph system instances, that is, the running applications on Ultipa Server, each instance generally runs on one virtual or physical host, and multiple instances can form a cluster environment.
    Filter It is used to filter nodes and edges during graph queries. Ultipa filter is essentially a logic tree, very much like IF in programming languages, which uses various conditional operators, logical operators and numeric operators. Refer to the chapter Filter for details.
    LTE Load to Engine, load property to the computing engine.
    UFE Unload from Engine, remove property from the computing engine.
    Direction (In) An edge pointing to node A from another node is called an "In" edge of node A, or an edge of node A in the inbound direction. It is written as either A<-- or -->A.
    Direction (Out) An edge pointing from node A to another node is called an "Out" edge of node A, or an edge of node A in the outbound direction. It is written as either A--> or <--A.
    Direction (Left) An edge in a given path that points from the latter node to the previous node is called "Left" edge. It is written as A<--B.
    Direction (Right) An edge in a given path that points from the previous node to the latter node is called "Right" edge. It is written as A-->B.
    ID (_id) Unique identifier that is exclusive to node. It is stored as string with maximum length of 128.
    UUID (_uuid) Unique identifier for nodes and edges. It is stored as uint64.
    Edge Start (_from, _from_uuid) The ID or UUID of the start node of directed edge.
    Edge End (_to, _to_uuid) The ID or UUID of the end node of directed edge.
     V4.1  Features introduced in V4.1.

    Specification

    The design inspiration of UQL has roots in a deep understanding of graph, and it satisfies the demands of industry for high dimensional and extensible graphs.

    Chain Statement + Semantic Assembly + Alias Call

    UQL Example:

    n(1).e({time > prev_e.time})[3].n(as target)
    group by target.level with count(target) as quantity
    order by quantity desc
    return target.level, quantity limit 10

    Instructions:

    • The n(... ).e(...)[3].n(...) in the above example is a chain statement styled as [command].[parameter].[parameter].... It realizes the operations of insertion, update, deletion and query of a UQL. A UQL statement may contain multiple chain statements.
    • The group by ..., with ..., order by ..., return ... and limit ... from the above example are clauses that process and assemble query results of a UQL.
    • The query results of a UQL can also be recomputed by a function, such as the count(...) in the above example.
    • Query results that are temporarily saved and passed between chain statements and clauses should be given custom alias, such as target and quantity in the example. Use as to define a custom alias.
    • Query results that are passed within a multi-edge template are entitled with system alias, the prev_n and prev_e, to be called by an Ultipa Filter. Refer to the usage of ...time > prev_e.time... in the example.
    • Supports escape characters \, tab \t, carriage return line feed \r\n and comment delimiters //, /* and */.

    UQL Design Principles:

    • Ability to return and use high dimensional results;
    • Advanced and clearly defined data structures, such as subgraph, path, node, edge, property, array and table;
    • Easy depict of subgraph filtering, direct docking and adaptation to high performance computing engine;
    • Minimal cognitive loading, easy to read, write and learn;
    • Chain statement + semantic assembly, various functional extensions supported, the "chain" itself is a path;
    • The functional style is more in line with today's complex data processing needs, and provides unlimited expansion space;
    • The functional style allows users to customize the extended language syntax features to meet the demands of operating complex graph;

    Why Not SQL-like:

    • SQL's inability to clearly express high dimensional data and its combinations, such as path, node, edge, property and collection of aggregation operation results;
    • Path filtering in SQL is too complicated and inefficient, such as path query, template query and graph traversal;
    • It is difficult to understand SQL as it is contrary to the logic of human brain, such as nested statement, join table query, etc.

    UQL Syntax Features

    UQL has DQL, DDL, DML and DCL syntax features:

    • DQL: Data Query Language, to query nodes, edges and paths in the graph;
    • DDL: Data Definition Language, to add, delete, modify and view the content of GraphSet;
    • DML: Data Manipulation Language, to add/delete GraphSet, modify schema, control index etc.;
    • DCL: Data Control Language, mainly used to manipulate database permission settings, such as user management, role management, the grant and revoke of permissions etc.

    Naming Conventions

    When defining the name of graph, schema, property, alias, index, policy, user and so on in UQL, the general naming conventions are as below:

    • 2~64 characters (1~64 for alias)
    • Must start with letters
    • Allow to use letters, underscore and numbers ( _ , A-Z, a-z, 0-9)

    Special cases are described separately when introducing the relevant content.

    Custom names are case sensitive. For example, GraphSet "Bank" and "bank" are regarded as two different GraphSets.

    Reserved Words

    Word Category Description
    properties begin with _ reserved character for system properties system defined property, such as _id, _uuid, _from, _to, _from_uuid, _to_uuid
    full-text filters begin with ~ reserved character for full-text filter the full-text filter that is being called, i.e. prefix ~ to the name of the full-text index
    prev_n system alias previous node of the current node/edge in template query (case sensitive)
    prev_e system alias previous edge of the current node/edge in template query (case sensitive)
    this system alias current node/edge in various queries, only used to disambiguate UQL statements (case sensitive)
    in conditional operator to judge whether an operand exists in a set
    nin conditional operator to judge whether an operand does not exist in a set
    contains conditional operator to judge whether a full-text index contains one or multiple values
    xor logical operator to judge whether one of the two operands is true while the other is false  V4.1 
    as clause keyword to define alias
    group by clause keyword to group the rows in data stream, it is a combination of group and by
    order by clause keyword to sort the rows in data stream, it is a combination of oder and by
    asc, desc clause keyword to define the order is ascending or descending in order by operation
    skip clause keyword to discard the first N rows of the data stream
    limit clause keyword to keep the first N rows of the data stream
    return clause keyword to assemble the return values
    with clause keyword to assemble the values and to pass backwards
    where clause keyword to filter the rows in data stream
    uncollect clause keyword to expand the array elements in the column
    union, all clause keyword to splice two columns into one column  V4.1 
    call clause keyword to call a sub-query  V4.1 
    case function keyword to map the rows in data stream
    when function keyword to define the conditions that the rows have to meet in case
    then function keyword the value after mapping of the rows that meet the conditions in case
    else function keyword the value after mapping of the rows that does not meet the conditions in case
    end function keyword to end case mapping
    exec task task prefix to run non-algorithm UQLs in an analysis node in the Ultipa server
    optional no-return prefix to return a pseudo result for the queries that have no return, can be a node, an edge, or a path whose UUID is 0
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