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AgensGraph Quick Guide Copyright Notice Copyright © 2016, Bitnine Inc. All Rights Reserved. Restricted Rights Legend PostgreSQL is Copyright © 1996-2016 by the PostgreSQL Global Development Group. Postgres95 is Copyright © 1994-5 by the Regents of the University of California. AgensGraph is Copyright © 2016 by Bitnine Inc. Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies. IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN ”AS-IS” BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. Trademarks AgensGraph® is a registered trademark of Bitnine Inc. Other products, titles or services may be registered trademarks of their respective companies. Open Source Software Notice Some modules or files of this product are subject to the terms of the following licenses. : OpenSSL, RSA Data Security, Inc., Apache Foundation, Jean-loup Gailly and Mark Adler, Paul Hsieh’s hash. Information of technical documentation Title : AgensGraph Quick Guide Published date : March 22, 2018 S/W version : AgensGraph v1.3 Technical documentation version : v1.0 Contents 1 2 3 4 5 6 7 8 9 Release Notes . . . . . . . . . . . . . . . . . . . . Overview . . . . . . . . . . . . . . . . . . . . . . 2.1 Basic information . . . . . . . . . . . . . . 2.2 AgensGraph Introduction . . . . . . . . . 2.3 Features . . . . . . . . . . . . . . . . . . . Installation . . . . . . . . . . . . . . . . . . . . . 3.1 Installation of pre-built packages . . . . . 3.2 Installation of build source code . . . . . . 3.3 Post-Installation Setup and Configuration 3.4 Configuring Server Parameters . . . . . . Data Model . . . . . . . . . . . . . . . . . . . . . 4.1 AgensGraph Data Model . . . . . . . . . . 4.2 Data Definition Language . . . . . . . . . AgensGraph Query . . . . . . . . . . . . . . . . . 5.1 Graph Query . . . . . . . . . . . . . . . . 5.2 Hybrid Query . . . . . . . . . . . . . . . . Graph Data Import . . . . . . . . . . . . . . . . . Tools . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Command Line Interface Tool . . . . . . . Client Drivers . . . . . . . . . . . . . . . . . . . . 8.1 Java Driver . . . . . . . . . . . . . . . . . External Modules . . . . . . . . . . . . . . . . . . 9.1 External Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7 7 8 8 9 9 9 10 10 12 12 14 22 22 27 29 32 32 33 33 37 37 About technical documentation Objective of technical documentation This technical article is described for application program developers who wish to develop programs using various application libraries provided by AgensGraph® (hereinafter referred to as ”AgensGraph”), a database administrator (hereinafter referred to as ”DBA”) who wants to create a database and ensure the operation of AgensGraph and all database users who want to use AgensGraph to perform database operations or to refer to Hybrid SQL for application program creation. Prerequisites for technical documentation In order to fully understand this article, you should be familiar with the following topics: • Graph Database • Relational Database • Basic Programming • Basic API • Basic knowledge of UNIX series (including Linux) Limitations of technical documentation This guide does not contain everything you need to apply or operate AgensGraph in practice. Therefore, refer to each technical manual for operation and management such as installation and environment setting. 4 AgensGraph Quick Guide Conventions of Technical Documentation Mark DescriptionThe file name of the program source code, directory [Button] Button or menu name in GUI Bold Emphasis “ ”(Quotes) Refer to other relevant guides or other chapters and sections within the guide ‘Input field’ A description of the entries in the UI Hyperlink Email account, Website > Progress of menu +— Has subdirectory or file |— No subdirectories or files Notes Notes or cautions [Figure 1.1] Figure name [Table 1.1] Table name AaBbCc123 Commands, output after execution, sample code {} Required Argument Values [] Optional Argument Value | Selection Argument Value About this document 5 Locations Korea Bitnine Inc. A1201 GangSeo Hangang Xi Tower 401, Yangcheon-ro, Gangseo-gu, Seoul, South Korea Tel : +82-70-4800-3517 Fax : +82-70-8677-2552 Email : agens@bitnine.net Web : bitnine.net USA Bitnine Global Inc. 3945 Freedom Cir., Suite 260, Santa Clara, CA 95054 U.S.A Tel : +1 (408) 352-5165 Email : agens@bitnine.net Web : bitnine.net 6 AgensGraph Quick Guide 1 Release Notes This document is for AgensGraph v1.3 community edition. See the release link. 2 Overview 2.1 Basic information 2.1.1 About the Documentation This document is a short guide for AgensGraph developers. This guide will introduce various aspects of AgensGraph, including the data model and data de inition language, Cypher query processing abilities, and Java development capabilities. Because AgensGraph is compatible with PostgreSQL, some parts of the documentation quote parts of PostgreSQL's documentation or link to it. 2.1.2 License Creative Commons 3.0 License (https://creativecommons.org/licenses/by-sa/3.0/) PostgreSQL documentation is published using the following licence. PostgreSQL is Copyright © 1996-2016 by the PostgreSQL Global Development Group. Postgres95 is Copyright © 1994-5 by the Regents of the University of California. Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies. IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN ``AS-IS'' BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. Release Notes 7 2.2 AgensGraph Introduction 2.2.1 What is AgensGraph? AgensGraph is a new generation multi-model graph database for the modern complex data environment. AgensGraph is a multi-model database based on PostgreSQL RDBMS, and supports both relational and graph data models at the same time. This enables developers to integrate the legacy relational data model and the lexible graph data model in one database. AgensGraph supports Ansi-SQL and Open Cypher (http://www.opencypher.org). SQL queries and Cypher queries can be integrated into a single query in AgensGraph. AgensGraph is very robust, fully-featured and ready for enterprise use. It is optimized for handling complex connected graph data and provides plenty of powerful database features essential to the enterprise database environment including ACID transactions, multi-version concurrency control, stored procedure, triggers, constraints, sophisticated monitoring and a lexible data model (JSON). Moreover, AgensGraph leverages the rich eco-systems of PostgreSQL and can be extended with many outstanding external modules, like PostGIS. 2.3 Features • Multi-model support of the property graph data model, relational data model and JSON documents • Cypher query language support • Integrated querying using SQL and Cypher • Graph data object management • Hierarchical graph label organization • Property indexes on both vertexes and edges • Constraints: unique, mandatory and check constraints • ACID transactions • Hadoop connectivity • Active-standby replication • And many other features 2.3.1 More Information Because AgensGraph inherits all features of PostgreSQL (http://postgresql.org), users and database administrators can refer to the documentation of PostgreSQL for more information. 8 AgensGraph Quick Guide 3 Installation AgensGraph runs on Linux and Windows. There are two methods available to install AgensGraph: downloading the binary package or compiling the package from source code. 3.1 Installation of pre-built packages 3.1.1 Installing AgensGraph on Linux 1. Get the pre-compiled binary: Visit the AgensGraph download page and download the corresponding version of AgensGraph. Tip: If you do not know your system environment, you can use the command: uname -sm 2. Extract the package: Extract the downloaded ile into a directory for your use (for example, /usr/local/AgensGraph/ on Linux) tar xvf /path/to/your/use Note : If you want AgensGraph on other operating systems, please contact Bitnine's support team. 3.2 Installation of build source code 1. Access the AgensGraphgithub and get the source code. $ git clone https://github.com/bitnine-oss/agensgraph.git 2. Install the following essential libraries according to each OS. 1. CENTOS $ yum install gcc glibc glib-common readline readline-devel zlib zlib-devel 2. Fedora $ dnf install gcc glibc bison lex readline readline-devel zlib zlib-devel 3. Ubuntu $ sudo apt-get install build-essential libreadline-dev zlib1g-dev lex bison 3. Go to the clone location and run con igure on the source tree. The --pre ix=/path/to/intall option allows you to set the location where AgensGraph will be installed. $ ./congifure Installation 9 4. Run the build. $ make install 5. Install the extension module and binary $ make install-world 3.3 Post-Installation Setup and Configuration 1. Environment variable setting (optional): You can add these commands into a shell start-up ile, such as the ~/.bash_pro ile. export LD_LIBRARY_PATH=/usr/local/AgensGraph/lib:$LD_LIBRARY_PATH export PATH=/usr/local/AgensGraph/bin:$PATH export AGDATA=/path/to/make/db_cluster 2. Creating a database cluster*: initdb [-D /path/to/make/db_cluster] 3. Starting the server**: ag_ctl start [-D /path/created/by/initdb] 4. Creating a database**: createdb [dbname] If dbname is not speci ied, a database with the same name as the current user is created, by default. 5. Execute the interactive terminal: agens [dbname] If the db_cluster directory is not speci ied with -D option, the environment variable AGDATA is used. 3.4 Configuring Server Parameters In order to attain optimal performance, it is very important to set server parameters correctly according to the size of data and machine resources. Among many server parameters, the following parameters are crucial for AgensGraph graph query performance. (You can edit $AGDATA/postgresql.conf ile to set these parameters (restart required)). 10 AgensGraph Quick Guide • shared_buffers: The size of memory for caching data objects. This parameter should be increased for the production environment. It is optimal when it is as large as the data size. But, this parameter should be set carefully considering concurrent sessions and memory size allocated for each queries. The recommended setting is half of the physical memory size. • work_mem: This shoud be also increased according to the size of physical memory and the properties of queries that will be executed carefully. • random_page_cost: This parameter is for query optimization. For graph queries, it is recommended to reduce this value to 1 or 0.005 (in case graph data is fully cached in memory). For more information, you can refer to PostgreSQL documentation. Installation 11 4 Data Model 4.1 AgensGraph Data Model AgensGraph is a multi-model database. AgensGraph simultaneously supports both the property graph model and the relational model. 4.1.1 Property Graph Model Figure 1.1: Labeled Property Graph Model The property graph model contains connected entities, which can have any number of attributes. In AgensGraph, an entity is known as a vertex. Vertices can have an arbitrary number of attributes and can be categorized with labels. Labels are used to group vertices in order to represent some categories of vertices; i.e. representing the role of a person. Edges are directed connections between two vertices. Edges can also have attributes and categorized labels like vertices. In AgensGraph, an edge always has a start vertex and an end vertex. If a query tries to delete a vertex, it must delete all its edges irst. Broken edges cannot exist in AgensGraph. Properties of edges and vertices are represented in the JSON format. JSON is a text format for the serialization of semi-structured data. JSONs are comprised of six data types: strings, numbers, booleans, null, objects and arrays. AgensGraph objects take full advantage of the JSON format by storing information as unordered collections of zero or more name/value pairs. A name is a string and a value can be any aforementioned type, including nested JSON types. AgensGraph speci ically uses the JSONB format. Since JSONB is a decomposed binary format, it is processed much faster than regular JSON, but at the cost of a slightly slower input time. 12 AgensGraph Quick Guide 4.1.2 Data Objects in AgensGraph Figure 1.2: AgensGraph Simple Data model In AgensGraph, several databases can be created and each database can contain one or more schemas and graphs. Schemas are for relational tables, and graph objects are for graph data. Schema name and graph name can not be the same. Vertices and edges are grouped into labels. There are two kinds of labels: vertex labels and edge labels. Users can create several graphs in a database but only one graph could be used at one time. 4.1.3 Labels Labels are used to group vertices and edges. Users can create property indexes for all vertices under a given label. Labels can be used to provide access controls for different types of users, and label hierarchies can be created to add inheritance to labels. There is default labels for vertices: ag_vertex. If one creates a vertex without specifying its label, then the vertex is stored in the default label. While An edge always has one label. We call vertex label and edge label as VLABEL and ELABEL respectively. • VLABEL : The vertex label. Categorizes vertices to represent their roles. – Vertex : entities which can hold attributes. • ELABEL : The edge label. Categorizes edges to represent their roles. – Edge : relationships connecting entities. Data Model 13 Figure 1.3: Edge Label inheritance example Every label inherits one or more labels. The igure above shows an example hierarchy of edge labels. The label hierachy is similar to a class hierarchy in object-oriented programming. Each parent label contains child label data. For example, given the above hierarchy, if a query matches with the edge `friends' then, the results contain the data of the `roommate' label. 4.2 Data Definition Language This section introduces DDLs for graph objects with a few examples. 4.2.1 Quick Description Graph To create a graph, use the CREATE GRAPH command. CREATE CREATE GRAPH graphname; Several graphs can be created in a database. In order to specify which graph is to be used, the session parameter graph_path is used. To show the current graph path, use the following command. SHOW graph_path; 14 AgensGraph Quick Guide When a graph is created using CREATE GRAPH, graph_path is set to the created graph if graph_path is not set. You can create multiple graphs and change graph_path to another graph using the following command: SET graph_path = graphname; The graph_path is a session variable, so every client must set the graph_path before querying the graph. Only one graph name can be speci ied for graph_path. Querying over multiple graphs is not allowed. If you set the graph_path for each user or database using the ALTER ROLE or DATABASE statement, you do not need to run the SET graph_path statement whenever you connect the database. ALTER ROLE user1 IN DATABASE gdb SET graph_path TO graphname; ALTER DATABASE gdb SET graph_path TO graphname; DROP DROP GRAPH graphname CASCADE; A graph has initial labels for vertices and edges. These labels cannot be deleted. To drop the graph, users must do so with the CASCADE option. If current graph_path is the deleted graph, then graph_path is reset to null. Labels CREATE CREATE VLABEL person; CREATE VLABEL friend inherits (person); CREATE ELABEL knows; CREATE ELABEL live_together; CREATE ELABEL room_mate inherits (knows, live_together); The keywords VLABEL and ELABEL are used for identifying vertices and edges respectively. CREATE VLABEL will create a vertex label. VLABEL can inherit VLABEL only (in other words, VLABEL cannot inherit ELABEL). inherits is an option to inherit a parent label. If not speci ied, the system sets the initial label as a parent label. Multiple inheritance is possible for creating complex labels. DROP DROP VLABEL friend; DROP VLABEL person; DROP ELABEL knows CASCADE; Data Model 15 VLABEL friend inherits person, so VLABEL person cannot be dropped directly. VLABEL friend should be dropped irst. In order to drop all child labels, the option CASCADE can be used to drop all dependencies. 4.2.2 Detailed Description GRAPH CREATE GRAPH CREATE GRAPH [ IF NOT EXISTS ] graph_name [AUTHORIZATION role_name]; • IF NOT EXISTS – Do nothing if the same name already exists • AUTHORIZATION role_name – The role name of the user who will own the new graph ALTER GRAPH ALTER GRAPH graph_name RENAME TO new_name; ALTER GRAPH graph_name OWNER TO { new_owner | CURRENT_USER | SESSION_USER }; • graph_name – The name of an existing graph. • RENAME TO new_name – This form changes the name of a graph to new_name. • OWNER TO new_owner – This form changes the owner of the graph. LABEL CREATE LABEL The synopsis of both VLABEL and ELABEL is identical. CREATE [ UNLOGGED ] VLABEL [ IF NOT EXISTS ] label_name [DISABLE INDEX] [ INHERITS ( parent_label_name [, ...] ) ] [ WITH (storage_parameter)] [ TABLESPACE tablespace_name ]; 16 AgensGraph Quick Guide • UNLOGGED – Data written to an unlogged label is not recorded to the write-ahead log, which makes unlogged labels considerably faster than logged labels. However, unlogged labels are not crash-safe. • IF NOT EXISTS – Do nothing if the same name already exists. • label_name – The name of the vertex/edge label to be created. • DISABLE INDEX – Create label with invalid index. The invalid indexes can not be used for searching or inserting until reindexed. • INHERITS ( parent_label [, …] ) – The optional INHERITS clause speci ies a list of vertex/edge labels. If it is empty, the new label inherits the initial label. Use of INHERITS creates a persistent edge between the new child label and its parent label(s). The data of the child label is included in scans of the parent(s) by default. • TABLESPACE tablespace_name – The new label will be created in the tablespace whose name is tablespace_name. ALTER LABEL ALTER [ IF EXISTS ] VLABEL label_name RENAME TO new_name; ALTER [ IF EXISTS ] VLABEL label_name OWNER TO new_owner; ALTER [ IF EXISTS ] VLABEL label_name SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }; ALTER [ IF EXISTS ] VLABEL label_name SET TABLESPACE new_tablespace; ALTER [ IF EXISTS ] VLABEL label_name CLUSTER ON idxname; ALTER [ IF EXISTS ] VLABEL label_name SET WITHOUT CLUSTER; ALTER [ IF EXISTS ] VLABEL label_name SET LOGGED; ALTER [ IF EXISTS ] VLABEL label_name SET UNLOGGED; ALTER [ IF EXISTS ] VLABEL label_name INHERIT parent_label; ALTER [ IF EXISTS ] VLABEL label_name NO INHERIT parent_label; ALTER [ IF EXISTS ] VLABEL label_name DISABLE INDEX; • IF EXISTS – Do not throw an error if the label does not exist. Data Model 17 • label_name – The name of an existing vertex/edge label. • RENAME TO new_name – Changes the name of a label to new_name. • OWNER TO new_owner – Changes the owner of the label. • SET STORAGE – This form sets the storage mode for property. This controls whether property is held inline or in a secondary TOAST table, and whether the data should be compressed or not. – PLAIN must be used for ixed-length, inline and uncompressed values. – MAIN is inline and compressed. – EXTERNAL is external and uncompressed. – EXTENDED is external and compressed. • SET TABLESPACE – This form changes the label's tablespace to the speci ied tablespace and moves the data iles to the new tablespace. Indexes on the label are not moved. • CLUSTER/WITHOUT CLUSTER – This form select/remove the default index for future cluster operation. See this. • SET LOGGED/UNLOGGED – This form changes the label from unlogged to logged or vice-versa. • INHERIT/NO INHERIT – This form adds/removes the target label to/from the parent label's children list. • DISABLE INDEX – This form changes all indexes of the label to invalid index. The invalid indexes can not be used for searching or inserting until reindexed. Property Index The property index provides a method to build indexes on the property values. Users can also create an index for an expression. CREATE INDEX 18 AgensGraph Quick Guide CREATE [UNIQUE] PROPERTY INDEX [CONCURRENTLY] [IF NOT EXIST] indexname ON labelname [USING method] ( attribute_expr | (expr) [COLLATE collation] [opclass] [ASC | DESC] [NULLS {FIRST | LAST}] ) [WITH] (storage_parameter = value [,...]) [TABLESPACE tablespacename] [WHERE predicate]; • UNIQUE – Causes the system to check for duplicate values in the table when the index is created if the data already exists and each time data is added. Attempts to insert or update data which would result in duplicate entries will generate an error. • CONCURRENTLY – With this option, the index will be built without taking any locks that prevent concurrent CREATE, DELETE(DETACH), SET on the label. There are several caveats to be aware of when using this option. See this. • IF NOT EXIST – Do nothing if the same name already exists • indexname – The name of the index to be created. If it is omitted, AgensGraph chooses an adequate name. • labelname – The name of the label to be indexed. • USING METHOD – The name of the index method to be used. They are btree, hash, gist, spgist, gin and brin. The default method is btree. • attribute_expr – An expression which is pointing the attribute of property. • COLLATE collation – The name of the collation to use for the index. By default, the index uses the collation declared for the column to be indexed or the result collation of the expression to be indexed. Indexes with non-default collations can be useful for queries that involve expressions using non-default collations. Data Model 19 • opclass – The name of an operator class. • ASC | DESC – Speci ied ascending/descending sort order. ASC is the default. • NULLS { FIRST | LAST } – Speci ies that nulls sort before/after non-nulls. LAST is default when ASC is speci ied. • WITH storage_parameter – The name of an index-method-speci ic storage parameter. See Index Storage Parameters for details. • TABLESPACE tablespacename – The tablespace in which to create the index. • WHERE predicate – The constraint expression for a partial index. DROP INDEX DROP PROPERTY INDEX indexname [CASCADE | RESTRICT]; • indexname – The indexname can be checked with ag_property_indexes or \dGi. • CASCADE – Automatically drop objects that depend on the graph. • RESTRICT – Refuse to drop the index if any objects depend on it. This is the default. Constraints This section provides information about how to use constraints on properties. Users can create two types of constraints; UNIQUE constraint and CHECK constraint. CREATE CONSTRAINT constraint_name ON label_name ASSERT field_expr IS UNIQUE; CREATE CONSTRAINT constraint_name ON label_name ASSERT check_expr; DROP CONSTRAINT constraint_name ON label_name; • ield_expr 20 AgensGraph Quick Guide – This form represents a JSON expression. This JSON can be a nested JSON. • UNIQUE – This form speci ied that json_expression can contain only unique values. • check_expr – The check expression returns a boolean result for new or updated properties. The result must be TRUE or UNKNOWN for an insert or update to succeed. Should any property of an insert or update operation produce a FALSE result, an error exception is raised and the insert or update will rolled back. Data Model 21 5 AgensGraph Query 5.1 Graph Query 5.1.1 Introduction To retrieve and manipulate graph data, AgensGraph supports the Cypher query language. Cypher is a declarative language similar to SQL. Cypher is easy to learn since its syntax visually describes the patterns found in graphs. This guide brie ly explains how to write Cypher queries using an example graph. 5.1.2 Creating an Example Graph AgensGraph can store multiple graphs in a single database. However, Cypher has no way of discerning multiple graphs. Therefore, AgensGraph supports additional Data De inition Languages and variables to create and manage graphs using Cypher. The following statements create a graph called network and set it as a current graph. CREATE GRAPH network; SET graph_path = network; In this example, the graph_path variable is explicitly set to network. However, if graph_path is not set before creating the graph, it will be set automatically after creating the graph. Creating the Labels Before creating graph data, generating a label is basic. Although this is the default, label is generated automatically when you specify label in the CREATE statement in cypher(VLABEL/ELABEL can both be created). note: Be careful not to confuse the label with the lable. Unintentional new labels can be created. All graph elements have one label. For vertex, if no label is speci ied, have ag_vertex as a default label. For edge, the label can not be omitted. ag_edge label also exists but is used for other purposes. AgensGraph supports DDL's to create such labels. The following statements create a vertex label person and a edge label knows. CREATE VLABEL person; CREATE ELABEL knows; CREATE (n:movie {title:'Matrix'}); 22 AgensGraph Quick Guide Creating the Vertices and Edges Now, we can create vertices for person and edges for knows by using Cypher's CREATE clause. The CREATE clause creates a pattern that consists of vertices and edges. A vertex has the form: (variable:label {property: value, ...}), and a edge has: -[variable:label {property: value, ...}]-. An additional < on the leftmost side or > on the rightmost side is used to denote the direction of the edge. variable can be omitted if created vertices and edges are not to be referenced. note: AgensGraph does not support -- grammar for an edge in a pattern because -- means a comment to the end of the line. The following statements create three simple patterns: ``Tom knows Summer'', ``Pat knows Nikki'' and ``Olive knows Todd''. CREATE (:person {name: 'Tom'})-[:knows {fromdate:'2011-11-24'}]->(:person {name: 'Summer'}); CREATE (:person {name: 'Pat'})-[:knows {fromdate:'2013-12-25'}]->(:person {name: 'Nikki'}); CREATE (:person {name: 'Olive'})-[:knows {fromdate:'2015-01-26'}]->(:person {name: 'Todd'}); MATCH (p:Person {name: 'Tom'}),(k:Person{name: 'Pat'}) CREATE (p)-[:KNOWS {fromdate:'2017-02-27'} ]->(k); To store properties of vertices and edges, AgensGraph uses PostgreSQL's jsonb type. Properties can have nested JSON objects as their values. Since AgensGraph uses PostgreSQL's type system, any data type supported by PostgreSQL can be stored into the properties of vertices and edges. 5.1.3 Querying the Graph Let's retrieve the pattern we created above. Cypher has the MATCH clause to ind a pattern in a graph. The following statement inds the pattern, ``A person called Tom knows a person''. MATCH (n:person {name: 'Tom'})-[:knows]->(m:person) RETURN n.name AS n, m.name AS m; n | m -------+---------"Tom" | "Summer" "Tom" | "Pat" (2 rows) Since properties are of the jsonb type, we need methods to access their property values. PostgreSQL supports those methods through operators such as ->, ->>, #>, and #>>. If a user wants to access to the property name of vertex m, one can write (m)->>name. AgensGraph offers an alternate way to access these elements. AgensGraph uses the dot AgensGraph Query 23 operator . and bracket operators [] on vertices and edges to access property values in JSON objects and elements in JSON arrays as shown above. The RETURN clause returns variables and its properties as a result of the query. The result is a table which has multiple matched patterns in its rows. Variable Length Edges Let's consider a query that inds knows of `Tom' and knows of knows. We can use the UNION clause: MATCH (p:person {name: 'Tom'})-[:knows]->(f:person) RETURN f.name UNION ALL MATCH (p:person {name: 'Tom'})-[:knows]->()-[:knows]->(f:person) RETURN f.name; It can also be written as: MATCH (p:person {name: 'Tom'})-[r:knows*1..2]->(f:person) RETURN f.name, r[1].fromdate; A query looking for vertices located after a variable length of edge-vertex paths is typical in graph databases. *1..2 used in the edge represents such a variable-length edge. Where 1 is the minimum length of the edge and 2 is the maximum length. If you do not specify a value, the default range values are 1 and in inity. You can also use update clauses such as CREATE, SET, REMOVE and DELETE after MATCH clauses. In the next section, we will see how data in a graph can be modi ied and deleted. 5.1.4 Manipulating the Graph You can set properties on vertices and edges using the SET clause. If you set a null value to a property, the property will be removed. The following statement inds the given pattern and updates the property in the matched edge. MATCH (:person {name: 'Tom'})-[r:knows]->(:person {name: 'Summer'}) SET r.since = '2009-01-08'; To delete vertices and edges in a graph, we can use the DELETE clause. The following statement inds a vertex and deletes it. MATCH (n:person {name: 'Pat'}) DETACH DELETE (n); The above example actually uses the DETACH DELETE clause to delete vertices and edges attached to the vertices all at once. 24 AgensGraph Quick Guide The inal shape of the graph network is as follows: MATCH (n)-[r]->(m) RETURN n.name AS n, properties(r) AS r, m.name AS m; n | r | m ---------+---------------------------------------------------+---------"Tom" | {"since": "2009-01-08", "fromdate": "2011-11-24"} | "Summer" "Olive" | {"fromdate": "2015-01-26"} | "Todd" (2 rows) 5.1.5 MERGE If you need to ensure that a pattern exists in the graph, you can use MERGE. It will try to ind the pattern if the pattern exists in the graph, or else it creates the pattern if it does not exist. If the pattern exists, it is treated like a MATCH clause, otherwise it is treated like a CREATE clause. MERGE is a MATCH or CREATE of the entire pattern. This means that if any element of the pattern does NOT exist, AgensGraph will create the entire pattern. The following statement guarantees that everyone's city exists in the graph. CREATE VLABEL customer; CREATE VLABEL city; CREATE (:customer {name:'Tom', city:'santa clara'}), (:customer {name:'Summer ', city:'san jose'}), (:customer {name:'Pat', city:'santa clara'}), (:customer {name:'Nikki', city:'san jose'}), (:customer {name:'Olive', city:'san francisco'}); MATCH (a:customer) MERGE (c:city {name:a.city}); MATCH (c:city) RETURN properties(c); properties ------------------------{"name": "santa clara"} {"name": "san jose"} {"name": "san francisco"} (3 rows) AgensGraph Query 25 MERGE can perform SET depending on whether the pattern is MATCHed or CREATed. If it is MATCHed, it will execute ON MATCH SET clause. If it is CREATE-ed, it will execute ON CREATE SET clause. CREATE (:customer {name:'Todd', city:'palo alto'}); MATCH (a:customer) MERGE (c:city {name:a.city}) ON MATCH SET c.matched = 'true' ON CREATE SET c.created = 'true'; MATCH (c:city) RETURN properties(c); properties ---------------------------------------------{"name": "santa clara", "matched": "true"} {"name": "san jose", "matched": "true"} {"name": "san francisco", "matched": "true"} {"name": "palo alto", "created": "true"} (4 rows) The default isolation level of the transaction is Read committed on AgensGraph. Therefore, if another transaction executes MERGE for the same pattern at the same time, two (or more) identical patterns can be created at the same time. To prevent this, you can execute a transaction at the serializable isolation level as in the example below. If an attempt is made to create the same pattern concurrently, one transaction fails with an error. If you retry a failed transaction, it will behave like MATCH instead of CREATE because of the pattern created by the succeeded transaction already exists. BEGIN; SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; MATCH (a:customer) MERGE (c:city {name:a.city}); COMMIT; 5.1.6 Finding the Shortest Path The shortestpath function can be used to ind the shortest path between two vertices. If you want to ind all paths, you can use the allshortestpaths function. 26 AgensGraph Quick Guide MATCH (p:person {name:'Tom'}), (f:person {name:'Olive'}) CREATE (p)-[:knows]->(f); MATCH (p1:person {name: 'Tom'}), (p2:person {name: 'Todd'}), path=shortestpath((p1)-[:knows*1..5]->(p2)) RETURN path; In this example, we create a `knows' edge path from `Tom' to `Pat'. To ind the `knows' path from `Tom' to `Nikki', we can use the shortestpath function. The shortestpath function takes a pattern consisting of a start vertex, a edge and an end vertex. We can use a variable length edge expression in the edge to specify if we are looking for a certain degree of connection. The query results are as follows. [person[3.1]{"name": "Tom"},knows[4.5][3.1,3.5]{},person[3.5]{"name": "Olive"},knows[4.3][3.5,3.6] {"fromdate": "2015-01-26"},person[3.6]{"name": "Todd"}] 5.2 Hybrid Query 5.2.1 Introduction In this section, we will see how to use SQL and Cypher together in AgensGraph using the following example graph. Hybrid Query performs aggregation and statistical processing on table and column by using SQL query used in RDB,and the Cypher query used by GDB supports better data query than RDB's Join operation. CREATE GRAPH bitnine; CREATE VLABEL dev; CREATE (:dev {name: 'someone', year: 2015}); CREATE (:dev {name: 'somebody', year: 2016}); CREATE TABLE history (year, event) AS VALUES (1996, 'PostgreSQL'), (2016, 'AgensGraph'); Cypher in SQL Since the result of a Cypher query is a relation, you can use a Cypher query in the FROM clause of SQL as if it is a subquery. It is possible to use Cypher syntax inside the FROM clause to utilize dataset of vertex or edge stored in graph DB as data in SQL statement. Syntex : AgensGraph Query 27 SELECT [column_name] FROM ({table_name|SQLquery|CYPHERquery}) WHERE [column_name operator value]; Example : SELECT n->>'name' as name FROM history, (MATCH (n:dev) RETURN n) as dev where history.year > (n->>'year')::int; name --------someone (1 row) SQL in Cypher When querying the content of the graph DB with the cypher queries, you can use the match and where clause when you want to search using speci ic data of the RDB. However, the resulting dataset in the SQL queries must be con igured to return a single row of results. Syntex : MATCH [table_name] WHERE (column_name operator {value|SQLquery|CYPHERquery}) RETURN [column_name]; Example : MATCH (n:dev) WHERE n.year < to_jsonb((SELECT year FROM history WHERE event = 'AgensGraph')) RETURN properties(n) AS n; n ----------------------------------{"name": "someone", "year": 2015} (1 row) 28 AgensGraph Quick Guide 6 Graph Data Import This section introduces an example to import graph data from external foreign iles. 1. Install the extension ` ile_fdw' necessary to use the AgensGraph foreign-data wrapper to interface with iles on the server's ilesystem. CREATE EXTENSION file_fdw; 2. Create the data import server. CREATE SERVER import_server FOREIGN DATA WRAPPER file_fdw; 3. Create the foreign table to receive data from a foreign ile. CREATE FOREIGN TABLE vlabel_profile (id graphid, properties text) SERVER import_server OPTIONS( FORMAT 'csv', HEADER 'false', FILENAME '/path/file.csv', delimiter E'\t'); CREATE FOREIGN TABLE elabel_profile (id graphid, start graphid, "end" graphid, properties text) SERVER import_server OPTIONS( FORMAT 'csv', HEADER 'false', FILENAME '/path/file.csv', delimiter E'\t'); This `properties text' item should be written differently depending on the situation. See the following example. comments.csv id|creationDate|locationIP|browserUsed|content|length // This is the HEADER of CSV 2473901162497|1316237219961|77.240.75.197|Firefox|yes|3 2473901162498|1316225421570|213.180.31.8|Firefox|thanks|6 4123168604165|1345407771283|41.203.141.129|Firefox|LOL|3 In this case, the schema of foreign table should be as follows. create foreign table comments_profile ( id int8, creationDate int8, locationIP varchar(80), Graph Data Import 29 browserUsed varchar(80), content varchar(2000), length int4 ) server import_server options ( FORMAT 'csv', HEADER 'true', //Indicates the presence of a csv header DELIMITER '|', NULL '', FILENAME '/path/to/comments.csv' ); 4. Execute the import. The data must be cast as type JSONB, since vertices and edges in AgensGraph are stored in the JSONB format. CREATE VLABEL test_vlabel; LOAD FROM vlabel_profile AS profile_name CREATE (a:test_vlabel =to_jsonb(row_to_json(profile_name))); CREATE ELABEL test_elabel; LOAD FROM elabel_profile AS profile_name MATCH (a:test_vlabel), (b:test_vlabel) WHERE (a).id = to_jsonb(profile_name).start AND (b).id = to_jsonb(profile_name).end CREATE (a)-[:test_elabel]->(b); Following the example above, you can do the following: CREATE VLABEL comments; LOAD FROM comments_profile AS ROW CREATE (:comments =to_jsonb(row_to_json(row))); 30 AgensGraph Quick Guide 6.0.1 Indexes with Data Import The cost of maintaining indexes during bulk insertion is very expensive. AgensGraph provides grammars to toggle indexes by disabling them temporarily and reindexing them later. The disabled indexes do not interfere with bulk inserts. After bulk data import, the option REINDEX LABEL can be used. It will take some time but it is much faster than bulk insert with valid indexes. CREATE VLABEL test_vlabel DISABLE INDEX; OR CREATE VLABEL test_vlabel; ALTER VLABEL test_vlabel DISABLE INDEX; -- DATA IMPORT REINDEX VLABEL test_vlabel; Graph Data Import 31 7 Tools 7.1 Command Line Interface Tool AgensGraph has a command line interface tool called agens. Users can query and maintain AgensGraph using agens ef iciently. Note: agens is based on psql (the PostgreSQL interactive command line tool) so that all features of psql can be used in AgensGraph too. 7.1.1 Meta Command \dG[+] [PATTERN] list graphs \dGe[+] [PATTERN] list graph edge labels \dGl[+] [PATTERN] list graph labels \dGv[+] [PATTERN] list graph vertex labels \dGi[+] [PATTERN] list graph property indexes agens supports the above additional meta-commands for administration and scripting. You can obtain a list of graph or labels. If + is appended to the command, each object is listed with its associated permissions and description, if any. If pattern is speci ied, only objects whose name match the pattern are listed. 32 AgensGraph Quick Guide 8 Client Drivers 8.1 Java Driver 8.1.1 Introduction This section brie ly explains how to process graph data through AgensGraph to Java application developers. AgensGraph's JDBC driver is based on the PostgreSQL JDBC Driver and offers a way for the Java application developer to access the Agensgraph database in their applications. The API of the AgensGraph Java Driver and Postgres JDBC Driver are very similar. The only difference is that AgensGraph uses the Cypher query language instead of SQL and utilizes graph data (vertices, edges and paths) as data types. 8.1.2 Usage of the Java Driver Get the Driver You can download the precompiled driver(jar) from Download link or use maven as follows: ... You can search the latest version on The Central Repository with Groupld and Artifactld. Connection To connect to AgensGraph using the Java Driver, we need two things: the name of class to be loaded into the Java Driver and the connection string. • The name of class is net.bitnine.agensgraph.Driver. • The connection string consists of the sub-protocol, server, port, database. Client Drivers 33 • jdbc:agensgraph://is the sub-protocol to use a particular Driver and a hold value. • It is written as jdbc:agensgraph://server:port/database, including the sub-protocol. The following code is an example of how to connect AgensGraph. It connects to AgensGraph through the Connection object and is ready to be queried. import java.sql.DriverManager; import java.sql.Connection; public class AgensGraphTest { public static void main(String[] args) { try{ Class.forName("net.bitnine.agensgraph.Driver"); String connectionString = "jdbc:agensgraph://127.0.0.1:5432/agens"; String username = "test"; String password = "test"; Connection conn = DriverManager.getConnection(connectionString, username, password); ... } catch (Exception e) { e.printStackTrace(); } } } Retrieving Data This example illustrates how to export Graph data using MATCH. A Cypher query is executed using executeQuery(). The output is a ResultSet object, which is the same output format found in the JDBC driver. The output of the query is the `vertex' type of AgensGraph. Java Driver returns this output as a Vertex instance. Because the Vertex class is a sub-class of Jsonb, users can obtain information from the property ields. import java.sql.DriverManager; import java.sql.Connection; import java.sql.Statement; import java.sql.ResultSet; 34 AgensGraph Quick Guide import net.bitnine.agensgraph.graph.Vertex; public class AgensGraphTest { public static void main(String[] args) { try{ ... Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery( "MATCH (:Person {name: 'John'})-[:knows]-(friend:Person)" + "RETURN friend"); while (rs.next()) { Vertex friend = (Vertex)rs.getObject(1); System.out.println(friend.getString("name")); System.out.println(friend.getInt("age")); } catch (Exception e) { e.printStackTrace(); } } } } Creating Data The following example illustrates how to insert a vertex with a label Person into AgensGraph. Users can input a property of a vertex using strings in Cypher queries. They can also be bound after making a Jsonb. import java.sql.DriverManager; import java.sql.Connection; import java.sql.PreparedStatement; import net.bitnine.agensgraph.util.Jsonb; import net.bitnine.agensgraph.util.JsonbUtil; public class AgensGraphTest { public static void main(String[] args) { Client Drivers 35 ... PreparedStatement pstmt = conn.prepareStatement("CREATE (:person ?)"); Jsonb john = JsonbUtil.createObjectBuilder() .add("name", "John") .add("from", "USA") .add("age", 17) .build(); pstmt.setObject(1, john); pstmt.execute(); } } The following is generated as a string: "CREATE (:Person {name: 'John', from: 'USA', age: 17})" [Reference] In JDBC, the question mark (?) is the placeholder for the positional parameters of a PreparedStatement. There are, however, a number of SQL operators that contain a question mark. To avoid confusion, when used in a prepared statement, it must be used with spaces. 36 AgensGraph Quick Guide 9 External Modules 9.1 External Modules 9.1.1 Introduction This section brie ly explains external modules which are contained in AgensGraph. One of great things of AgensGraph is that there are plenty of great external modules. Any PostgreSQL external modules can be used in AgensGraph too. The external modules which are provided by AgensGraph will be maintained with version upgrades. Usually, these modules have to be set correctly. You can refer to the documentations provided by each external module. 9.1.2 Server Monitoring: pg_stats_info Users can monitor AgensGraph using pg_stats_info. You can also use Tadpole for AgensGraph (http://bitnine.net/ downloads/tadpole-agensgraph/) for real-time monitoring. 9.1.3 Plan Optimization: pg_hint_plan Using pg_hint_plan, users can modify query plans to optimize the performance. pg_hint_plan can be used to Cypher plans. 9.1.4 Warm Cache: pg_prewarm By loading graph objects (vertex, edge and indexes), one can obtain the best performace. Using pg_prewarm, users can specify graph objects to be loaded in memory. 9.1.5 Statistics: hyperloglog Hyperloglog can be used to estimate the count of distinct values in tables. 9.1.6 Big Data: hadoopfdw Using Hadoopfdw and LOAD clause, users can load data from external hadoop systems to AgensGraph graph object. External Modules 37... net.bitnine agensgraph-jdbc 1.4.1
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