xingyuan cheng created CALCITE-6171:
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Summary: Support gremlin adapter
Key: CALCITE-6171
URL: https://issues.apache.org/jira/browse/CALCITE-6171
Project: Calcite
Issue Type: New Feature
Affects Versions: 1.36.0
Reporter: xingyuan cheng
Motivation
Hi, community. Currently, more and more users are using some graph databases,
such as JanusGraph, HugeGraph, etc.
To do some relationship representation of personnel social networks,
It is used to count the activity of each user in the social network. Most graph
databases are in the graph building and graph traversal stage.
All will be implemented using Gremlin syntax.
However, this is very unfriendly to users who are not familiar with gremlin
syntax. While calcite exists as a query framework,
It also provides an adapter interface to adapt to different database dialects,
such as parsing, relational algebra conversion, and query plan binding.
Our company has solved the problem of adapting various graph databases. This is
my warehouse: https://github.com/kaori-seasons/calcite-gremlin-sql
Background
Calcite itself supports the database language expansion of the adapter, which
enables users to understand the meaning of the grammar.
Complete the simplification of the dialect. For example, expand SqlNode to
implement syntax analysis, and expand RelNode to implement logical plan mapping.
thinkerpop is an adaptation framework for various graph databases. In this
framework, gremlin syntax is mentioned for the first time.
It has now become a universal query layer for graph databases. While expanding
query statements through calcite’s adapter interface,
We will also use thinkerpop's universal graph database API to provide dialect
compatibility for different graph databases.
Give a simple example:
>From SELECT "key" FROM inttype maps to
g.V().hasLabel("inttype").group().unfold().select(Column.values).order().by(__.unfold().id()).project("inttype").
by(__.project("key").by(__.unfold().choose(__.has("key"),__.values("key"),__.constant("\$%#NULL#
%\$"))))
The design architecture is divided into three layers.
Analytical syntax layer, relational algebra transformation layer, logical plan
binding layer.
Parsing syntax layer: In the parsing query statement phase, fields and
equivalent conditions are split and converted into points and edges.
Relational algebra layer: Split it into a collection of points and edges, and
convert it into a TableScan during the aggregation/sorting/query stage where
calcite abstracts it.
It is convenient to generate query plans based on conditions and field
information.
Connection scanning/single table filtering and other methods can be used to
traverse from any edge/any starting point in the graph
Logical plan binding layer: Bind behaviors such as connection scanning/single
table filtering/projection to calcite’s planner to generate query plans.
The process of generating Gremlin logical plan using select statement:
1. First of all, all graph databases start from a source point to build the
graph. We will use the GraphTraversalSource provided by thinkerpop.
As the origin, extract the syntax of the incoming point and side information.
This step will be implemented in SqlSchemaGrabber
2. Secondly, for select/where/having/order by/group by our plan in the parsing
phase is as follows:
- group by: for a point. There are out-degree and in-degree attributes in the
graph. From the perspective of the data table, it is equivalent to converting
the table data into IN or OUT.
These two dimensions are aggregated. This behavior also corresponds to the
table traversal graph operation. During the graph traversal process,
fold/unfold tags will be generated, representing the direction of graph
traversal.
- select: For the select operation, the operation of scanning the entire
table can be regarded as projecting all columns into point attributes. The
value changes of each column are mapped to the gremlin operation of adding
points.
- where: The filter operation is used in graph computing semantic scenarios.
It can be regarded as the edges connected by the out-degree and in-degree of
the filter point, so it does not involve the conversion of relational algebra.
Instead, it is pushed directly to the logical plan.
- order by: In the process of graph traversal, we mentioned that fold/unflod
will be generated on the path to represent the forward/backward direction.
If a field is encountered and there is no value that can be sorted, we will
fall back to the origin of GraphTraversalSource and end the sorting operation.
If there are values that can be sorted, they will be unified in
SqlTraversalEngine, in-degree and out-degree will be counted separately for
aggregation, and then used with group by according to label (IN/OUT)
- having: The meaning is the same as group by, but the label is different (in
addition to the IN/OUT columns, specific point fields need to be specified)
samples(samples)
Below I will give a simple example using the unit test in my project
Now suppose there is such a graph data set, there are multiple point sets 🎁 and
an edge set
Since the company is connected to the graph database, further testing is
needed. I will complete it in the near future //todo
The point sets respectively represent countries, companies, groups of people,
and spatial locations.
{
"tables": [
{
"name": "company",
"columns": [
\{"name": "name", "type": "string"}
]
},
{
"name": "country",
"columns": [
\{"name": "name", "type": "string"}
]
},
{
"name": "planet",
"columns": [
\{"name": "name", "type": "string"}
]
},
{
"name": "person",
"columns": [
\{"name": "name", "type": "string"},
\{"name": "age", "type": "integer"}
]
},
{
"name": "spaceship",
"columns": [
\{"name": "name", "type": "string"},
\{"name": "model", "type": "string"}
]
},
{
"name": "satellite",
"columns": [
\{"name": "name", "type": "string"}
]
},
{
"name": "sensor",
"columns": [
\{"name": "name", "type": "string"},
\{"name": "type", "type": "string"}
]
},
{
"name": "sensorReading",
"columns": [
\{"name": "tstamp", "type": "long_timestamp", "propertyName":
"timestamp"},
\{"name": "dt", "type": "long_date", "propertyName": "date"},
\{"name": "value", "type": "double"}
]
},
{
"name": "fliesTo",
"columns":[
\{"name": "trips", "type": "integer"}
]
},
{
"name": "orbits",
"columns":[
\{"name": "launched", "type": "integer"}
]
}
],
"relationships": [
\{"outTable": "company", "inTable": "country", "edgeLabel": "baseIn"},
\{"outTable": "person", "inTable": "company", "edgeLabel": "worksFor"},
\{"outTable": "person", "inTable": "planets", "edgeLabel": "travelledTo"},
\{"outTable": "company", "inTable": "spaceship", "edgeLabel": "owns"},
\{"outTable": "person", "inTable": "spaceship", "edgeLabel": "pilots"},
\{"outTable": "sensor", "inTable": "sensorReading", "edgeLabel":
"hasReading", "fkTable": "sensorReading"},
\{"outTable": "person", "inTable": "planet", "edgeLabel": "fliesTo"},
\{"outTable": "satellite", "inTable": "planet", "edgeLabel": "orbits"},
\{"outTable": "person", "inTable": "person", "edgeLabel": "friendsWith"}
]
}
Scope of application
Graph database compatible with thinkerpop's gremlin syntax
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