ekuiper-new/docs/en_US/rules/sources/plugin/sql.md

Sql Source

stream source scan table source lookup table source

The source will query the database periodically to get data stream.

Compile & deploy plugin

This plugin must be used in conjunction with at least a database driver. We are using build tag to determine which driver will be included. This repository lists all the supported drivers.

This plugin supports sqlserver\postgres\mysql\sqlite3\oracle drivers by default. User can compile plugin that only support one driver by himself, for example, if he only wants sqlserver, then he can build with build tag sqlserver.

Default build command

# cd $eKuiper_src
# go build -trimpath -modfile extensions.mod --buildmode=plugin -o plugins/sources/Sql.so extensions/sources/sql/*.go
# cp plugins/sources/Sql.so $eKuiper_install/plugins/sources

Sqlserver build command

# cd $eKuiper_src
# go build -trimpath -modfile extensions.mod --buildmode=plugin -tags sqlserver -o plugins/sources/Sql.so extensions/sources/sql/*.go
# cp plugins/sources/Sql.so $eKuiper_install/plugins/sources

Restart the eKuiper server to activate the plugin.

Configuration

The configuration for this source is $ekuiper/etc/sources/sql.yaml. The format is as below:

default:
  interval: 10000
  url: mysql://user:test@140.210.204.147/user?parseTime=true
  internalSqlQueryCfg:
    table: test
    limit: 1
    indexField: registerTime
    indexValue: "2022-04-21 10:23:55"
    indexFieldType: "DATETIME"
    dateTimeFormat: "YYYY-MM-dd HH:mm:ss"

sqlserver_config:
  url: sqlserver://username:password@140.210.204.147/testdb
  internalSqlQueryCfg:
    table: Student
    limit: 10
    indexField: id
    indexValue: 1000

template_config:
  templateSqlQueryCfg:
    TemplateSql: "select * from table where entry_data > {{.entry_data}}"
    indexField: entry_data
    indexValue: "2022-04-13 06:22:32.233"
    indexFieldType: "DATETIME"
    dateTimeFormat: "YYYY-MM-dd HH:mm:ssSSS"

Global configurations

User can specify the global sql source settings here. The configuration items specified in default section will be taken as default settings for the source when running this source.

interval

The interval (ms) to issue a query.

url

The target database url

database	url sample
mysql	mysql://user:test@140.210.204.147/user?parseTime=true
sql server	sqlserver://username:password@140.210.204.147/testdb
postgres	postgres://user:pass@localhost/dbname
postgres	postgres://user:pass@localhost/dbname
sqlite	sqlite:/path/to/file.db

internalSqlQueryCfg

• table: table name to query
• limit: how many items need fetch from the result
• indexField: which column for the table act as index to record the offset
• indexValue: initial index value, if user specify this field, the query will use this initial value as query condition, will update next query when get a greater value.
  
• indexFieldType: column type for the indexField, if it is dateTime type, must set this field with DATETIME
• dateTimeFormat: data time format for the index field

table	limit	indexField	indexValue	indexFieldType	dateTimeFormat	sql query statement
Student	10					select * from Student limit 10
Student	10	stun	100			select * from Student where stun > 100 limit 10
Student	10	registerTime	"2022-04-21 10:23:55"	"DATETIME"	"YYYY-MM-dd HH:mm:ss"	select * from Student where registerTime > '2022-04-21 10:23:55' order by registerTime ASC limit 10

templateSqlQueryCfg

• TemplateSql: sql statement template
• indexField: which column for the table act as index to record the offset
• indexValue: initial index value, if user specify this field, the query will use this initial value as query condition, will update next query when get a greater value.
• indexFieldType: column type for the indexField, if it is dateTime type, must set this field with DATETIME
• dateTimeFormat: data time format for the index field

::: v-pre | TemplateSql | indexField | indexValue | indexFieldType | dateTimeFormat | sql query statement | | ------------------------------------------------------------------------------------------------- | ------------ | --------------------- | -------------- | --------------------- | --------------------------------------------------------------------------------------------------- | | select * from Student limit 10 | | | | | select * from Student limit 10 | | select * from Student where stun > {{.stun}} limit 10 | stun | 100 | | | select * from Student where stun > 100 limit 10 | | select * from Student where registerTime > '{{.registerTime}}' order by registerTime ASC limit 10 | registerTime | "2022-04-21 10:23:55" | "DATETIME" | "YYYY-MM-dd HH:mm:ss" | select * from Student where registerTime > '2022-04-21 10:23:55' order by registerTime ASC limit 10 | :::

Note: users only need set internalSqlQueryCfg or templateSqlQueryCfg, if both set, templateSqlQueryCfg will be used

Override the default settings

If you have a specific connection that need to overwrite the default settings, you can create a customized section. In the previous sample, we create a specific setting named with template_config. Then you can specify the configuration with option CONF_KEY when creating the stream definition (see stream specs for more info).

Sample usage

demo (
  ...
 ) WITH (DATASOURCE="demo", FORMAT="JSON", CONF_KEY="template_config", TYPE="sql");

The configuration keys "template_config" will be used.

Lookup Table

The SQL source supports to be a lookup table. We can use create table statement to create a SQL lookup table. It will bind to the physical SQL DB and query on demand.

CREATE TABLE alertTable() WITH (DATASOURCE="tableName", CONF_KEY="sqlite_config", TYPE="sql", KIND="lookup")

Lookup cache

Query external DB is supposed to be slower than in memory calculation. If the throughput is high, the lookup cache can be used to improve the performance.

If lookup cache is not enabled, so all the requests are sent to external database. When lookup cache is enabled, each lookup table instance will hold a cache. When querying, we will first look up the cache before sending to the external database.

The cache configuration lies in the sql.yaml.

  lookup:
    cache: true
    cacheTtl: 600
    cacheMissingKey: true

• cache: bool value to indicate whether to enable cache.
• cacheTtl: the time to live of the cache in seconds.
• cacheMissingKey: whether to cache nil value for a key.