问题描述
我正在创建一个Databricks应用程序,并且数据库架构变得不平凡。有没有一种方法可以为Databricks数据库生成架构图(类似于可以从mysql生成的架构图)?
解决方法
可能有2种变体:
- 将Spark SQL与
show databases
,show tables in <database>
,describe table ...
一起使用 - 使用
spark.catalog.listDatabases
,spark.catalog.listTables
,spark.catagog.listColumns
。
2nd变体的性能不是很好,尽管通过编程使用它稍微容易一些。但是在这两种情况下,实现都是3个嵌套循环,依次遍历数据库列表,数据库内部表列表和表内部列列表。可以使用您喜欢的图表工具将这些数据用于生成图表。
以下是生成PlantUML的源代码:
# This script generates PlantUML diagram for tables visible to Spark.
# The diagram is stored in the db_schema.puml file,so just run
# 'java -jar plantuml.jar db_schema.puml' to get PNG file
from pyspark.sql import SparkSession
from pyspark.sql.utils import AnalysisException
# Variables
# list of databases/namespaces to analyze. Could be empty,then all existing
# databases/namespaces will be processed
databases = ["a","airbnb"] # put databases/namespace to handle
# change this if you want to include temporary tables as well
include_temp = False
# implementation
spark = SparkSession.builder.appName("Database Schema Generator").getOrCreate()
# if databases aren't specified,then fetch list from the Spark
if len(databases) == 0:
databases = [db["namespace"] for db in spark.sql("show databases").collect()]
with open(f"db_schema.puml","w") as f:
f.write("\n".join(
["@startuml","skinparam packageStyle rectangle","hide circle","hide empty methods","",""]))
for database_name in databases[:3]:
f.write(f'package "{database_name}" {{\n')
tables = spark.sql(f"show tables in `{database_name}`")
for tbl in tables.collect():
table_name = tbl["tableName"]
db = tbl["database"]
if include_temp or not tbl["isTemporary"]:
lines = []
try:
lines.append(f'class {table_name} {{')
cols = spark.sql(f"describe table `{db}`.`{table_name}`")
for cl in cols.collect():
col_name = cl["col_name"]
data_type = cl["data_type"]
lines.append(f'{{field}} {col_name} : {data_type}')
lines.append('}\n')
f.write("\n".join(lines))
except AnalysisException as ex:
print(f"Error when trying to describe {tbl.database}.{table_name}: {ex}")
f.write("}\n\n")
f.write("@enduml\n")
然后可以将其转换为图片: