Source code for langchain_community.utilities.spark_sql
from __future__ import annotations
from typing import TYPE_CHECKING, Any, Iterable, List, Optional
if TYPE_CHECKING:
from pyspark.sql import DataFrame, Row, SparkSession
[docs]class SparkSQL:
"""SparkSQL is a utility class for interacting with Spark SQL."""
[docs] def __init__(
self,
spark_session: Optional[SparkSession] = None,
catalog: Optional[str] = None,
schema: Optional[str] = None,
ignore_tables: Optional[List[str]] = None,
include_tables: Optional[List[str]] = None,
sample_rows_in_table_info: int = 3,
):
"""Initialize a SparkSQL object.
Args:
spark_session: A SparkSession object.
If not provided, one will be created.
catalog: The catalog to use.
If not provided, the default catalog will be used.
schema: The schema to use.
If not provided, the default schema will be used.
ignore_tables: A list of tables to ignore.
If not provided, all tables will be used.
include_tables: A list of tables to include.
If not provided, all tables will be used.
sample_rows_in_table_info: The number of rows to include in the table info.
Defaults to 3.
"""
try:
from pyspark.sql import SparkSession
except ImportError:
raise ImportError(
"pyspark is not installed. Please install it with `pip install pyspark`"
)
self._spark = (
spark_session if spark_session else SparkSession.builder.getOrCreate()
)
if catalog is not None:
self._spark.catalog.setCurrentCatalog(catalog)
if schema is not None:
self._spark.catalog.setCurrentDatabase(schema)
self._all_tables = set(self._get_all_table_names())
self._include_tables = set(include_tables) if include_tables else set()
if self._include_tables:
missing_tables = self._include_tables - self._all_tables
if missing_tables:
raise ValueError(
f"include_tables {missing_tables} not found in database"
)
self._ignore_tables = set(ignore_tables) if ignore_tables else set()
if self._ignore_tables:
missing_tables = self._ignore_tables - self._all_tables
if missing_tables:
raise ValueError(
f"ignore_tables {missing_tables} not found in database"
)
usable_tables = self.get_usable_table_names()
self._usable_tables = set(usable_tables) if usable_tables else self._all_tables
if not isinstance(sample_rows_in_table_info, int):
raise TypeError("sample_rows_in_table_info must be an integer")
self._sample_rows_in_table_info = sample_rows_in_table_info
[docs] @classmethod
def from_uri(
cls, database_uri: str, engine_args: Optional[dict] = None, **kwargs: Any
) -> SparkSQL:
"""Creating a remote Spark Session via Spark connect.
For example: SparkSQL.from_uri("sc://localhost:15002")
"""
try:
from pyspark.sql import SparkSession
except ImportError:
raise ImportError(
"pyspark is not installed. Please install it with `pip install pyspark`"
)
spark = SparkSession.builder.remote(database_uri).getOrCreate()
return cls(spark, **kwargs)
[docs] def get_usable_table_names(self) -> Iterable[str]:
"""Get names of tables available."""
if self._include_tables:
return self._include_tables
# sorting the result can help LLM understanding it.
return sorted(self._all_tables - self._ignore_tables)
def _get_all_table_names(self) -> Iterable[str]:
rows = self._spark.sql("SHOW TABLES").select("tableName").collect()
return list(map(lambda row: row.tableName, rows))
def _get_create_table_stmt(self, table: str) -> str:
statement = (
self._spark.sql(f"SHOW CREATE TABLE {table}").collect()[0].createtab_stmt
)
# Ignore the data source provider and options to reduce the number of tokens.
using_clause_index = statement.find("USING")
return statement[:using_clause_index] + ";"
[docs] def get_table_info(self, table_names: Optional[List[str]] = None) -> str:
all_table_names = self.get_usable_table_names()
if table_names is not None:
missing_tables = set(table_names).difference(all_table_names)
if missing_tables:
raise ValueError(f"table_names {missing_tables} not found in database")
all_table_names = table_names
tables = []
for table_name in all_table_names:
table_info = self._get_create_table_stmt(table_name)
if self._sample_rows_in_table_info:
table_info += "\n\n/*"
table_info += f"\n{self._get_sample_spark_rows(table_name)}\n"
table_info += "*/"
tables.append(table_info)
final_str = "\n\n".join(tables)
return final_str
def _get_sample_spark_rows(self, table: str) -> str:
query = f"SELECT * FROM {table} LIMIT {self._sample_rows_in_table_info}"
df = self._spark.sql(query)
columns_str = "\t".join(list(map(lambda f: f.name, df.schema.fields)))
try:
sample_rows = self._get_dataframe_results(df)
# save the sample rows in string format
sample_rows_str = "\n".join(["\t".join(row) for row in sample_rows])
except Exception:
sample_rows_str = ""
return (
f"{self._sample_rows_in_table_info} rows from {table} table:\n"
f"{columns_str}\n"
f"{sample_rows_str}"
)
def _convert_row_as_tuple(self, row: Row) -> tuple:
return tuple(map(str, row.asDict().values()))
def _get_dataframe_results(self, df: DataFrame) -> list:
return list(map(self._convert_row_as_tuple, df.collect()))
[docs] def run(self, command: str, fetch: str = "all") -> str:
df = self._spark.sql(command)
if fetch == "one":
df = df.limit(1)
return str(self._get_dataframe_results(df))
[docs] def get_table_info_no_throw(self, table_names: Optional[List[str]] = None) -> str:
"""Get information about specified tables.
Follows best practices as specified in: Rajkumar et al, 2022
(https://arxiv.org/abs/2204.00498)
If `sample_rows_in_table_info`, the specified number of sample rows will be
appended to each table description. This can increase performance as
demonstrated in the paper.
"""
try:
return self.get_table_info(table_names)
except ValueError as e:
"""Format the error message"""
return f"Error: {e}"
[docs] def run_no_throw(self, command: str, fetch: str = "all") -> str:
"""Execute a SQL command and return a string representing the results.
If the statement returns rows, a string of the results is returned.
If the statement returns no rows, an empty string is returned.
If the statement throws an error, the error message is returned.
"""
try:
return self.run(command, fetch)
except Exception as e:
"""Format the error message"""
return f"Error: {e}"
