Source code for langchain.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:
    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,
    ):
        try:
            from pyspark.sql import SparkSession
        except ImportError:
            raise ValueError(
                "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"
                )
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 ValueError(
                "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"{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.
If the statement throws an error, the error message is returned.
        """
        try:
            from pyspark.errors import PySparkException
        except ImportError:
            raise ValueError(
                "pyspark is not installed. Please install it with `pip install pyspark`"
            )
        try:
            return self.run(command, fetch)
        except PySparkException as e:
            """Format the error message"""
            return f"Error: {e}"
By Harrison Chase