DBI Source

A DataSource implementation for DBI database connections (SQLite, PostgreSQL, MySQL, etc.).

Details

This class wraps a DBI connection and provides SQL query execution against a specified table in the database.

Super class

querychat::DataSource -> DBISource

Methods

Public methods

• DBISource$new()

• DBISource$get_db_type()

• DBISource$get_schema()

• DBISource$execute_query()

• DBISource$test_query()

• DBISource$get_data()

• DBISource$cleanup()

• DBISource$clone()

---

Method new()

Create a new DBISource

Usage

DBISource$new(conn, table_name)

Arguments

conn

A DBI connection object

table_name

Name of the table in the database. Can be a character string or a DBI::Id() object for tables in catalogs/schemas

Returns

A new DBISource object

Examples

\dontrun{
conn <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
DBI::dbWriteTable(conn, "iris", iris)
source <- DBISource$new(conn, "iris")
}

---

Method get_db_type()

Get the database type

Usage

DBISource$get_db_type()

Returns

A string identifying the database type

---

Method get_schema()

Get schema information for the database table

Usage

DBISource$get_schema(categorical_threshold = 20)

Arguments

categorical_threshold

Maximum number of unique values for a text column to be considered categorical (default: 20)

Returns

A string describing the schema

---

Method execute_query()

Execute a SQL query

Usage

DBISource$execute_query(query)

Arguments

query

SQL query string. If NULL or empty, returns all data

Returns

A data frame with query results

---

Method test_query()

Test a SQL query by fetching only one row

Usage

DBISource$test_query(query)

Arguments

query

SQL query string

Returns

A data frame with one row of results

---

Method get_data()

Get all data from the table

Usage

DBISource$get_data()

Returns

A data frame containing all data

---

Method cleanup()

Disconnect from the database

Usage

DBISource$cleanup()

Returns

NULL (invisibly)

---

Method clone()

The objects of this class are cloneable with this method.

Usage

DBISource$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

if (FALSE) { # \dontrun{
# Connect to a database
conn <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
DBI::dbWriteTable(conn, "mtcars", mtcars)

# Create a DBI source
db_source <- DBISource$new(conn, "mtcars")

# Get database type
db_source$get_db_type()  # Returns "SQLite"

# Execute a query
result <- db_source$execute_query("SELECT * FROM mtcars WHERE mpg > 25")

# Note: cleanup() will disconnect the connection
# If you want to keep the connection open, don't call cleanup()
} # }

## ------------------------------------------------
## Method `DBISource$new`
## ------------------------------------------------

if (FALSE) { # \dontrun{
conn <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
DBI::dbWriteTable(conn, "iris", iris)
source <- DBISource$new(conn, "iris")
} # }