feat(r/DataFrameSource): Use duckdb or SQLite (first available) (#178)

* refactor: DataFrameSource extends DBISource

* feat(DataFrameSource): Choose between duckdb and sqlite engines

* chore: Make duckdb an optional dependency

* feat: Use duckdb or sqlite based on first available

* chore(pkg-r): Avoid CRAN note about whisker

* ci(pkg-r): Don't check-depends-only

* chore: Add NEWS item

Author: gadenbuie

.github/workflows/R-CMD-check.yml

@@ -31,3 +31,4 @@ jobs:
     uses: rstudio/shiny-workflows/.github/workflows/R-CMD-check.yaml@v1
     with:
       working-directory: ./pkg-r
+      check-depends-only: false

pkg-r/DESCRIPTION

@@ -24,7 +24,6 @@ Imports:
     bslib,
     cli,
     DBI,
-    duckdb,
     ellmer (>= 0.3.0),
     htmltools,
     lifecycle,
@@ -39,14 +38,15 @@ Imports:
 Suggests:
     bsicons,
     DT,
+    duckdb,
     knitr,
     palmerpenguins,
     rmarkdown,
     RSQLite,
     shinytest2,
     testthat (>= 3.0.0),
     withr
-VignetteBuilder: 
+VignetteBuilder:
     knitr
 Remotes:
     posit-dev/shinychat/pkg-r

pkg-r/NEWS.md

@@ -1,5 +1,7 @@
 # querychat (development version)
 
+* `querychat()` and `QueryChat$new()` now use either `{duckdb}` or `{SQLite}` for the in-memory database backend for data frames, depending on which package is installed. If both are installed, `{duckdb}` will be preferred. You can explicitly choose the `engine` in `DataFrameSource$new()` or set `querychat.DataFrameSource.engine` option to choose a global default. (#178)
+
 * `QueryChat$sidebar()`, `QueryChat$ui()`, and `QueryChat$server()` now support an optional `id` parameter to enable use within Shiny modules. When used in a module UI function, pass `id = ns("your_id")` where `ns` is the namespacing function from `shiny::NS()`. In the corresponding module server function, pass the unwrapped ID to `QueryChat$server(id = "your_id")`. This enables multiple independent QueryChat instances from the same QueryChat object. (#172)
 
 * `QueryChat$client()` can now create standalone querychat-enabled chat clients with configurable tools and callbacks, enabling use outside of Shiny applications. (#168)

pkg-r/R/DataSource.R

@@ -89,31 +89,43 @@ DataSource <- R6::R6Class(
 #' Data Frame Source
 #'
 #' @description
-#' A DataSource implementation that wraps a data frame using DuckDB for SQL
-#' query execution.
+#' A DataSource implementation that wraps a data frame using DuckDB or SQLite
+#' for SQL query execution.
 #'
 #' @details
-#' This class creates an in-memory DuckDB connection and registers the provided
-#' data frame as a table. All SQL queries are executed against this DuckDB table.
+#' This class creates an in-memory database connection and registers the
+#' provided data frame as a table. All SQL queries are executed against this
+#' database table. See [DBISource] for the full description of available
+#' methods.
+#'
+#' By default, DataFrameSource uses the first available engine from duckdb
+#' (checked first) or RSQLite. You can explicitly set the `engine` parameter to
+#' choose between "duckdb" or "sqlite", or set the global option
+#' `querychat.DataFrameSource.engine` to choose the default engine for all
+#' DataFrameSource instances. At least one of these packages must be installed.
 #'
 #' @export
 #' @examples
 #' \dontrun{
-#' # Create a data frame source
+#' # Create a data frame source (uses first available: duckdb or sqlite)
 #' df_source <- DataFrameSource$new(mtcars, "mtcars")
 #'
 #' # Get database type
-#' df_source$get_db_type()  # Returns "DuckDB"
+#' df_source$get_db_type()  # Returns "DuckDB" or "SQLite"
 #'
 #' # Execute a query
 #' result <- df_source$execute_query("SELECT * FROM mtcars WHERE mpg > 25")
 #'
+#' # Explicitly choose an engine
+#' df_sqlite <- DataFrameSource$new(mtcars, "mtcars", engine = "sqlite")
+#'
 #' # Clean up when done
 #' df_source$cleanup()
+#' df_sqlite$cleanup()
 #' }
 DataFrameSource <- R6::R6Class(
   "DataFrameSource",
-  inherit = DataSource,
+  inherit = DBISource,
   private = list(
     conn = NULL
   ),
@@ -125,94 +137,44 @@ DataFrameSource <- R6::R6Class(
     #' @param table_name Name to use for the table in SQL queries. Must be a
     #'   valid table name (start with letter, contain only letters, numbers,
     #'   and underscores)
+    #' @param engine Database engine to use: "duckdb" or "sqlite". Set the
+    #'   global option `querychat.DataFrameSource.engine` to specify the default
+    #'   engine for all instances. If NULL (default), uses the first available
+    #'   engine from duckdb or RSQLite (in that order).
     #' @return A new DataFrameSource object
     #' @examples
     #' \dontrun{
     #' source <- DataFrameSource$new(iris, "iris")
     #' }
-    initialize = function(df, table_name) {
+    initialize = function(
+      df,
+      table_name,
+      engine = getOption("querychat.DataFrameSource.engine", NULL)
+    ) {
       check_data_frame(df)
       check_sql_table_name(table_name)
 
-      self$table_name <- table_name
-
-      # Create DuckDB connection and register the data frame
-      private$conn <- DBI::dbConnect(duckdb::duckdb(), dbdir = ":memory:")
-      duckdb::duckdb_register(
-        private$conn,
-        table_name,
-        df,
-        experimental = FALSE
-      )
-    },
+      engine <- engine %||% get_default_dataframe_engine()
+      engine <- tolower(engine)
+      arg_match(engine, c("duckdb", "sqlite"))
 
-    #' @description Get the database type
-    #' @return The string "DuckDB"
-    get_db_type = function() {
-      "DuckDB"
-    },
-
-    #' @description
-    #' Get schema information for the data frame
-    #'
-    #' @param categorical_threshold Maximum number of unique values for a text
-    #'   column to be considered categorical (default: 20)
-    #' @return A string describing the schema
-    get_schema = function(categorical_threshold = 20) {
-      check_number_whole(categorical_threshold, min = 1)
-      get_schema_impl(private$conn, self$table_name, categorical_threshold)
-    },
+      self$table_name <- table_name
 
-    #' @description
-    #' Execute a SQL query
-    #'
-    #' @param query SQL query string. If NULL or empty, returns all data
-    #' @return A data frame with query results
-    execute_query = function(query) {
-      check_string(query, allow_null = TRUE, allow_empty = TRUE)
-      if (is.null(query) || !nzchar(query)) {
-        query <- paste0(
-          "SELECT * FROM ",
-          DBI::dbQuoteIdentifier(private$conn, self$table_name)
+      # Create in-memory connection and register the data frame
+      if (engine == "duckdb") {
+        check_installed("duckdb")
+        private$conn <- DBI::dbConnect(duckdb::duckdb(), dbdir = ":memory:")
+        duckdb::duckdb_register(
+          private$conn,
+          table_name,
+          df,
+          experimental = FALSE
         )
+      } else if (engine == "sqlite") {
+        check_installed("RSQLite")
+        private$conn <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
+        DBI::dbWriteTable(private$conn, table_name, df)
       }
-      DBI::dbGetQuery(private$conn, query)
-    },
-
-    #' @description
-    #' Test a SQL query by fetching only one row
-    #'
-    #' @param query SQL query string
-    #' @return A data frame with one row of results
-    test_query = function(query) {
-      check_string(query, allow_null = TRUE, allow_empty = TRUE)
-      if (is.null(query) || !nzchar(query)) {
-        return(invisible(NULL))
-      }
-
-      rs <- DBI::dbSendQuery(private$conn, query)
-      df <- DBI::dbFetch(rs, n = 1)
-      DBI::dbClearResult(rs)
-      df
-    },
-
-    #' @description
-    #' Get all data from the table
-    #'
-    #' @return A data frame containing all data
-    get_data = function() {
-      self$execute_query(NULL)
-    },
-
-    #' @description
-    #' Close the DuckDB connection
-    #'
-    #' @return NULL (invisibly)
-    cleanup = function() {
-      if (!is.null(private$conn) && DBI::dbIsValid(private$conn)) {
-        DBI::dbDisconnect(private$conn)
-      }
-      invisible(NULL)
     }
   )
 )
@@ -390,6 +352,22 @@ is_data_source <- function(x) {
 }
 
 
+get_default_dataframe_engine <- function() {
+  if (is_installed("duckdb")) {
+    return("duckdb")
+  }
+  if (is_installed("RSQLite")) {
+    return("sqlite")
+  }
+  cli::cli_abort(c(
+    "No compatible database engine installed for DataFrameSource",
+    "i" = "Install either {.pkg duckdb} or {.pkg RSQLite}:",
+    " " = "{.run install.packages(\"duckdb\")}",
+    " " = "{.run install.packages(\"RSQLite\")}"
+  ))
+}
+
+
 get_schema_impl <- function(conn, table_name, categorical_threshold = 20) {
   # Get column information
   columns <- DBI::dbListFields(conn, table_name)

pkg-r/R/querychat-package.R

@@ -84,6 +84,6 @@ release_bullets <- function() {
 }
 
 suppress_rcmdcheck <- function() {
-  duckdb::duckdb
   S7::S7_class
+  whisker::whisker.render
 }