Document which features are required, and add vtab usage examples (#669)

src/backup.rs

@@ -1,4 +1,4 @@
-//! Online SQLite backup API.
+//! `feature = "backup"` Online SQLite backup API.
 //!
 //! To create a `Backup`, you must have two distinct `Connection`s - one
 //! for the source (which can be used while the backup is running) and one for
@@ -43,7 +43,9 @@ use crate::error::{error_from_handle, error_from_sqlite_code};
 use crate::{Connection, DatabaseName, Result};
 
 impl Connection {
-    /// Back up the `name` database to the given destination path.
+    /// `feature = "backup"` Back up the `name` database to the given
+    /// destination path.
+    ///
     /// If `progress` is not `None`, it will be called periodically
     /// until the backup completes.
     ///
@@ -81,9 +83,9 @@ impl Connection {
         }
     }
 
-    /// Restore the given source path into the `name` database.
+    /// `feature = "backup"` Restore the given source path into the
-    /// If `progress` is not `None`, it will be called periodically
+    /// `name` database. If `progress` is not `None`, it will be
-    /// until the restore completes.
+    /// called periodically until the restore completes.
     ///
     /// For more fine-grained control over the restore process (e.g.,
     /// to sleep periodically during the restore or to restore from an
@@ -128,7 +130,7 @@ impl Connection {
     }
 }
 
-/// Possible successful results of calling `Backup::step`.
+/// `feature = "backup"` Possible successful results of calling `Backup::step`.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum StepResult {
     /// The backup is complete.
@@ -147,11 +149,11 @@ pub enum StepResult {
     Locked,
 }
 
-/// Struct specifying the progress of a backup. The percentage completion can
+/// `feature = "backup"` Struct specifying the progress of a backup. The
-/// be calculated as `(pagecount - remaining) / pagecount`. The progress of a
+/// percentage completion can be calculated as `(pagecount - remaining) /
-/// backup is as of the last call to `step` - if the source database is
+/// pagecount`. The progress of a backup is as of the last call to `step` - if
-/// modified after a call to `step`, the progress value will become outdated
+/// the source database is modified after a call to `step`, the progress value
-/// and potentially incorrect.
+/// will become outdated and potentially incorrect.
 #[derive(Copy, Clone, Debug)]
 pub struct Progress {
     /// Number of pages in the source database that still need to be backed up.
@@ -160,7 +162,7 @@ pub struct Progress {
     pub pagecount: c_int,
 }
 
-/// A handle to an online backup.
+/// `feature = "backup"` A handle to an online backup.
 pub struct Backup<'a, 'b> {
     phantom_from: PhantomData<&'a ()>,
     phantom_to: PhantomData<&'b ()>,

src/blob.rs

@@ -1,4 +1,4 @@
-//! Incremental BLOB I/O.
+//! `feature = "blob"` Incremental BLOB I/O.
 //!
 //! Note that SQLite does not provide API-level access to change the size of a
 //! BLOB; that must be performed through SQL statements.
@@ -60,7 +60,7 @@ use super::ffi;
 use super::types::{ToSql, ToSqlOutput};
 use crate::{Connection, DatabaseName, Result};
 
-/// Handle to an open BLOB.
+/// `feature = "blob"` Handle to an open BLOB.
 pub struct Blob<'conn> {
     conn: &'conn Connection,
     blob: *mut ffi::sqlite3_blob,
@@ -68,8 +68,8 @@ pub struct Blob<'conn> {
 }
 
 impl Connection {
-    /// Open a handle to the BLOB located in `row_id`, `column`, `table` in
+    /// `feature = "blob"` Open a handle to the BLOB located in `row_id`, `column`,
-    /// database `db`.
+    /// `table` in database `db`.
     ///
     /// # Failure
     ///
@@ -238,7 +238,7 @@ impl Drop for Blob<'_> {
     }
 }
 
-/// BLOB of length N that is filled with zeroes.
+/// `feature = "blob"` BLOB of length N that is filled with zeroes.
 ///
 /// Zeroblobs are intended to serve as placeholders for BLOBs whose content is
 /// later written using incremental BLOB I/O routines.

src/collation.rs

@@ -1,4 +1,4 @@
-//! Add, remove, or modify a collation
+//! `feature = "collation"` Add, remove, or modify a collation
 use std::cmp::Ordering;
 use std::os::raw::{c_char, c_int, c_void};
 use std::panic::{catch_unwind, UnwindSafe};
@@ -14,7 +14,7 @@ unsafe extern "C" fn free_boxed_value<T>(p: *mut c_void) {
 }
 
 impl Connection {
-    /// Add or modify a collation.
+    /// `feature = "collation"` Add or modify a collation.
     pub fn create_collation<C>(&self, collation_name: &str, x_compare: C) -> Result<()>
     where
         C: Fn(&str, &str) -> Ordering + Send + UnwindSafe + 'static,
@@ -24,7 +24,7 @@ impl Connection {
             .create_collation(collation_name, x_compare)
     }
 
-    /// Collation needed callback
+    /// `feature = "collation"` Collation needed callback
     pub fn collation_needed(
         &self,
         x_coll_needed: fn(&Connection, &str) -> Result<()>,
@@ -32,7 +32,7 @@ impl Connection {
         self.db.borrow_mut().collation_needed(x_coll_needed)
     }
 
-    /// Remove collation.
+    /// `feature = "collation"` Remove collation.
     pub fn remove_collation(&self, collation_name: &str) -> Result<()> {
         self.db.borrow_mut().remove_collation(collation_name)
     }

src/functions.rs

@@ -1,4 +1,4 @@
-//! Create or redefine SQL functions.
+//! `feature = "functions"` Create or redefine SQL functions.
 //!
 //! # Example
 //!
@@ -115,7 +115,8 @@ unsafe extern "C" fn free_boxed_value<T>(p: *mut c_void) {
     drop(Box::from_raw(p as *mut T));
 }
 
-/// Context is a wrapper for the SQLite function evaluation context.
+/// `feature = "functions"` Context is a wrapper for the SQLite function
+/// evaluation context.
 pub struct Context<'a> {
     ctx: *mut sqlite3_context,
     args: &'a [*mut sqlite3_value],
@@ -205,7 +206,8 @@ impl Context<'_> {
     }
 }
 
-/// Aggregate is the callback interface for user-defined aggregate function.
+/// `feature = "functions"` Aggregate is the callback interface for user-defined
+/// aggregate function.
 ///
 /// `A` is the type of the aggregation context and `T` is the type of the final
 /// result. Implementations should be stateless.
@@ -231,8 +233,8 @@ where
     fn finalize(&self, _: Option<A>) -> Result<T>;
 }
 
-/// WindowAggregate is the callback interface for user-defined aggregate window
+/// `feature = "window"` WindowAggregate is the callback interface for
-/// function.
+/// user-defined aggregate window function.
 #[cfg(feature = "window")]
 pub trait WindowAggregate<A, T>: Aggregate<A, T>
 where
@@ -270,7 +272,8 @@ impl Default for FunctionFlags {
 }
 
 impl Connection {
-    /// Attach a user-defined scalar function to this database connection.
+    /// `feature = "functions"` Attach a user-defined scalar function to
+    /// this database connection.
     ///
     /// `fn_name` is the name the function will be accessible from SQL.
     /// `n_arg` is the number of arguments to the function. Use `-1` for a
@@ -321,7 +324,8 @@ impl Connection {
             .create_scalar_function(fn_name, n_arg, flags, x_func)
     }
 
-    /// Attach a user-defined aggregate function to this database connection.
+    /// `feature = "functions"` Attach a user-defined aggregate function to this
+    /// database connection.
     ///
     /// # Failure
     ///
@@ -343,6 +347,11 @@ impl Connection {
             .create_aggregate_function(fn_name, n_arg, flags, aggr)
     }
 
+    /// `feature = "window"` Attach a user-defined aggregate window function to
+    /// this database connection.
+    ///
+    /// See https://sqlite.org/windowfunctions.html#udfwinfunc for more
+    /// information.
     #[cfg(feature = "window")]
     pub fn create_window_function<A, W, T>(
         &self,
@@ -361,7 +370,8 @@ impl Connection {
             .create_window_function(fn_name, n_arg, flags, aggr)
     }
 
-    /// Removes a user-defined function from this database connection.
+    /// `feature = "functions"` Removes a user-defined function from this
+    /// database connection.
     ///
     /// `fn_name` and `n_arg` should match the name and number of arguments
     /// given to `create_scalar_function` or `create_aggregate_function`.

src/hooks.rs

@@ -1,4 +1,4 @@
-//! Commit, Data Change and Rollback Notification Callbacks
+//! `feature = "hooks"` Commit, Data Change and Rollback Notification Callbacks
 #![allow(non_camel_case_types)]
 
 use std::os::raw::{c_char, c_int, c_void};
@@ -9,7 +9,7 @@ use crate::ffi;
 
 use crate::{Connection, InnerConnection};
 
-/// Action Codes
+/// `feature = "hooks"` Action Codes
 #[derive(Clone, Copy, Debug, PartialEq)]
 #[repr(i32)]
 pub enum Action {
@@ -31,8 +31,8 @@ impl From<i32> for Action {
 }
 
 impl Connection {
-    /// Register a callback function to be invoked whenever a transaction is
+    /// `feature = "hooks"` Register a callback function to be invoked whenever
-    /// committed.
+    /// a transaction is committed.
     ///
     /// The callback returns `true` to rollback.
     pub fn commit_hook<F>(&self, hook: Option<F>)
@@ -42,8 +42,8 @@ impl Connection {
         self.db.borrow_mut().commit_hook(hook);
     }
 
-    /// Register a callback function to be invoked whenever a transaction is
+    /// `feature = "hooks"` Register a callback function to be invoked whenever
-    /// committed.
+    /// a transaction is committed.
     ///
     /// The callback returns `true` to rollback.
     pub fn rollback_hook<F>(&self, hook: Option<F>)
@@ -53,8 +53,8 @@ impl Connection {
         self.db.borrow_mut().rollback_hook(hook);
     }
 
-    /// Register a callback function to be invoked whenever a row is updated,
+    /// `feature = "hooks"` Register a callback function to be invoked whenever
-    /// inserted or deleted in a rowid table.
+    /// a row is updated, inserted or deleted in a rowid table.
     ///
     /// The callback parameters are:
     ///

src/lib.rs

@@ -653,8 +653,8 @@ impl Connection {
         r.map_err(move |err| (self, err))
     }
 
-    /// Enable loading of SQLite extensions. Strongly consider using
+    /// `feature = "load_extension"` Enable loading of SQLite extensions.
-    /// `LoadExtensionGuard` instead of this function.
+    /// Strongly consider using `LoadExtensionGuard` instead of this function.
     ///
     /// ## Example
     ///
@@ -676,7 +676,7 @@ impl Connection {
         self.db.borrow_mut().enable_load_extension(1)
     }
 
-    /// Disable loading of SQLite extensions.
+    /// `feature = "load_extension"` Disable loading of SQLite extensions.
     ///
     /// See `load_extension_enable` for an example.
     ///
@@ -688,9 +688,9 @@ impl Connection {
         self.db.borrow_mut().enable_load_extension(0)
     }
 
-    /// Load the SQLite extension at `dylib_path`. `dylib_path` is passed
+    /// `feature = "load_extension"` Load the SQLite extension at `dylib_path`.
-    /// through to `sqlite3_load_extension`, which may attempt OS-specific
+    /// `dylib_path` is passed through to `sqlite3_load_extension`, which may
-    /// modifications if the file cannot be loaded directly.
+    /// attempt OS-specific modifications if the file cannot be loaded directly.
     ///
     /// If `entry_point` is `None`, SQLite will attempt to find the entry
     /// point. If it is not `None`, the entry point will be passed through

src/limits.rs

@@ -1,4 +1,4 @@
-//! Run-Time Limits
+//! `feature = "limits"` Run-Time Limits
 
 use std::os::raw::c_int;
 
@@ -8,13 +8,14 @@ pub use crate::ffi::Limit;
 use crate::Connection;
 
 impl Connection {
-    /// Returns the current value of a limit.
+    /// `feature = "limits"` Returns the current value of a limit.
     pub fn limit(&self, limit: Limit) -> i32 {
         let c = self.db.borrow();
         unsafe { ffi::sqlite3_limit(c.db(), limit as c_int, -1) }
     }
 
-    /// Changes the limit to `new_val`, returning the prior value of the limit.
+    /// `feature = "limits"` Changes the limit to `new_val`, returning the prior
+    /// value of the limit.
     pub fn set_limit(&self, limit: Limit, new_val: i32) -> i32 {
         let c = self.db.borrow_mut();
         unsafe { ffi::sqlite3_limit(c.db(), limit as c_int, new_val) }

src/load_extension_guard.rs

@@ -1,6 +1,7 @@
 use crate::{Connection, Result};
 
-/// RAII guard temporarily enabling SQLite extensions to be loaded.
+/// `feature = "load_extension"` RAII guard temporarily enabling SQLite
+/// extensions to be loaded.
 ///
 /// ## Example
 ///

src/session.rs

@@ -1,4 +1,4 @@
-//! [Session Extension](https://sqlite.org/sessionintro.html)
+//! `feature = "session"` [Session Extension](https://sqlite.org/sessionintro.html)
 #![allow(non_camel_case_types)]
 
 use std::ffi::CStr;
@@ -20,7 +20,7 @@ use crate::{errmsg_to_string, str_to_cstring, Connection, DatabaseName, Result};
 
 // https://sqlite.org/session.html
 
-/// An instance of this object is a session that can be used to record changes
+/// `feature = "session"` An instance of this object is a session that can be used to record changes
 /// to a database.
 pub struct Session<'conn> {
     phantom: PhantomData<&'conn ()>,
@@ -211,7 +211,7 @@ impl Drop for Session<'_> {
     }
 }
 
-/// Invert a changeset
+/// `feature = "session"` Invert a changeset
 pub fn invert_strm(input: &mut dyn Read, output: &mut dyn Write) -> Result<()> {
     let input_ref = &input;
     let output_ref = &output;
@@ -226,7 +226,7 @@ pub fn invert_strm(input: &mut dyn Read, output: &mut dyn Write) -> Result<()> {
     Ok(())
 }
 
-/// Combine two changesets
+/// `feature = "session"` Combine two changesets
 pub fn concat_strm(
     input_a: &mut dyn Read,
     input_b: &mut dyn Read,
@@ -248,7 +248,7 @@ pub fn concat_strm(
     Ok(())
 }
 
-/// Changeset or Patchset
+/// `feature = "session"` Changeset or Patchset
 pub struct Changeset {
     cs: *mut c_void,
     n: c_int,
@@ -296,7 +296,8 @@ impl Drop for Changeset {
     }
 }
 
-/// Cursor for iterating over the elements of a changeset or patchset.
+/// `feature = "session"` Cursor for iterating over the elements of a changeset
+/// or patchset.
 pub struct ChangesetIter<'changeset> {
     phantom: PhantomData<&'changeset ()>,
     it: *mut ffi::sqlite3_changeset_iter,
@@ -347,6 +348,7 @@ impl FallibleStreamingIterator for ChangesetIter<'_> {
     }
 }
 
+/// `feature = "session"`
 pub struct Operation<'item> {
     table_name: &'item str,
     number_of_columns: i32,
@@ -380,7 +382,7 @@ impl Drop for ChangesetIter<'_> {
     }
 }
 
-/// An item passed to a conflict-handler by `Connection::apply`,
+/// `feature = "session"` An item passed to a conflict-handler by `Connection::apply`,
 /// or an item generated by `ChangesetIter::next`.
 // TODO enum ? Delete, Insert, Update, ...
 pub struct ChangesetItem {
@@ -493,7 +495,7 @@ impl ChangesetItem {
     }
 }
 
-/// Used to combine two or more changesets or
+/// `feature = "session"` Used to combine two or more changesets or
 /// patchsets
 pub struct Changegroup {
     cg: *mut ffi::sqlite3_changegroup,
@@ -558,7 +560,7 @@ impl Drop for Changegroup {
 }
 
 impl Connection {
-    /// Apply a changeset to a database
+    /// `feature = "session"` Apply a changeset to a database
     pub fn apply<F, C>(&self, cs: &Changeset, filter: Option<F>, conflict: C) -> Result<()>
     where
         F: Fn(&str) -> bool + Send + RefUnwindSafe + 'static,
@@ -592,7 +594,7 @@ impl Connection {
         Ok(())
     }
 
-    /// Apply a changeset to a database
+    /// `feature = "session"` Apply a changeset to a database
     pub fn apply_strm<F, C>(
         &self,
         input: &mut dyn Read,
@@ -633,7 +635,7 @@ impl Connection {
     }
 }
 
-/// Constants passed to the conflict handler
+/// `feature = "session"` Constants passed to the conflict handler
 #[repr(i32)]
 #[derive(Debug, PartialEq)]
 pub enum ConflictType {
@@ -657,7 +659,7 @@ impl From<i32> for ConflictType {
     }
 }
 
-/// Constants returned by the conflict handler
+/// `feature = "session"` Constants returned by the conflict handler
 #[repr(i32)]
 #[derive(Debug, PartialEq)]
 pub enum ConflictAction {

src/trace.rs

@@ -1,4 +1,4 @@
-//! Tracing and profiling functions. Error and warning log.
+//! `feature = "trace"` Tracing and profiling functions. Error and warning log.
 
 use std::ffi::{CStr, CString};
 use std::mem;
@@ -11,7 +11,7 @@ use super::ffi;
 use crate::error::error_from_sqlite_code;
 use crate::{Connection, Result};
 
-/// Set up the process-wide SQLite error logging callback.
+/// `feature = "trace"` Set up the process-wide SQLite error logging callback.
 ///
 /// # Safety
 ///
@@ -56,7 +56,8 @@ pub unsafe fn config_log(callback: Option<fn(c_int, &str)>) -> Result<()> {
     }
 }
 
-/// Write a message into the error log established by `config_log`.
+/// `feature = "trace"` Write a message into the error log established by
+/// `config_log`.
 pub fn log(err_code: c_int, msg: &str) {
     let msg = CString::new(msg).expect("SQLite log messages cannot contain embedded zeroes");
     unsafe {
@@ -65,8 +66,8 @@ pub fn log(err_code: c_int, msg: &str) {
 }
 
 impl Connection {
-    /// Register or clear a callback function that can be used for tracing the
+    /// `feature = "trace"` Register or clear a callback function that can be
-    /// execution of SQL statements.
+    /// used for tracing the execution of SQL statements.
     ///
     /// Prepared statement placeholders are replaced/logged with their assigned
     /// values. There can only be a single tracer defined for each database
@@ -90,8 +91,8 @@ impl Connection {
         }
     }
 
-    /// Register or clear a callback function that can be used for profiling
+    /// `feature = "trace"` Register or clear a callback function that can be
-    /// the execution of SQL statements.
+    /// used for profiling the execution of SQL statements.
     ///
     /// There can only be a single profiler defined for each database
     /// connection. Setting a new profiler clears the old one.

src/types/from_sql.rs

@@ -13,13 +13,14 @@ pub enum FromSqlError {
     /// requested type.
     OutOfRange(i64),
 
-    /// Error returned when reading an `i128` from a blob with a size
+    /// `feature = "i128_blob"` Error returned when reading an `i128` from a
-    /// other than 16. Only available when the `i128_blob` feature is enabled.
+    /// blob with a size other than 16. Only available when the `i128_blob`
+    /// feature is enabled.
     #[cfg(feature = "i128_blob")]
     InvalidI128Size(usize),
 
-    /// Error returned when reading a `uuid` from a blob with a size
+    /// `feature = "uuid"` Error returned when reading a `uuid` from a blob with
-    /// other than 16. Only available when the `uuid` feature is enabled.
+    /// a size other than 16. Only available when the `uuid` feature is enabled.
     #[cfg(feature = "uuid")]
     InvalidUuidSize(usize),
 

src/types/to_sql.rs

@@ -14,10 +14,12 @@ pub enum ToSqlOutput<'a> {
     /// An owned SQLite-representable value.
     Owned(Value),
 
-    /// A BLOB of the given length that is filled with zeroes.
+    /// `feature = "blob"` A BLOB of the given length that is filled with
+    /// zeroes.
     #[cfg(feature = "blob")]
     ZeroBlob(i32),
 
+    /// `feature = "array"`
     #[cfg(feature = "array")]
     Array(Array),
 }

src/vtab/array.rs

@@ -1,6 +1,30 @@
-//! Array Virtual Table.
+//! `feature = "array"` Array Virtual Table: https://www.sqlite.org/carray.html
+//!
+//! Note: `rarray`, not `carray` is the name of the table valued function we
+//! define.
 //!
 //! Port of [carray](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/carray.c) C extension.
+//!
+//! # Example
+//!
+//! ```rust,no_run
+//! # use rusqlite::{types::Value, Connection, Result, params};
+//! # use std::rc::Rc;
+//! fn example(db: &Connection) -> Result<()> {
+//!     // Note: This should be done once (usually when opening the DB).
+//!     rusqlite::vtab::array::load_module(&db)?;
+//!     let v = [1i64, 2, 3, 4];
+//!     // Note: A `Rc<Vec<Value>>` must be used as the parameter.
+//!     let values = Rc::new(v.iter().copied().map(Value::from).collect::<Vec<Value>>());
+//!     let mut stmt = db.prepare("SELECT value from rarray(?);")?;
+//!     let rows = stmt.query_map(params![values], |row| row.get::<_, i64>(0))?;
+//!     for value in rows {
+//!         println!("{}", value?);
+//!     }
+//!     Ok(())
+//! }
+//! ```
+
 use std::default::Default;
 use std::os::raw::{c_char, c_int, c_void};
 use std::rc::Rc;
@@ -29,7 +53,7 @@ impl ToSql for Array {
     }
 }
 
-/// Register the "rarray" module.
+/// `feature = "array"` Register the "rarray" module.
 pub fn load_module(conn: &Connection) -> Result<()> {
     let aux: Option<()> = None;
     conn.create_module("rarray", &ARRAY_MODULE, aux)

src/vtab/csvtab.rs

@@ -1,6 +1,25 @@
-//! CSV Virtual Table.
+//! `feature = "csvtab"` CSV Virtual Table: https://www.sqlite.org/csv.html
 //!
 //! Port of [csv](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/csv.c) C extension.
+//!
+//! # Example
+//!
+//! ```rust,no_run
+//! # use rusqlite::{Connection, Result};
+//! fn example() -> Result<()> {
+//!     // Note: This should be done once (usually when opening the DB).
+//!     let db = Connection::open_in_memory()?;
+//!     rusqlite::vtab::csvtab::load_module(&db)?;
+//!     // Assum3e my_csv.csv
+//!     let schema = "
+//!         CREATE VIRTUAL TABLE my_csv_data
+//!         USING csv(filename = 'my_csv.csv')
+//!     ";
+//!     db.execute_batch(schema)?;
+//!     // Now the `my_csv_data` (virtual) table can be queried as normal...
+//!     Ok(())
+//! }
+//! ```
 use std::fs::File;
 use std::os::raw::c_int;
 use std::path::Path;
@@ -15,7 +34,7 @@ use crate::vtab::{
 };
 use crate::{Connection, Error, Result};
 
-/// Register the "csv" module.
+/// `feature = "csvtab"` Register the "csv" module.
 /// ```sql
 /// CREATE VIRTUAL TABLE vtab USING csv(
 ///   filename=FILENAME -- Name of file containing CSV content

src/vtab/mod.rs

@@ -1,4 +1,4 @@
-//! Create virtual tables.
+//! `feature = "vtab"` Create virtual tables.
 //!
 //! Follow these steps to create your own virtual table:
 //! 1. Write implemenation of `VTab` and `VTabCursor` traits.
@@ -57,7 +57,7 @@ use crate::{str_to_cstring, Connection, Error, InnerConnection, Result};
 // ffi::sqlite3_vtab => VTab
 // ffi::sqlite3_vtab_cursor => VTabCursor
 
-/// Virtual table module
+/// `feature = "vtab"` Virtual table module
 ///
 /// (See [SQLite doc](https://sqlite.org/c3ref/module.html))
 #[repr(C)]
@@ -77,7 +77,7 @@ fn zeroed_module() -> ffi::sqlite3_module {
     unsafe { std::mem::MaybeUninit::zeroed().assume_init() }
 }
 
-/// Create a read-only virtual table implementation.
+/// `feature = "vtab"` Create a read-only virtual table implementation.
 ///
 /// Step 2 of [Creating New Virtual Table Implementations](https://sqlite.org/vtab.html#creating_new_virtual_table_implementations).
 pub fn read_only_module<T: CreateVTab>(version: c_int) -> Module<T> {
@@ -115,7 +115,7 @@ pub fn read_only_module<T: CreateVTab>(version: c_int) -> Module<T> {
     }
 }
 
-/// Create an eponymous only virtual table implementation.
+/// `feature = "vtab"` Create an eponymous only virtual table implementation.
 ///
 /// Step 2 of [Creating New Virtual Table Implementations](https://sqlite.org/vtab.html#creating_new_virtual_table_implementations).
 pub fn eponymous_only_module<T: VTab>(version: c_int) -> Module<T> {
@@ -154,6 +154,7 @@ pub fn eponymous_only_module<T: VTab>(version: c_int) -> Module<T> {
     }
 }
 
+/// `feature = "vtab"`
 pub struct VTabConnection(*mut ffi::sqlite3);
 
 impl VTabConnection {
@@ -179,7 +180,7 @@ impl VTabConnection {
     }
 }
 
-/// Virtual table instance trait.
+/// `feature = "vtab"` Virtual table instance trait.
 ///
 /// Implementations must be like:
 /// ```rust,ignore
@@ -214,7 +215,7 @@ pub trait VTab: Sized {
     fn open(&self) -> Result<Self::Cursor>;
 }
 
-/// Non-eponymous virtual table instance trait.
+/// `feature = "vtab"` Non-eponymous virtual table instance trait.
 ///
 /// (See [SQLite doc](https://sqlite.org/c3ref/vtab.html))
 pub trait CreateVTab: VTab {
@@ -243,7 +244,7 @@ pub trait CreateVTab: VTab {
     }
 }
 
-///Index constraint operator.
+/// `feature = "vtab"` Index constraint operator.
 #[derive(Debug, PartialEq)]
 #[allow(non_snake_case, non_camel_case_types)]
 pub enum IndexConstraintOp {
@@ -286,8 +287,8 @@ impl From<u8> for IndexConstraintOp {
     }
 }
 
-/// Pass information into and receive the reply from the `VTab.best_index`
+/// `feature = "vtab"` Pass information into and receive the reply from the
-/// method.
+/// `VTab.best_index` method.
 ///
 /// (See [SQLite doc](http://sqlite.org/c3ref/index_info.html))
 pub struct IndexInfo(*mut ffi::sqlite3_index_info);
@@ -358,6 +359,7 @@ impl IndexInfo {
     // TODO sqlite3_vtab_collation (http://sqlite.org/c3ref/vtab_collation.html)
 }
 
+/// `feature = "vtab"`
 pub struct IndexConstraintIter<'a> {
     iter: slice::Iter<'a, ffi::sqlite3_index_constraint>,
 }
@@ -374,7 +376,7 @@ impl<'a> Iterator for IndexConstraintIter<'a> {
     }
 }
 
-/// WHERE clause constraint
+/// `feature = "vtab"` WHERE clause constraint.
 pub struct IndexConstraint<'a>(&'a ffi::sqlite3_index_constraint);
 
 impl IndexConstraint<'_> {
@@ -394,7 +396,7 @@ impl IndexConstraint<'_> {
     }
 }
 
-/// Information about what parameters to pass to `VTabCursor.filter`.
+/// `feature = "vtab"` Information about what parameters to pass to `VTabCursor.filter`.
 pub struct IndexConstraintUsage<'a>(&'a mut ffi::sqlite3_index_constraint_usage);
 
 impl IndexConstraintUsage<'_> {
@@ -409,6 +411,7 @@ impl IndexConstraintUsage<'_> {
     }
 }
 
+/// `feature = "vtab"`
 pub struct OrderByIter<'a> {
     iter: slice::Iter<'a, ffi::sqlite3_index_info_sqlite3_index_orderby>,
 }
@@ -425,7 +428,7 @@ impl<'a> Iterator for OrderByIter<'a> {
     }
 }
 
-/// A column of the ORDER BY clause.
+/// `feature = "vtab"` A column of the ORDER BY clause.
 pub struct OrderBy<'a>(&'a ffi::sqlite3_index_info_sqlite3_index_orderby);
 
 impl OrderBy<'_> {
@@ -440,7 +443,7 @@ impl OrderBy<'_> {
     }
 }
 
-/// Virtual table cursor trait.
+/// `feature = "vtab"` Virtual table cursor trait.
 ///
 /// Implementations must be like:
 /// ```rust,ignore
@@ -474,7 +477,7 @@ pub trait VTabCursor: Sized {
     fn rowid(&self) -> Result<i64>;
 }
 
-/// Context is used by `VTabCursor.column` to specify the cell value.
+/// `feature = "vtab"` Context is used by `VTabCursor.column` to specify the cell value.
 pub struct Context(*mut ffi::sqlite3_context);
 
 impl Context {
@@ -487,8 +490,8 @@ impl Context {
     // TODO sqlite3_vtab_nochange (http://sqlite.org/c3ref/vtab_nochange.html)
 }
 
-/// Wrapper to `VTabCursor.filter` arguments, the values requested by
+/// `feature = "vtab"` Wrapper to `VTabCursor.filter` arguments, the values
-/// `VTab.best_index`.
+/// requested by `VTab.best_index`.
 pub struct Values<'a> {
     args: &'a [*mut ffi::sqlite3_value],
 }
@@ -576,7 +579,7 @@ impl<'a> Iterator for ValueIter<'a> {
 }
 
 impl Connection {
-    /// Register a virtual table implementation.
+    /// `feature = "vtab"` Register a virtual table implementation.
     ///
     /// Step 3 of [Creating New Virtual Table Implementations](https://sqlite.org/vtab.html#creating_new_virtual_table_implementations).
     pub fn create_module<T: VTab>(
@@ -624,7 +627,8 @@ impl InnerConnection {
     }
 }
 
-/// Escape double-quote (`"`) character occurences by doubling them (`""`).
+/// `feature = "vtab"` Escape double-quote (`"`) character occurences by
+/// doubling them (`""`).
 pub fn escape_double_quote(identifier: &str) -> Cow<'_, str> {
     if identifier.contains('"') {
         // escape quote by doubling them
@@ -633,7 +637,7 @@ pub fn escape_double_quote(identifier: &str) -> Cow<'_, str> {
         Borrowed(identifier)
     }
 }
-/// Dequote string
+/// `feature = "vtab"` Dequote string
 pub fn dequote(s: &str) -> &str {
     if s.len() < 2 {
         return s;
@@ -646,7 +650,7 @@ pub fn dequote(s: &str) -> &str {
         _ => s,
     }
 }
-/// The boolean can be one of:
+/// `feature = "vtab"` The boolean can be one of:
 /// ```text
 /// 1 yes true on
 /// 0 no false off

src/vtab/series.rs

@@ -1,4 +1,4 @@
-//! generate series virtual table.
+//! `feature = "series"` Generate series virtual table: https://www.sqlite.org/series.html
 //!
 //! Port of C [generate series "function"](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/series.c).
 use std::default::Default;
@@ -12,7 +12,7 @@ use crate::vtab::{
 };
 use crate::{Connection, Result};
 
-/// Register the "generate_series" module.
+/// `feature = "series"` Register the "generate_series" module.
 pub fn load_module(conn: &Connection) -> Result<()> {
     let aux: Option<()> = None;
     conn.create_module("generate_series", &SERIES_MODULE, aux)