Merge 'Add the .indexes command' from Anton Harniakou

Adds ability to view database indices using the `.indexes ?TABLE?`
command.

Closes #1409

cli/app.rs

@@ -641,6 +641,11 @@ impl Limbo {
                         let _ = self.writeln(v);
                     });
                 }
+                Command::ListIndexes(args) => {
+                    if let Err(e) = self.display_indexes(args.tbl_name) {
+                        let _ = self.writeln(e.to_string());
+                    }
+                }
                 Command::Timer(timer_mode) => {
                     self.opts.timer = match timer_mode.mode {
                         TimerMode::On => true,
@@ -916,6 +921,55 @@ impl Limbo {
         Ok(())
     }
 
+    fn display_indexes(&mut self, maybe_table: Option<String>) -> anyhow::Result<()> {
+        let sql = match maybe_table {
+            Some(ref tbl_name) => format!(
+                "SELECT name FROM sqlite_schema WHERE type='index' AND tbl_name = '{}' ORDER BY 1",
+                tbl_name
+            ),
+            None => String::from("SELECT name FROM sqlite_schema WHERE type='index' ORDER BY 1"),
+        };
+
+        match self.conn.query(&sql) {
+            Ok(Some(ref mut rows)) => {
+                let mut indexes = String::new();
+                loop {
+                    match rows.step()? {
+                        StepResult::Row => {
+                            let row = rows.row().unwrap();
+                            if let Ok(OwnedValue::Text(idx)) = row.get::<&OwnedValue>(0) {
+                                indexes.push_str(idx.as_str());
+                                indexes.push(' ');
+                            }
+                        }
+                        StepResult::IO => {
+                            self.io.run_once()?;
+                        }
+                        StepResult::Interrupt => break,
+                        StepResult::Done => break,
+                        StepResult::Busy => {
+                            let _ = self.writeln("database is busy");
+                            break;
+                        }
+                    }
+                }
+                if !indexes.is_empty() {
+                    let _ = self.writeln(indexes.trim_end());
+                }
+            }
+            Err(err) => {
+                if err.to_string().contains("no such table: sqlite_schema") {
+                    return Err(anyhow::anyhow!("Unable to access database schema. The database may be using an older SQLite version or may not be properly initialized."));
+                } else {
+                    return Err(anyhow::anyhow!("Error querying schema: {}", err));
+                }
+            }
+            Ok(None) => {}
+        }
+
+        Ok(())
+    }
+
     fn display_tables(&mut self, pattern: Option<&str>) -> anyhow::Result<()> {
         let sql = match pattern {
             Some(pattern) => format!(

cli/commands/args.rs

@@ -3,6 +3,12 @@ use clap_complete::{ArgValueCompleter, CompletionCandidate, PathCompleter};
 
 use crate::{input::OutputMode, opcodes_dictionary::OPCODE_DESCRIPTIONS};
 
+#[derive(Debug, Clone, Args)]
+pub struct IndexesArgs {
+    /// Name of table
+    pub tbl_name: Option<String>,
+}
+
 #[derive(Debug, Clone, Args)]
 pub struct ExitArgs {
     /// Exit code

cli/commands/mod.rs

@@ -2,8 +2,8 @@ pub mod args;
 pub mod import;
 
 use args::{
-    CwdArgs, EchoArgs, ExitArgs, LoadExtensionArgs, NullValueArgs, OpcodesArgs, OpenArgs,
-    OutputModeArgs, SchemaArgs, SetOutputArgs, TablesArgs, TimerArgs,
+    CwdArgs, EchoArgs, ExitArgs, IndexesArgs, LoadExtensionArgs, NullValueArgs, OpcodesArgs,
+    OpenArgs, OutputModeArgs, SchemaArgs, SetOutputArgs, TablesArgs, TimerArgs,
 };
 use clap::Parser;
 use import::ImportArgs;
@@ -72,6 +72,9 @@ pub enum Command {
     /// List vfs modules available
     #[command(name = "vfslist", display_name = ".vfslist")]
     ListVfs,
+    /// Show names of indexes
+    #[command(name = "indexes", display_name = ".indexes")]
+    ListIndexes(IndexesArgs),
     #[command(name = "timer", display_name = ".timer")]
     Timer(TimerArgs),
 }

cli/input.rs

@@ -218,6 +218,8 @@ pub const AFTER_HELP_MSG: &str = r#"Usage Examples:
 
 13. To list all available VFS:
    .listvfs
+14. To show names of indexes:
+   .indexes ?TABLE?
 
 Note:
 - All SQL commands must end with a semicolon (;).