From 7eab5041269cc2aef5974a06d4e63836833955aa Mon Sep 17 00:00:00 2001
From: Damien Elmes <gpg@ankiweb.net>
Date: Tue, 17 Mar 2020 13:41:56 +1000
Subject: [PATCH] add field_at_index() sql func

---
 rslib/Cargo.toml             |  4 ++--
 rslib/src/search/searcher.rs |  2 --
 rslib/src/storage/sqlite.rs  | 15 +++++++++++++++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/rslib/Cargo.toml b/rslib/Cargo.toml
index 7250b185c..58e5d5c90 100644
--- a/rslib/Cargo.toml
+++ b/rslib/Cargo.toml
@@ -40,10 +40,10 @@ serde_repr = "0.1.5"
 num_enum = "0.4.2"
 
 [target.'cfg(target_vendor="apple")'.dependencies]
-rusqlite = { version = "0.21.0", features = ["trace"] }
+rusqlite = { version = "0.21.0", features = ["trace", "functions"] }
 
 [target.'cfg(not(target_vendor="apple"))'.dependencies]
-rusqlite = { version = "0.21.0", features = ["trace", "bundled"] }
+rusqlite = { version = "0.21.0", features = ["trace", "functions", "bundled"] }
 
 [target.'cfg(linux)'.dependencies]
 reqwest = { version = "0.10.1", features = ["json", "native-tls-vendored"] }
diff --git a/rslib/src/search/searcher.rs b/rslib/src/search/searcher.rs
index 188aff410..9a2c67e96 100644
--- a/rslib/src/search/searcher.rs
+++ b/rslib/src/search/searcher.rs
@@ -216,7 +216,6 @@ fn write_note_type(ctx: &mut SearchContext, _notetype: &str) {
 }
 
 // fixme: need note type manager
-// fixme: need field_at_index()
 fn write_single_field(ctx: &mut SearchContext, field: &str, val: &str) {
     let _ = field;
     let fields = vec![(0, 0)]; // fixme: get list of (ntid, ordinal)
@@ -240,7 +239,6 @@ fn write_single_field(ctx: &mut SearchContext, field: &str, val: &str) {
     write!(ctx.sql, ")").unwrap();
 }
 
-// fixme: need field_at_index()
 fn write_dupes(ctx: &mut SearchContext, ntid: &ObjID, text: &str) {
     let csum = field_checksum(text);
     write!(
diff --git a/rslib/src/storage/sqlite.rs b/rslib/src/storage/sqlite.rs
index 886a8f801..967e79727 100644
--- a/rslib/src/storage/sqlite.rs
+++ b/rslib/src/storage/sqlite.rs
@@ -36,11 +36,26 @@ fn open_or_create_collection_db(path: &Path) -> Result<Connection> {
     db.pragma_update(None, "cache_size", &(-40 * 1024))?;
     db.pragma_update(None, "legacy_file_format", &false)?;
     db.pragma_update(None, "journal", &"wal")?;
+
     db.set_prepared_statement_cache_capacity(50);
 
+    add_field_index_function(&db)?;
+
     Ok(db)
 }
 
+/// Adds sql function field_at_index(flds, index)
+/// to split provided fields and return field at zero-based index.
+/// If out of range, returns empty string.
+fn add_field_index_function(db: &Connection) -> Result<()> {
+    db.create_scalar_function("field_at_index", 2, true, |ctx| {
+        let mut fields = ctx.get_raw(0).as_str()?.split('\x1f');
+        let idx: u16 = ctx.get(1)?;
+        Ok(fields.nth(idx as usize).unwrap_or("").to_string())
+    })
+    .map_err(Into::into)
+}
+
 /// Fetch schema version from database.
 /// Return (must_create, version)
 fn schema_version(db: &Connection) -> Result<(bool, u8)> {