@@ -17,6 +17,8 @@ final class QueryViewModel {
1717 // Build search texts asynchronously
1818 searchTextTask?.cancel()
1919 cachedSearchTexts = []
20+ searchTextGeneration &+= 1
21+ let generation = searchTextGeneration
2022 // Apply the current filter immediately using the inline fallback path
2123 // (the cache was just invalidated). Calling updateFilteredResults()
2224 // rather than `filteredResults = results` avoids briefly showing
@@ -36,6 +38,12 @@ final class QueryViewModel {
3638 }
3739 }.value
3840 guard let self, !Task.isCancelled else { return }
41+ // Reject a stale write: if `results` was reassigned while this task
42+ // was awaiting, a newer didSet bumped the generation. Task.isCancelled
43+ // alone isn't sufficient because two re-queries producing result sets
44+ // of identical count would otherwise let this stale, same-length
45+ // cachedSearchTexts slip past updateFilteredResults's count guard.
46+ guard generation == self.searchTextGeneration else { return }
3947 self.cachedSearchTexts = texts
4048 if !self.filterText.isEmpty {
4149 self.updateFilteredResults()
@@ -45,12 +53,35 @@ final class QueryViewModel {
4553 }
4654 private var cachedSearchTexts: [String] = []
4755 private var searchTextTask: Task<Void, Never>?
56+ /// Bumped on every `results` reassignment so the async search-text builder can
57+ /// detect it was superseded and drop a stale write (see results.didSet).
58+ private var searchTextGeneration = 0
4859 var columns: [String] = []
4960 var columnOrder: [String] = []
5061 var hiddenColumns: Set<String> = []
62+ /// The full persisted set of hidden columns for the current stream, including
63+ /// ones absent from the current result. Hiding a column drops it from the
64+ /// SELECT list, so it's missing from the very next result and `hiddenColumns`
65+ /// (only the columns present) forgets it — the next save would then erase the
66+ /// preference. This keeps the intent, mirroring LiveTailViewModel.
67+ private(set) var savedHiddenColumns: Set<String> = []
68+ /// The persisted column order including columns absent from the current
69+ /// result (the order counterpart of `savedHiddenColumns`), so saving doesn't
70+ /// drop a hidden column's position and it returns to its place when shown.
71+ private var savedColumnOrder: [String] = []
5172 var autoHiddenColumns: Set<String> = []
5273 /// Column config from a saved query, applied on next query execution.
5374 var pendingColumnConfig: ColumnConfiguration?
75+
76+ /// The connection and stream the editor text and results belong to. The view
77+ /// model outlives QueryView (switching tabs keeps the query), so the view
78+ /// compares this on appear to catch a stream/server change made while another
79+ /// tab was showing.
80+ struct BoundContext: Equatable {
81+ let connectionID: UUID?
82+ let stream: String
83+ }
84+ var boundContext: BoundContext?
5485 private var currentStream: String?
5586 var isLoading = false
5687 var errorMessage: String?
@@ -68,10 +99,23 @@ final class QueryViewModel {
6899 var schemaFields: [SchemaField] = []
69100 /// The stream of the most recent `loadSchema` call, used to drop a stale
70101 /// in-flight response when the user rapidly switches streams.
71− private var latestSchemaStream: String?
102+ private(set) var latestSchemaStream: String?
103+ /// The stream of the most recent `executeQuery` call. Defense-in-depth
104+ /// alongside `queryGeneration`/task cancellation: drops a stale in-flight
105+ /// query response if a newer query for a different stream supersedes it
106+ /// without going through the normal cancel path.
107+ private var latestQueryStream: String?
72108
73109 // Query task for cancellation
74110 private var queryTask: Task<Void, Never>?
111+ /// Bumped at the start of every `executeQuery`. The task captures this value
112+ /// and only clears `isLoading` on exit if it's still the active query — so a
113+ /// superseded query's late cleanup doesn't drop the loading indicator that
114+ /// the newer query set. Without this, `isLoading = false` had to live in
115+ /// every caller of `cancel()` (cancelQuery, clearResults, superseding
116+ /// executeQuery) and a future cancel path that forgot to set it would wedge
117+ /// the spinner indefinitely.
118+ private var queryGeneration = 0
75119
76120 // Time range
77121 var timeRangeOption: TimeRangeOption = .last1Hour
@@ -168,9 +212,16 @@ final class QueryViewModel {
168212 return columnOrder.filter { !allHidden.contains($0) }
169213 }
170214
215+ /// Whether any column is hidden — including saved-hidden columns that aren't
216+ /// in the current result, which "Show All" can bring back.
217+ var hasHiddenColumns: Bool {
218+ !hiddenColumns.isEmpty || !autoHiddenColumns.isEmpty || !savedHiddenColumns.isEmpty
219+ }
220+
171221 func toggleColumnVisibility(_ column: String) {
172222 if hiddenColumns.contains(column) {
173223 hiddenColumns.remove(column)
224+ savedHiddenColumns.remove(column)
174225 } else if autoHiddenColumns.contains(column) {
175226 autoHiddenColumns.remove(column)
176227 } else {
@@ -179,6 +230,7 @@ final class QueryViewModel {
179230 let visibleCount = columnOrder.count - allHidden.count
180231 if visibleCount > 1 {
181232 hiddenColumns.insert(column)
233+ savedHiddenColumns.insert(column)
182234 }
183235 }
184236 saveColumnConfig()
@@ -187,6 +239,7 @@ final class QueryViewModel {
187239
188240 func showAllColumns() {
189241 hiddenColumns.removeAll()
242+ savedHiddenColumns.removeAll()
190243 autoHiddenColumns.removeAll()
191244 saveColumnConfig()
192245 updateSQLColumns()
@@ -216,32 +269,116 @@ final class QueryViewModel {
216269
217270 func resetColumnConfig() {
218271 columnOrder = columns
272+ savedColumnOrder = []
219273 hiddenColumns.removeAll()
274+ savedHiddenColumns.removeAll()
220275 autoHiddenColumns.removeAll()
221276 saveColumnConfig()
222277 updateSQLColumns()
223278 }
224279
225− /// Rewrites the SELECT clause of `sqlQuery` to reflect the current `visibleColumns`.
280+ /// Rewrites the SELECT clause of `sqlQuery` to reflect the user's column
281+ /// choices (order and hidden columns; auto-hidden columns stay display-only).
226282 func updateSQLColumns() {
227− guard let range = SQLTokenizer.selectColumnListRange(in: sqlQuery) else { return }
228−
229− let visible = visibleColumns
283+ guard let range = SQLTokenizer.selectColumnListRange(in: sqlQuery),
284+ let currentList = Self.parseColumnList(sqlQuery[range]) else { return }
285+
286+ // Project the user's choices only. `autoHiddenColumns` is a display
287+ // heuristic for the current rows (the field is empty in all of them);
288+ // baking it into the SQL would stop the field from ever being fetched
289+ // again, even for a time range where it has values.
290+ let visible = columnOrder.filter { !hiddenColumns.contains($0) }
230291 guard !visible.isEmpty else { return }
231292
293+ // Columns an explicit list names that aren't in the results: Parseable
294+ // omits all-null fields from query JSON, so a sparse listed field can be
295+ // missing from `columns`. Keep it (unless the user hid it) rather than
296+ // silently dropping it from the SELECT on the next rewrite.
297+ var listedButAbsent: [String] = []
298+ var excludesHiddenColumn = false
299+ if case .identifiers(let names) = currentList {
300+ let present = Set(columns)
301+ listedButAbsent = names.filter { !present.contains($0) && !savedHiddenColumns.contains($0) }
302+ // A column the user hid is absent from these results precisely
303+ // because this list was narrowed to exclude it.
304+ excludesHiddenColumn = !savedHiddenColumns.isSubset(of: present)
305+ }
306+
232307 let newColumnList: String
233308 // Use `*` whenever every column is visible, regardless of display order —
234309 // reordering columns (a set-preserving permutation) must not pin the query
235− // to an explicit snapshot that hides newly-appearing fields on re-query.
236− if visible.count == columns.count && Set(visible) == Set(columns) {
310+ // to an explicit snapshot that hides newly-appearing fields on re-query —
311+ // unless the list is explicit because it leaves out a hidden column, which
312+ // `*` would fetch again.
313+ if !excludesHiddenColumn && visible.count == columns.count && Set(visible) == Set(columns) {
237314 newColumnList = "*"
238315 } else {
239− newColumnList = visible.map { Self.escapeSQLIdentifier($0) }.joined(separator: ", ")
316+ newColumnList = (visible + listedButAbsent).map { Self.escapeSQLIdentifier($0) }.joined(separator: ", ")
240317 }
241318
242319 sqlQuery.replaceSubrange(range, with: newColumnList)
243320 }
244321
322+ enum ColumnListShape: Equatable {
323+ case star
324+ /// Plain column references, as the column names they resolve to.
325+ case identifiers([String])
326+ }
327+
328+ /// Parses a SELECT list the column manager can regenerate without changing
329+ /// what the query computes: `*`, or a comma-separated list of plain column
330+ /// references. Anything else — aggregates, expressions, aliases
331+ /// (`count(*) AS n`), qualified names — returns nil: rewriting it with `*` or
332+ /// bare result keys would break the query, so the column manager then only
333+ /// hides/reorders client-side.
334+ nonisolated static func parseColumnList(_ list: Substring) -> ColumnListShape? {
335+ let tokens = SQLTokenizer.tokenize(String(list)).filter { !$0.kind.isTrivia }
336+ if tokens.count == 1, tokens[0].kind == .star { return .star }
337+ guard tokens.count % 2 == 1 else { return nil }
338+ var names: [String] = []
339+ for (index, token) in tokens.enumerated() {
340+ if index % 2 == 1 {
341+ guard token.kind == .comma else { return nil }
342+ continue
343+ }
344+ switch token.kind {
345+ // DataFusion folds unquoted identifiers to lowercase.
346+ case .identifier(let name): names.append(name.lowercased())
347+ case .quotedIdentifier(let name): names.append(name)
348+ default: return nil
349+ }
350+ }
351+ return .identifiers(names)
352+ }
353+
354+ /// Inserts `newColumns` into `order`, placing each one that appears in
355+ /// `reference` (a saved order) right after its nearest saved predecessor
356+ /// that's already placed — or first if none is — and appending the rest.
357+ /// Used to keep the positions of columns that are absent for a while.
358+ nonisolated static func mergedColumnOrder(
359+ _ order: [String], inserting newColumns: [String], reference: [String]
360+ ) -> [String] {
361+ var result = order
362+ let referenceIndex = Dictionary(reference.enumerated().map { ($1, $0) }, uniquingKeysWith: { first, _ in first })
363+ let pending = newColumns.filter { referenceIndex[$0] == nil }
364+ let positioned = newColumns
365+ .filter { referenceIndex[$0] != nil }
366+ .sorted { referenceIndex[$0]! < referenceIndex[$1]! }
367+ for column in positioned where !result.contains(column) {
368+ let savedIndex = referenceIndex[column]!
369+ let predecessor = reference[..<savedIndex].reversed().first { result.contains($0) }
370+ if let predecessor, let position = result.firstIndex(of: predecessor) {
371+ result.insert(column, at: position + 1)
372+ } else {
373+ result.insert(column, at: 0)
374+ }
375+ }
376+ for column in pending where !result.contains(column) {
377+ result.append(column)
378+ }
379+ return result
380+ }
381+
245382 // MARK: - Column Configuration Persistence
246383
247384 struct ColumnConfiguration: Codable {
@@ -255,7 +392,16 @@ final class QueryViewModel {
255392
256393 private func saveColumnConfig() {
257394 guard let stream = currentStream else { return }
258− let config = ColumnConfiguration(order: columnOrder, hidden: hiddenColumns)
395+ // Persist the full intended hidden set and order, not just the currently
396+ // present columns (see `savedHiddenColumns` / `savedColumnOrder`).
397+ let present = Set(columnOrder)
398+ let order = Self.mergedColumnOrder(
399+ columnOrder,
400+ inserting: savedColumnOrder.filter { !present.contains($0) },
401+ reference: savedColumnOrder
402+ )
403+ savedColumnOrder = order
404+ let config = ColumnConfiguration(order: order, hidden: savedHiddenColumns.union(hiddenColumns))
259405 if let data = try? JSONEncoder().encode(config) {
260406 UserDefaults.standard.set(data, forKey: Self.columnConfigKey(for: stream))
261407 }
@@ -284,7 +430,9 @@ final class QueryViewModel {
284430
285431 guard let config else {
286432 columnOrder = extractedColumns
433+ savedColumnOrder = []
287434 hiddenColumns = []
435+ savedHiddenColumns = []
288436 return
289437 }
290438
@@ -297,6 +445,8 @@ final class QueryViewModel {
297445 merged.append(col)
298446 }
299447 columnOrder = merged
448+ savedColumnOrder = config.order
449+ savedHiddenColumns = config.hidden
300450 hiddenColumns = config.hidden.intersection(extractedSet)
301451
302452 // The `visibleCount > 1` guard in toggleColumnVisibility only covers
@@ -390,6 +540,13 @@ final class QueryViewModel {
390540
391541 // Cancel any in-flight query
392542 queryTask?.cancel()
543+ // Bump the generation so the in-flight task's cleanup can detect that
544+ // it has been superseded and skip its `isLoading = false` (which would
545+ // otherwise race with the `isLoading = true` below and briefly drop
546+ // the loading indicator during this query).
547+ queryGeneration &+= 1
548+ let generation = queryGeneration
549+ latestQueryStream = stream
393550
394551 isLoading = true
395552 errorMessage = nil
@@ -398,6 +555,16 @@ final class QueryViewModel {
398555 let startTime = CFAbsoluteTimeGetCurrent()
399556
400557 let task = Task {
558+ // Always clear the spinner on exit when this is still the active
559+ // query. The defer runs on every path (success, error, and the
560+ // cancellation cases that previously returned before reaching the
561+ // trailing `isLoading = false`), so the spinner can never wedge
562+ // even if a new cancel path is added without resetting it.
563+ defer {
564+ if generation == queryGeneration {
565+ isLoading = false
566+ }
567+ }
401568 do {
402569 try Task.checkCancellation()
403570 let queryResults = try await client.query(sql: sql, startTime: startDate, endTime: endDate)
@@ -407,6 +574,9 @@ final class QueryViewModel {
407574 // cancellation landing just after the check above would otherwise
408575 // let a stale query clobber the newer one's results/columns.
409576 guard !Task.isCancelled else { return }
577+ // Drop the response if a newer query (possibly for a different
578+ // stream) has since been launched without cancelling this task.
579+ guard latestQueryStream == stream else { return }
410580
411581 results = queryResults
412582 // Drop any prior row selection: the new result set reassigns row
@@ -416,9 +586,13 @@ final class QueryViewModel {
416586 queryDuration = CFAbsoluteTimeGetCurrent() - startTime
417587 resultCount = results.count
418588
419− // Detect if results were likely truncated (only meaningful
420− // for auto-generated queries where we control the LIMIT)
421− resultsTruncated = usedAutoLimit && results.count == limit
589+ // Detect if results were likely truncated. We know the cap for
590+ // auto-generated queries; for user-entered SQL (which includes the
591+ // default query `setDefaultQuery` writes into the editor — the common
592+ // stream-selection path), parse a trailing `LIMIT n` so the indicator
593+ // still fires when the row count lands exactly on the limit.
594+ let effectiveLimit = usedAutoLimit ? limit : Self.trailingLimit(in: sql)
595+ resultsTruncated = effectiveLimit.map { results.count == $0 } ?? false
422596
423597 // Extract columns in a single pass, with priority fields first,
424598 // then apply any saved column configuration for this stream
@@ -445,12 +619,23 @@ final class QueryViewModel {
445619 return
446620 } catch {
447621 guard !Task.isCancelled else { return }
622+ // Same supersession guard as the success path: a stale failed
623+ // query must not clobber a newer query's state.
624+ guard latestQueryStream == stream else { return }
448625 errorMessage = ParseableError.userFriendlyMessage(for: error)
449626 if let serverError = error as? ParseableError,
450627 case .serverError(_, let msg) = serverError,
451− let pos = SQLErrorPosition.parse(from: msg) {
628+ let pos = SQLErrorPosition.parse(from: msg),
629+ sqlQuery == sql {
630+ // The server's line/column is relative to the *submitted* SQL.
631+ // Only map it back into the editor when the editor still holds
632+ // that same text — if the user edited the query while it was in
633+ // flight, the position no longer corresponds to what's displayed
634+ // and would underline an unrelated span. (`sqlQuery`'s didSet
635+ // already cleared errorRange on that edit, so leaving it nil here
636+ // keeps the editor unmarked.)
452637 errorRange = SQLTokenizer.errorHighlightRange(
453− line: pos.line, column: pos.column, in: sqlQuery
638+ line: pos.line, column: pos.column, in: sql
454639 )
455640 }
456641 results = []
@@ -460,10 +645,10 @@ final class QueryViewModel {
460645 // report stale column names after the failure.
461646 columnOrder = []
462647 hiddenColumns = []
648+ savedHiddenColumns = []
649+ savedColumnOrder = []
463650 autoHiddenColumns = []
464651 }
465−
466− isLoading = false
467652 }
468653 queryTask = task
469654 await task.value
@@ -628,6 +813,8 @@ final class QueryViewModel {
628813 columns = []
629814 columnOrder = []
630815 hiddenColumns = []
816+ savedHiddenColumns = []
817+ savedColumnOrder = []
631818 autoHiddenColumns = []
632819 currentStream = nil
633820 resultCount = 0
@@ -637,6 +824,11 @@ final class QueryViewModel {
637824 errorRange = nil
638825 resultsTruncated = false
639826 schemaFields = []
827+ // Keep the stream trackers consistent with the cleared schema/results so
828+ // a later reload guard never sees a non-nil stream paired with empty data.
829+ latestSchemaStream = nil
830+ latestQueryStream = nil
831+ boundContext = nil
640832 }
641833
642834 /// Modifies `sqlQuery` to add a column-value filter condition.
@@ -646,75 +838,139 @@ final class QueryViewModel {
646838 let condition: String
647839 if let value, value != .null {
648840 let literal = value.sqlLiteral
649− condition = exclude ? "\(escapedCol) <> \(literal)" : "\(escapedCol) = \(literal)"
841+ // Exclude with `IS DISTINCT FROM`, not `<>`: under SQL's three-valued
842+ // logic `NULL <> 'x'` is NULL, so `<>` also dropped every row where the
843+ // column is missing/NULL — common for sparse fields — which "exclude
844+ // this value" doesn't ask for (the live-tail exclude keeps them too).
845+ condition = exclude
846+ ? "\(escapedCol) IS DISTINCT FROM \(literal)"
847+ : "\(escapedCol) = \(literal)"
650848 } else {
651849 condition = exclude ? "\(escapedCol) IS NOT NULL" : "\(escapedCol) IS NULL"
652850 }
653851
654− var sql = sqlQuery.trimmingCharacters(in: .whitespacesAndNewlines)
852+ let sql = sqlQuery.trimmingCharacters(in: .whitespacesAndNewlines)
655853 if sql.isEmpty { return }
656854
657855 // Locate the top-level WHERE and the first trailing clause using the
658856 // tokenizer rather than a raw regex, so keywords inside quoted
659857 // identifiers, string literals, comments, or subqueries are ignored.
660− let tailKeywords: Set<String> = ["ORDER", "GROUP", "HAVING", "LIMIT", "OFFSET"]
858+ let tokens = SQLTokenizer.tokenize(sql)
661859 var depth = 0
662− var whereEnd: String.Index?
663− var tailStart: String.Index?
860+ // WHERE and the trailing clauses only follow the top-level FROM. Keywords
861+ // before it belong to the SELECT list — e.g. a field named `offset` or
862+ // `limit` (which the tokenizer reports as keywords) — and must not be
863+ // mistaken for clause starts.
864+ var fromSeen = false
865+ var whereIndex: Int?
866+ var tailIndex: Int?
664867 // Track whether the existing WHERE body has a top-level OR — only then does
665868 // AND-ing a new condition need parentheses to preserve precedence.
666869 var bodyHasTopLevelOr = false
667− for token in SQLTokenizer.tokenize(sql) {
870+ // The last token that is actual SQL — not whitespace, a comment, or a
871+ // statement-terminating `;`. New text is spliced in right after such
872+ // tokens (never at the raw end of the string), so a trailing `;` or a
873+ // trailing `-- comment` stays at the end instead of swallowing the
874+ // appended condition: `... LIMIT 10;` must not become `... LIMIT 10; WHERE`,
875+ // and `... -- note` must not become `... -- note WHERE <commented out>`.
876+ func isSignificant(_ token: SQLTokenizer.Token) -> Bool {
877+ !token.kind.isTrivia && token.kind != .other(";")
878+ }
879+ func nextSignificantKind(after index: Int) -> SQLTokenizer.TokenKind? {
880+ tokens[(index + 1)...].first(where: { isSignificant($0) })?.kind
881+ }
882+ // Whether the keyword at `index` actually opens a trailing clause. ORDER and
883+ // GROUP must be followed by BY (so `WITHIN GROUP (…)` or a column named
884+ // `order` doesn't count), and LIMIT/OFFSET by their row count (so a column
885+ // named `offset` in `WHERE offset > 5` doesn't cut the WHERE body short).
886+ func startsTrailingClause(_ keyword: String, at index: Int) -> Bool {
887+ switch keyword {
888+ case "ORDER", "GROUP":
889+ return nextSignificantKind(after: index) == .keyword("BY")
890+ case "LIMIT", "OFFSET":
891+ if case .number = nextSignificantKind(after: index) { return true }
892+ return false
893+ case "HAVING":
894+ return true
895+ default:
896+ return false
897+ }
898+ }
899+ var lastSignificant: Int?
900+ for (idx, token) in tokens.enumerated() {
901+ if isSignificant(token) { lastSignificant = idx }
668902 switch token.kind {
669903 case .leftParen:
670904 depth += 1
671905 case .rightParen:
672906 depth = max(0, depth - 1)
673− case .keyword(let kw) where depth == 0:
674− if kw == "WHERE", whereEnd == nil {
675− whereEnd = token.range.upperBound
676− } else if tailKeywords.contains(kw), tailStart == nil {
677− tailStart = token.range.lowerBound
678− } else if kw == "OR", whereEnd != nil, tailStart == nil {
907+ case .keyword("FROM") where depth == 0:
908+ fromSeen = true
909+ case .keyword(let kw) where depth == 0 && fromSeen:
910+ if kw == "WHERE", whereIndex == nil {
911+ whereIndex = idx
912+ // A trailing clause seen *before* the WHERE (e.g. the GROUP BY of
913+ // the first SELECT in `... GROUP BY a UNION ALL SELECT ... WHERE`)
914+ // doesn't end this WHERE's body. Keeping it would make the body
915+ // range run backwards (a trapping `Range`), so look for the
916+ // body's end afresh after the WHERE.
917+ tailIndex = nil
918+ } else if tailIndex == nil, startsTrailingClause(kw, at: idx) {
919+ tailIndex = idx
920+ } else if kw == "OR", whereIndex != nil, tailIndex == nil {
679921 bodyHasTopLevelOr = true
680922 }
681923 default:
682924 break
683925 }
684926 }
685−
686− if let whereEnd {
687− // Parenthesize the existing WHERE body before AND-ing the new
688− // condition only when it has a top-level OR, otherwise the OR
689− // silently changes meaning: `WHERE a = 1 OR b = 2` would become
690− // `WHERE a = 1 OR b = 2 AND c = 3`, which SQL binds as
691− // `a = 1 OR (b = 2 AND c = 3)` rather than the intended
692− // `(a = 1 OR b = 2) AND c = 3`. A body without a top-level OR is
693− // left un-parenthesized so simple filters stay readable.
694− let bodyEnd = tailStart ?? sql.endIndex
695− let head = sql[..<whereEnd]
696− let body = sql[whereEnd..<bodyEnd].trimmingCharacters(in: .whitespacesAndNewlines)
697− let tail = sql[bodyEnd...].trimmingCharacters(in: .whitespacesAndNewlines)
698− // An empty WHERE body (e.g. a half-written `... WHERE` with no
699− // condition yet, or `WHERE` immediately followed by ORDER/GROUP/
700− // LIMIT) would otherwise produce `WHERE AND <condition>` — a
701− // dangling AND with no left operand. Drop the AND in that case.
702− if body.isEmpty {
703− sql = "\(head) \(condition)"
927+ // Nothing but comments/semicolons — there's no statement to filter.
928+ guard let lastSignificant else { return }
929+
930+ // Each branch rebuilds the query from slices of the original text, keeping
931+ // the user's line breaks: joining pieces with single spaces would pull the
932+ // text after a `-- comment` onto the comment's line and comment it out.
933+ // Text spliced directly in front of another token (`(a = 1)ORDER BY`) needs
934+ // a space so the two don't fuse (`... IS NULLORDER BY`).
935+ func separated(_ rest: Substring) -> String {
936+ guard let next = rest.first, !next.isWhitespace, next != ";" else { return String(rest) }
937+ return " " + rest
938+ }
939+ if let whereIndex {
940+ // The WHERE body runs up to the first trailing clause, or to the end
941+ // of the statement. Only its significant tokens bound the splice, so a
942+ // comment between the body and ORDER BY stays after the new condition.
943+ let bodyEndIndex = tailIndex ?? (lastSignificant + 1)
944+ let bodyIndices = (whereIndex + 1)..<bodyEndIndex
945+ if let first = bodyIndices.first(where: { isSignificant(tokens[$0]) }),
946+ let last = bodyIndices.last(where: { isSignificant(tokens[$0]) }) {
947+ // Parenthesize the existing WHERE body before AND-ing the new
948+ // condition only when it has a top-level OR, otherwise the OR
949+ // silently changes meaning: `WHERE a = 1 OR b = 2` would become
950+ // `WHERE a = 1 OR b = 2 AND c = 3`, which SQL binds as
951+ // `a = 1 OR (b = 2 AND c = 3)` rather than the intended
952+ // `(a = 1 OR b = 2) AND c = 3`. A body without a top-level OR is
953+ // left un-parenthesized so simple filters stay readable.
954+ let bodyStart = tokens[first].range.lowerBound
955+ let bodyEnd = tokens[last].range.upperBound
956+ let body = sql[bodyStart..<bodyEnd]
957+ let wrappedBody = bodyHasTopLevelOr ? "(\(body))" : String(body)
958+ sqlQuery = "\(sql[..<bodyStart])\(wrappedBody) AND \(condition)\(separated(sql[bodyEnd...]))"
704959 } else {
705− let wrappedBody = bodyHasTopLevelOr ? "(\(body))" : body
706− sql = "\(head) \(wrappedBody) AND \(condition)"
707− }
708− if !tail.isEmpty {
709− sql += " \(tail)"
960+ // An empty WHERE body (e.g. a half-written `... WHERE` with no
961+ // condition yet, or `WHERE` immediately followed by ORDER/GROUP/
962+ // LIMIT) would otherwise produce `WHERE AND <condition>` — a
963+ // dangling AND with no left operand. Drop the AND in that case.
964+ let whereEnd = tokens[whereIndex].range.upperBound
965+ sqlQuery = "\(sql[..<whereEnd]) \(condition)\(separated(sql[whereEnd...]))"
710966 }
711− } else if let tailStart {
712− sql.insert(contentsOf: "WHERE \(condition) ", at: tailStart)
967+ } else if let tailIndex {
968+ let tailStart = tokens[tailIndex].range.lowerBound
969+ sqlQuery = "\(sql[..<tailStart])WHERE \(condition) \(sql[tailStart...])"
713970 } else {
714− sql += " WHERE \(condition)"
971+ let statementEnd = tokens[lastSignificant].range.upperBound
972+ sqlQuery = "\(sql[..<statementEnd]) WHERE \(condition)\(separated(sql[statementEnd...]))"
715973 }
716−
717− sqlQuery = sql
718974 }
719975
720976 /// Sets the default query for the given stream, returning `true` if the
@@ -742,9 +998,26 @@ final class QueryViewModel {
742998 "\"\(identifier.replacingOccurrences(of: "\"", with: "\"\""))\""
743999 }
7441000
1001+ /// Extracts the row cap from a trailing `LIMIT n` clause (tolerating a trailing
1002+ /// semicolon/whitespace), used to detect when a result set was truncated.
1003+ /// Returns nil when there's no recognizable trailing `LIMIT` — e.g. when the
1004+ /// query uses `LIMIT n OFFSET m` — so we never report a false truncation.
1005+ nonisolated static func trailingLimit(in sql: String) -> Int? {
1006+ let pattern = #"(?i)\bLIMIT\s+(\d+)\s*;?\s*$"#
1007+ guard let regex = try? NSRegularExpression(pattern: pattern) else { return nil }
1008+ let range = NSRange(sql.startIndex..<sql.endIndex, in: sql)
1009+ guard let match = regex.firstMatch(in: sql, range: range),
1010+ let numberRange = Range(match.range(at: 1), in: sql) else { return nil }
1011+ return Int(sql[numberRange])
1012+ }
1013+
7451014 // MARK: - Query History
7461015
7471016 private func addToHistory(_ entry: QueryHistoryEntry) {
1017+ // Start from what's persisted, not this instance's copy: a model created
1018+ // earlier (e.g. one whose query finished after a reconnect replaced it)
1019+ // would otherwise overwrite newer entries saved by the current one.
1020+ queryHistory = Self.loadHistory()
7481021 // Deduplicate consecutive identical queries
7491022 if queryHistory.first?.sql == entry.sql { return }
7501023 queryHistory.insert(entry, at: 0)