aliases are normalized and used in normalized state, but nonnormalized aliases contain everything

common/Cargo.toml

@@ -21,6 +21,9 @@ serde = { version = "1.0.228", features = ["derive"] }
 tantivy = { workspace = true, optional = true }
 serde_json.workspace = true
 tonic-prost = "0.14.6"
+unicode-normalization.workspace = true
+unicode-properties.workspace = true
+icu_casemap.workspace = true
 
 [build-dependencies]
 tonic-build = { version = "0.14.6" }

common/proto/table_definition.proto

@@ -147,7 +147,12 @@ message GeneratedColumnAlias {
   // ignored, so a typo cannot pass silently.
   string generated_name = 1;
 
-  // What the column should be called instead. Same rules as any column name.
+  // What the column should be called instead. Preserved exactly for display.
+  // Aliases may contain Unicode letters, numbers, spaces, punctuation and
+  // symbols, but not leading/trailing whitespace or control characters, and
+  // are limited to 63 UTF-8 bytes. Uniqueness and lookup use a compatibility-
+  // normalized, Unicode-case-folded key that collapses whitespace and ignores
+  // emoji while keeping punctuation significant.
   string alias = 2;
 }
 

common/src/alias.rs

@@ -0,0 +1,92 @@
+use icu_casemap::CaseMapper;
+use unicode_normalization::UnicodeNormalization;
+use unicode_properties::emoji::{
+    is_emoji_presentation_selector, is_tag_character, is_text_presentation_selector, is_zwj,
+};
+use unicode_properties::{GeneralCategoryGroup, UnicodeEmoji, UnicodeGeneralCategory};
+
+/// PostgreSQL's identifier limit. Display aliases are used as result-column
+/// labels in a few query paths, so the limit is measured in UTF-8 bytes.
+pub const MAX_ALIAS_BYTES: usize = 63;
+
+/// Whether a display alias contains control, formatting, private-use, or
+/// unassigned characters that should never be persisted as visible naming.
+pub fn has_disallowed_alias_characters(alias: &str) -> bool {
+    alias
+        .chars()
+        .any(|character| {
+            character.general_category_group() == GeneralCategoryGroup::Other
+                && !is_zwj(character)
+                && !is_emoji_presentation_selector(character)
+                && !is_text_presentation_selector(character)
+                && !is_tag_character(character)
+        })
+}
+
+/// The hidden key used to compare and resolve public column aliases.
+///
+/// Display spelling is never changed. Compatibility-equivalent spelling and
+/// case compare alike, whitespace runs compare as one space, and emoji are
+/// ignored. Letters, marks, numbers, punctuation and useful non-emoji symbols
+/// remain significant.
+pub fn canonical_alias(alias: &str) -> String {
+    let compatible = alias.nfkc().collect::<String>();
+    let folded = CaseMapper::new().fold_string(&compatible).into_owned();
+    let mut canonical = String::new();
+    let mut pending_space = false;
+
+    for character in folded.chars() {
+        match character.general_category_group() {
+            GeneralCategoryGroup::Letter
+            | GeneralCategoryGroup::Mark
+            | GeneralCategoryGroup::Number
+            | GeneralCategoryGroup::Punctuation => {
+                if pending_space && !canonical.is_empty() {
+                    canonical.push(' ');
+                }
+                pending_space = false;
+                canonical.push(character);
+            }
+            GeneralCategoryGroup::Symbol if !character.is_emoji_char() => {
+                if pending_space && !canonical.is_empty() {
+                    canonical.push(' ');
+                }
+                pending_space = false;
+                canonical.push(character);
+            }
+            GeneralCategoryGroup::Separator => {
+                pending_space = !canonical.is_empty();
+            }
+            GeneralCategoryGroup::Symbol | GeneralCategoryGroup::Other => {}
+        }
+    }
+
+    canonical.nfc().collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn aliases_compare_by_compatibility_case_and_without_emoji() {
+        assert_eq!(canonical_alias("Apple"), "apple");
+        assert_eq!(canonical_alias("APPLE🙂"), "apple");
+        assert_eq!(canonical_alias("Ａｐｐｌｅ"), "apple");
+        assert_eq!(canonical_alias("Straße"), canonical_alias("STRASSE"));
+        assert_eq!(canonical_alias("Apple👨‍👩‍👧"), "apple");
+        assert!(!has_disallowed_alias_characters("Apple👨‍👩‍👧"));
+    }
+
+    #[test]
+    fn punctuation_and_useful_symbols_remain_significant() {
+        assert_eq!(canonical_alias("Apple."), "apple.");
+        assert_eq!(canonical_alias("Apple!"), "apple!");
+        assert_eq!(canonical_alias("Price €"), "price €");
+    }
+
+    #[test]
+    fn whitespace_runs_compare_as_one_space() {
+        assert_eq!(canonical_alias("First   Name"), "first name");
+    }
+}

common/src/lib.rs

@@ -2,6 +2,7 @@
 
 #[cfg_attr(not(feature = "tantivy"), path = "search_light.rs")]
 pub mod search;
+pub mod alias;
 pub mod decimal;
 pub mod grpc_error;
 pub mod money;

common/src/proto/komp_ac.table_definition.rs

@@ -90,7 +90,12 @@ pub struct GeneratedColumnAlias {
     /// ignored, so a typo cannot pass silently.
     #[prost(string, tag = "1")]
     pub generated_name: ::prost::alloc::string::String,
-    /// What the column should be called instead. Same rules as any column name.
+    /// What the column should be called instead. Preserved exactly for display.
+    /// Aliases may contain Unicode letters, numbers, spaces, punctuation and
+    /// symbols, but not leading/trailing whitespace or control characters, and
+    /// are limited to 63 UTF-8 bytes. Uniqueness and lookup use a compatibility-
+    /// normalized, Unicode-case-folded key that collapses whitespace and ignores
+    /// emoji while keeping punctuation significant.
     #[prost(string, tag = "2")]
     pub alias: ::prost::alloc::string::String,
 }

common/src/search.rs

@@ -120,7 +120,7 @@ pub fn canonical_search_number(input: &str) -> String {
 
 /// Normalizes a column name to the JSON-key form used at index time.
 pub fn normalize_column_name(column: &str) -> String {
-    column.to_ascii_lowercase()
+    crate::alias::canonical_alias(column)
 }
 
 /// Creates the column-aware search schema.

common/src/search_light.rs

@@ -65,7 +65,7 @@ pub fn canonical_search_number(input: &str) -> String {
 }
 
 pub fn normalize_column_name(column: &str) -> String {
-    column.to_ascii_lowercase()
+    crate::alias::canonical_alias(column)
 }
 
 #[cfg(test)]