duckdb index columns

plugins/dbgate-plugin-duckdb/src/backend/extractIndexColumns.js

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+// this algoruthm is implemented by ChatGPT o3
+
+function sliceColumnList(ddl) {
+  // ① jump to the first “(” that follows the ON <table> qualifier
+  const onMatch = /ON\s+(?:"[^"]+"|\w+)(?:\s*\.\s*(?:"[^"]+"|\w+))*\s*\(/i.exec(ddl);
+  if (!onMatch) return '';
+  const start = onMatch.index + onMatch[0].length - 1; // points at the "("
+
+  // ② walk forward until depth returns to 0
+  let depth = 0,
+    i = start,
+    end = -1;
+  while (i < ddl.length) {
+    const ch = ddl[i++];
+    if (ch === '(') depth++;
+    else if (ch === ')') {
+      depth--;
+      if (depth === 0) {
+        end = i - 1;
+        break;
+      }
+    }
+  }
+  return end === -1 ? '' : ddl.slice(start + 1, end); // inside the ()
+}
+
+function splitTopLevel(list) {
+  const parts = [];
+  let depth = 0,
+    last = 0;
+  for (let i = 0; i <= list.length; i++) {
+    const ch = list[i] ?? ','; // virtual comma at the end
+    if (ch === '(') depth++;
+    else if (ch === ')') depth--;
+    if (ch === ',' && depth === 0) {
+      parts.push(list.slice(last, i).trim());
+      last = i + 1;
+    }
+  }
+  return parts.filter(Boolean);
+}
+
+function clean(segment) {
+  return (
+    segment
+      // drop ASC|DESC, NULLS FIRST|LAST
+      .replace(/\bASC\b|\bDESC\b|\bNULLS\s+(FIRST|LAST)\b/gi, '')
+      // un-wrap one-liner functions:  LOWER(col) -> col
+      .replace(/^[A-Za-z_][\w$]*\(\s*([^()]+?)\s*\)$/i, '$1')
+      // chop any schema- or table- prefix:  tbl.col -> col
+      .replace(/^.*\.(?=[^.)]+$)/, '')
+      // strip double-quotes
+      .replace(/"/g, '')
+      .trim()
+  );
+}
+
+function extractIndexColumns(sql) {
+  const sqlText = sql // your variable
+    .replace(/\s+/g, ' ') // collapse whitespace
+    .replace(/--.*?$/gm, '') // strip line comments
+    .trim();
+
+  const list = sliceColumnList(sqlText);
+  if (!list) return [];
+  return splitTopLevel(list).map(clean);
+}
+
+module.exports = extractIndexColumns;