Add bm25 aux table invariant tests

lantern_extras/src/bm25_agg.rs

@@ -582,13 +582,6 @@ mod tests {
     use itertools::Itertools;
     use pgrx::prelude::*;
 
-    // TODO: turn this into a test:
-    // select term, cardinality(array_agg(DISTINCT term_freq)) as uniq_term_freq_must_be_1,
-    // (array_agg(DISTINCT term_freq))[1] any_term_freq_must_be_equal_to_next_col ,
-    // SUM(cardinality(doc_ids))  from corpus_bm25 where term_freq != cardinality(doc_ids)
-    // GROUP BY term ORDER BY term;
-    // TODO: check that doc_ids contain UNIQUE doc ids
-
     #[pg_test]
     fn test_bm25_agg_and_api() -> spi::Result<()> {
         // Step 1: Create the documents table
@@ -711,6 +704,37 @@ mod tests {
         // the added row had one new word, so the bm25 table must grow by 1
         assert_eq!(new_len, prev_len + 1);
 
+        // Test some axuilary _bm25 table invariants
+
+        let doc_ids_invariant = Spi::get_one::<bool>(
+            "SELECT NOT EXISTS (SELECT 1 FROM documents_bm25 WHERE NOT cardinality(doc_ids) = cardinality((SELECT array_agg(DISTINCT e) FROM unnest( doc_ids) e)))",
+        )?;
+        assert!(
+            doc_ids_invariant.unwrap(),
+            "doc_ids must contain unique doc ids"
+        );
+
+        // Test for term frequency invariants
+        let term_freq_invariant = Spi::get_one::<bool>(
+            "SELECT NOT EXISTS (
+                SELECT 1
+                FROM (
+                    SELECT term, cardinality(array_agg(DISTINCT term_freq)) AS uniq_term_freq_must_be_1,
+                           (array_agg(DISTINCT term_freq))[1] AS any_term_freq_must_be_equal_to_next_col,
+                           SUM(cardinality(doc_ids))
+                    FROM documents_bm25
+                    WHERE term_freq != cardinality(doc_ids)
+                    GROUP BY term
+                ) AS subquery
+                WHERE uniq_term_freq_must_be_1 != 1
+            );",
+        )?;
+
+        // note: this invariant needs to be modified once insertions become allowed
+        assert!(
+            term_freq_invariant.unwrap(),
+            "Each term must have a unique term frequency equal to the cardinality of doc_ids"
+        );
         // Test the bm25_score function
         // The bm25_score function calculates the BM25 score for the given query in the given
         // document