test(gin): add before/after test for GIN index usage

Verify that containment queries use Seq Scan before index creation
and switch to using the GIN index after creation. Exports explain_query
and assert_uses_seq_scan helpers to support this test pattern.

Author: tobyhede

tests/sqlx/src/lib.rs

@@ -11,9 +11,9 @@ pub mod selectors;
 
 pub use assertions::QueryAssertion;
 pub use helpers::{
-    analyze_table, assert_uses_index, create_jsonb_gin_index, get_encrypted_term,
-    get_ore_encrypted, get_ore_encrypted_as_jsonb, get_ste_vec_encrypted,
-    get_ste_vec_selector_term, get_ste_vec_term_by_id,
+    analyze_table, assert_uses_index, assert_uses_seq_scan, create_jsonb_gin_index,
+    explain_query, get_encrypted_term, get_ore_encrypted, get_ore_encrypted_as_jsonb,
+    get_ste_vec_encrypted, get_ste_vec_selector_term, get_ste_vec_term_by_id,
 };
 pub use index_types as IndexTypes;
 pub use selectors::Selectors;

tests/sqlx/tests/containment_with_index_tests.rs

@@ -9,7 +9,10 @@
 //! Uses the ste_vec_vast table (500 rows) from migration 005_install_ste_vec_vast_data.sql
 
 use anyhow::Result;
-use eql_tests::{analyze_table, assert_uses_index, create_jsonb_gin_index, get_ste_vec_encrypted};
+use eql_tests::{
+    analyze_table, assert_uses_index, assert_uses_seq_scan, create_jsonb_gin_index,
+    explain_query, get_ste_vec_encrypted,
+};
 use sqlx::PgPool;
 
 // Constants for ste_vec_vast table testing
@@ -181,3 +184,38 @@ async fn jsonb_array_count_with_index(pool: PgPool) -> Result<()> {
 
     Ok(())
 }
+
+
+#[sqlx::test]
+async fn jsonb_containment_uses_seq_scan_without_index(pool: PgPool) -> Result<()> {
+    // Test: Verify sequential scan is used BEFORE GIN index is created
+    //
+    // This test demonstrates that the GIN index actually makes a difference:
+    // 1. Without index: query uses Seq Scan
+    // 2. After creating index: query uses Index Scan
+    //
+    // This is a "before and after" test to prove the index improves query execution.
+
+    // Run ANALYZE first to ensure planner has accurate statistics
+    analyze_table(&pool, STE_VEC_VAST_TABLE).await?;
+
+    let id = 1;
+    let row = get_ste_vec_encrypted(&pool, STE_VEC_VAST_TABLE, id).await?;
+
+    let sql = format!(
+        "SELECT 1 FROM {} WHERE eql_v2.jsonb_array(e) @> eql_v2.jsonb_array('{}'::eql_v2_encrypted) LIMIT 1",
+        STE_VEC_VAST_TABLE, row
+    );
+
+    // BEFORE: Without index, should use Seq Scan
+    let explain_before = explain_query(&pool, &sql).await?;
+    assert_uses_seq_scan(&explain_before);
+
+    // Create the GIN index
+    setup_ste_vec_vast_gin_index(&pool).await?;
+
+    // AFTER: With index, should use the GIN index
+    assert_uses_index(&pool, &sql, STE_VEC_VAST_GIN_INDEX).await?;
+
+    Ok(())
+}