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fix(cypher): apply distinct before return limits #906

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fix(cypher): apply distinct before return limits #906

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6 changes: 3 additions & 3 deletions src/cypher/cypher.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4105,7 +4105,7 @@ static void build_return_columns(result_builder_t *rb, cbm_return_clause_t *ret)
static void execute_return_simple(cbm_return_clause_t *ret, binding_t *bindings, int bind_count,
int max_rows, result_builder_t *rb) {
int proj_cap = max_rows;
if (ret->limit > 0 && !ret->order_by && ret->skip <= 0) {
if (ret->limit > 0 && !ret->distinct && !ret->order_by && ret->skip <= 0) {
proj_cap = ret->limit;
}
for (int bi = 0; bi < bind_count && rb->row_count < proj_cap; bi++) {
Expand Down Expand Up @@ -4387,11 +4387,11 @@ static void execute_return_clause(cbm_query_t *q, cbm_return_clause_t *ret, bind
}
}

rb_apply_order_by(rb, ret);
rb_apply_skip_limit(rb, ret->skip, ret->limit >= 0 ? ret->limit : max_rows);
if (ret->distinct) {
rb_apply_distinct(rb);
}
rb_apply_order_by(rb, ret);
rb_apply_skip_limit(rb, ret->skip, ret->limit >= 0 ? ret->limit : max_rows);
}

static int execute_single(cbm_store_t *store, cbm_query_t *q, const char *project, int max_rows,
Expand Down
49 changes: 49 additions & 0 deletions tests/test_cypher.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2524,6 +2524,52 @@ TEST(cypher_issue237_distinct_order_limit) {
PASS();
}

/* #873: duplicate projected rows must be deduped before ORDER BY + LIMIT */
TEST(cypher_issue873_distinct_order_limit_dedupes_before_limit) {
cbm_store_t *s = setup_cypher_store();
cbm_cypher_result_t r = {0};
int rc = cbm_cypher_execute(
s, "MATCH (n) RETURN DISTINCT n.label AS label ORDER BY label LIMIT 2", "test", 0, &r);
ASSERT_EQ(rc, 0);
ASSERT_NULL(r.error);
ASSERT_EQ(r.row_count, 2);
ASSERT_STR_EQ(r.rows[0][0], "Function");
ASSERT_STR_EQ(r.rows[1][0], "Module");
cbm_cypher_result_free(&r);
cbm_store_close(s);
PASS();
}

/* #873: early LIMIT must not truncate rows before DISTINCT for simple RETURN */
TEST(cypher_issue873_distinct_limit_dedupes_before_limit) {
cbm_store_t *s = setup_cypher_store();
cbm_cypher_result_t r = {0};
int rc = cbm_cypher_execute(
s, "MATCH (n) RETURN DISTINCT n.label AS label LIMIT 2", "test", 0, &r);
ASSERT_EQ(rc, 0);
ASSERT_NULL(r.error);
ASSERT_EQ(r.row_count, 2);
cbm_cypher_result_free(&r);
cbm_store_close(s);
PASS();
}

/* #873: SKIP is applied after DISTINCT and ORDER BY, not before dedupe */
TEST(cypher_issue873_distinct_order_skip_limit_dedupes_before_skip) {
cbm_store_t *s = setup_cypher_store();
cbm_cypher_result_t r = {0};
int rc = cbm_cypher_execute(
s, "MATCH (n) RETURN DISTINCT n.label AS label ORDER BY label SKIP 1 LIMIT 1", "test",
0, &r);
ASSERT_EQ(rc, 0);
ASSERT_NULL(r.error);
ASSERT_EQ(r.row_count, 1);
ASSERT_STR_EQ(r.rows[0][0], "Module");
cbm_cypher_result_free(&r);
cbm_store_close(s);
PASS();
}

/* #252: toInteger() */
TEST(cypher_issue252_tointeger) {
cbm_store_t *s = setup_cypher_store();
Expand Down Expand Up @@ -2624,6 +2670,9 @@ SUITE(cypher) {
RUN_TEST(cypher_exec_match_all_functions);
RUN_TEST(cypher_issue240_labels_function);
RUN_TEST(cypher_issue237_distinct_order_limit);
RUN_TEST(cypher_issue873_distinct_order_limit_dedupes_before_limit);
RUN_TEST(cypher_issue873_distinct_limit_dedupes_before_limit);
RUN_TEST(cypher_issue873_distinct_order_skip_limit_dedupes_before_skip);
RUN_TEST(cypher_issue252_tointeger);
RUN_TEST(cypher_issue305_count_star_alias);
RUN_TEST(cypher_exec_where_eq);
Expand Down
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