[Tarantool-patches] [PATCH] sql: fix off-by-one error in QP

[Nikita Pettik <korablev@tarantool.org>]

In scope of 8fac697 it was fixed misbehavior while passing floating
point values to integer iterator. Unfortunately, that patch introduced
off-by-one error. Number of constraints (equalities and inequalities)
can not be greater than number of key parts (obviously, each constraint
can be tested against at most one index part). Inequality constraint can
involve only field representing last key part. To get it number of
constraints was used as index. However, since array is 0-based, the last
key part should be calculated as parts[eq_numb - 1]. Before this patch
it was parts[eq_numb].

Closes #4558
---
Branch: https://github.com/tarantool/tarantool/commits/np/gh-4558-off-by-one-qp-fix
Issue: https://github.com/tarantool/tarantool/issues/4558

 src/box/sql/wherecode.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/box/sql/wherecode.c b/src/box/sql/wherecode.c
index de51c0ba5..5bc27f134 100644
--- a/src/box/sql/wherecode.c
+++ b/src/box/sql/wherecode.c
@@ -1118,10 +1118,20 @@ sqlWhereCodeOneLoopStart(WhereInfo * pWInfo,	/* Complete information about the W
 			}
 		}
 		/* Inequality constraint comes always at the end of list. */
-		enum field_type ineq_type = idx_def->key_def->parts[nEq].type;
-		if (pRangeStart != NULL && (ineq_type == FIELD_TYPE_INTEGER ||
-					    ineq_type == FIELD_TYPE_UNSIGNED))
-			force_integer_reg = regBase + nEq;
+		part_count = idx_def->key_def->part_count;
+		if (pRangeStart != NULL) {
+			/*
+			 * nEq == 0 means that filter condition
+			 * contains only inequality.
+			 */
+			uint32_t ineq_idx = nEq == 0 ? 0 : nEq - 1;
+			assert(ineq_idx < part_count);
+			enum field_type ineq_type =
+				idx_def->key_def->parts[ineq_idx].type;
+			if (ineq_type == FIELD_TYPE_INTEGER ||
+			    ineq_type == FIELD_TYPE_UNSIGNED)
+				force_integer_reg = regBase + nEq;
+		}
 		emit_apply_type(pParse, regBase, nConstraint - bSeekPastNull,
 				start_types);
 		if (pLoop->nSkip > 0 && nConstraint == pLoop->nSkip) {
-- 
2.15.1