Consider tuple duplicity in maintenance of EXISTS views

When a tuple is inserted into a table in an EXISTS subquery,
the duplicity of row is computed by count(*), but it was not
considered and only one tuple was inserted with ignoring
the duplicity.

This is fixed by duplicating rows as much as the duplicity
by using generate_series at inserting.

(Issue #82)

expected/pg_ivm.out

@@ -828,6 +828,19 @@ SELECT * FROM mv_ivm_exists_subquery2 ORDER BY i, j;
  4 |  40 |                      1
 (4 rows)
 
+DELETE FROM mv_base_b WHERE i = 1 or i = 3;
+INSERT INTO mv_base_b VALUES (1,100), (3,300);
+SELECT * FROM mv_ivm_exists_subquery ORDER BY i, j;
+ i |  j  | __ivm_exists_count_0__ 
+---+-----+------------------------
+ 1 |  10 |                      1
+ 1 |  10 |                      1
+ 3 |  30 |                      1
+ 3 |  30 |                      1
+ 3 | 300 |                      1
+ 4 |  40 |                      1
+(6 rows)
+
 ROLLBACK;
 -- support simple subquery in FROM clause
 BEGIN;

matview.c

@@ -2523,6 +2523,7 @@ apply_new_delta_with_count(const char *matviewname, const char* deltaname_new,
 	StringInfoData	returning_keys;
 	ListCell	*lc;
 	char	*match_cond = "";
+	StringInfoData	deltaname_new_for_insert;
 
 	/* build WHERE condition for searching tuples to be updated */
 	match_cond = get_matching_condition_string(keys);
@@ -2543,6 +2544,24 @@ apply_new_delta_with_count(const char *matviewname, const char* deltaname_new,
 	else
 		appendStringInfo(&returning_keys, "NULL");
 
+	/*
+	 * If count_colname is not "__ivm_count__", the view contains EXISTS
+	 * subquery and the count column to be updated here is "__ivm_exists_count_*"
+	 * that stores the number of columns generated by corresponding EXISTS
+	 * subquery for each row in the view. In this case, __ivm_count__ in
+	 * deltaname_new stores duplicity of rows, and each row need to be
+	 * duplicated as much as __ivm_count__ by using generate_series at
+	 * inserting.
+	 */
+	initStringInfo(&deltaname_new_for_insert);
+	if (!strcmp(count_colname, "__ivm_count__"))
+		appendStringInfo(&deltaname_new_for_insert, "%s", deltaname_new);
+	else
+		appendStringInfo(&deltaname_new_for_insert,
+			"(SELECT diff.* FROM %s diff,"
+				"pg_catalog.generate_series(1, diff.\"__ivm_count__\"))",
+			deltaname_new);
+
 	/* Search for matching tuples from the view and update if found or insert if not. */
 	initStringInfo(&querybuf);
 	appendStringInfo(&querybuf,
@@ -2561,9 +2580,8 @@ apply_new_delta_with_count(const char *matviewname, const char* deltaname_new,
 					match_cond,
 					returning_keys.data,
 					matviewname, target_list->data,
-					target_list->data, deltaname_new,
+					target_list->data, deltaname_new_for_insert.data,
 					match_cond);
-
 	if (SPI_exec(querybuf.data, 0) != SPI_OK_INSERT)
 		elog(ERROR, "SPI_exec failed: %s", querybuf.data);
 }

sql/pg_ivm.sql

@@ -269,6 +269,9 @@ DELETE FROM mv_base_a WHERE (i,j) = (1,60);
 DELETE FROM mv_base_b WHERE i = 2;
 SELECT * FROM mv_ivm_exists_subquery ORDER BY i, j;
 SELECT * FROM mv_ivm_exists_subquery2 ORDER BY i, j;
+DELETE FROM mv_base_b WHERE i = 1 or i = 3;
+INSERT INTO mv_base_b VALUES (1,100), (3,300);
+SELECT * FROM mv_ivm_exists_subquery ORDER BY i, j;
 ROLLBACK;
 
 -- support simple subquery in FROM clause