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Allow TRUNCATE on base tables (#144)

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When a base table is truncated, the view content will be empty if the
view definition query does not contain an aggregate without a GROUP clause.
Therefore, such views can be truncated.

Aggregate views without a GROUP clause always have one row. Therefore,
if a base table is truncated, the view will not be empty and will contain
a row with NULL value (or 0 for count()). So, in this case, we refresh the
view instead of truncating it.
This commit is contained in:
Yugo Nagata 2022-06-21 21:25:22 +09:00
parent 57c8bac1a0
commit d99aeb848e
4 changed files with 161 additions and 3 deletions
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5
createas.c
View file

@ -509,9 +509,11 @@ CreateIvmTriggersOnBaseTablesRecurse(Query *qry, Node *node, Oid matviewOid,
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_INSERT, TRIGGER_TYPE_BEFORE, ex_lock);
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_DELETE, TRIGGER_TYPE_BEFORE, ex_lock);
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_UPDATE, TRIGGER_TYPE_BEFORE, ex_lock);
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_TRUNCATE, TRIGGER_TYPE_BEFORE, true);
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_INSERT, TRIGGER_TYPE_AFTER, ex_lock);
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_DELETE, TRIGGER_TYPE_AFTER, ex_lock);
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_UPDATE, TRIGGER_TYPE_AFTER, ex_lock);
CreateIvmTrigger(rte->relid, matviewOid, TRIGGER_TYPE_TRUNCATE, TRIGGER_TYPE_AFTER, true);
*relids = bms_add_member(*relids, rte->relid);
}
@ -577,6 +579,9 @@ CreateIvmTrigger(Oid relOid, Oid viewOid, int16 type, int16 timing, bool ex_lock
case TRIGGER_TYPE_UPDATE:
ivm_trigger->trigname = (timing == TRIGGER_TYPE_BEFORE ? "IVM_trigger_upd_before" : "IVM_trigger_upd_after");
break;
case TRIGGER_TYPE_TRUNCATE:
ivm_trigger->trigname = (timing == TRIGGER_TYPE_BEFORE ? "IVM_trigger_truncate_before" : "IVM_trigger_truncate_after");
break;
default:
elog(ERROR, "unsupported trigger type");
}

63
expected/pg_ivm.out
View file

@ -77,6 +77,23 @@ SELECT * FROM mv_ivm_1 ORDER BY 1,2,3;
4 | 40 | 104
(4 rows)
-- TRUNCATE a base table in join views
BEGIN;
TRUNCATE mv_base_a;
SELECT * FROM mv_ivm_1;
i | j | k
---+---+---
(0 rows)
ROLLBACK;
BEGIN;
TRUNCATE mv_base_b;
SELECT * FROM mv_ivm_1;
i | j | k
---+---+---
(0 rows)
ROLLBACK;
-- some query syntax
BEGIN;
CREATE FUNCTION ivm_func() RETURNS int LANGUAGE 'sql'
@ -245,6 +262,27 @@ SELECT * FROM mv_ivm_agg ORDER BY 1,2,3;
5 | 50 | 1 | 1 | 1
(5 rows)
ROLLBACK;
-- TRUNCATE a base table in aggregate views
BEGIN;
SELECT create_immv('mv_ivm_agg', 'SELECT i, SUM(j), COUNT(*) FROM mv_base_a GROUP BY i');
NOTICE: created index "mv_ivm_agg_index" on immv "mv_ivm_agg"
create_immv
-------------
5
(1 row)
TRUNCATE mv_base_a;
SELECT sum, count FROM mv_ivm_agg;
sum | count
-----+-------
(0 rows)
SELECT i, SUM(j), COUNT(*) FROM mv_base_a GROUP BY i;
i | sum | count
---+-----+-------
(0 rows)
ROLLBACK;
-- support aggregate functions without GROUP clause
BEGIN;
@ -277,6 +315,31 @@ SELECT * FROM mv_ivm_group ORDER BY 1;
| 0 | | 0 | 0 | | 0
(1 row)
ROLLBACK;
-- TRUNCATE a base table in aggregate views without GROUP clause
BEGIN;
SELECT create_immv('mv_ivm_group', 'SELECT SUM(j), COUNT(j), AVG(j) FROM mv_base_a');
NOTICE: could not create an index on immv "mv_ivm_group" automatically
DETAIL: This target list does not have all the primary key columns, or this view does not contain GROUP BY or DISTINCT clause.
HINT: Create an index on the immv for efficient incremental maintenance.
create_immv
-------------
1
(1 row)
TRUNCATE mv_base_a;
SELECT sum, count, avg FROM mv_ivm_group;
sum | count | avg
-----+-------+-----
| 0 |
(1 row)
SELECT SUM(j), COUNT(j), AVG(j) FROM mv_base_a;
sum | count | avg
-----+-------+-----
| 0 |
(1 row)
ROLLBACK;
-- resolved issue: When use AVG() function and values is indivisible, result of AVG() is incorrect.
BEGIN;

69
matview.c
View file

@ -816,9 +816,6 @@ IVM_immediate_maintenance(PG_FUNCTION_ARGS)
matviewRel = table_open(matviewOid, NoLock);
/* get view query*/
query = get_immv_query(matviewRel);
/* Make sure IMMV is a table. */
Assert(matviewRel->rd_rel->relkind == RELKIND_RELATION);
@ -848,6 +845,72 @@ IVM_immediate_maintenance(PG_FUNCTION_ARGS)
save_sec_context | SECURITY_RESTRICTED_OPERATION);
save_nestlevel = NewGUCNestLevel();
/* get view query*/
query = get_immv_query(matviewRel);
/*
* When a base table is truncated, the view content will be empty if the
* view definition query does not contain an aggregate without a GROUP clause.
* Therefore, such views can be truncated.
*
* Aggregate views without a GROUP clause always have one row. Therefore,
* if a base table is truncated, the view will not be empty and will contain
* a row with NULL value (or 0 for count()). So, in this case, we refresh the
* view instead of truncating it.
*/
if (TRIGGER_FIRED_BY_TRUNCATE(trigdata->tg_event))
{
if (!(query->hasAggs && query->groupClause == NIL))
{
OpenImmvIncrementalMaintenance();
ExecuteTruncateGuts(list_make1(matviewRel), list_make1_oid(matviewOid),
NIL, DROP_RESTRICT, false);
CloseImmvIncrementalMaintenance();
}
else
{
Oid OIDNewHeap;
DestReceiver *dest;
uint64 processed = 0;
Query *dataQuery = rewriteQueryForIMMV(query, NIL);
char relpersistence = matviewRel->rd_rel->relpersistence;
/*
* Create the transient table that will receive the regenerated data. Lock
* it against access by any other process until commit (by which time it
* will be gone).
*/
OIDNewHeap = make_new_heap(matviewOid, matviewRel->rd_rel->reltablespace,
relpersistence, ExclusiveLock);
LockRelationOid(OIDNewHeap, AccessExclusiveLock);
dest = CreateTransientRelDestReceiver(OIDNewHeap);
/* Generate the data */
processed = refresh_immv_datafill(dest, dataQuery, NULL, NULL, "");
refresh_by_heap_swap(matviewOid, OIDNewHeap, relpersistence);
/* Inform cumulative stats system about our activity */
pgstat_count_truncate(matviewRel);
pgstat_count_heap_insert(matviewRel, processed);
}
/* Clean up hash entry and delete tuplestores */
clean_up_IVM_hash_entry(entry);
/* Pop the original snapshot. */
PopActiveSnapshot();
table_close(matviewRel, NoLock);
/* Roll back any GUC changes */
AtEOXact_GUC(false, save_nestlevel);
/* Restore userid and security context */
SetUserIdAndSecContext(save_userid, save_sec_context);
return PointerGetDatum(NULL);
}
/*
* rewrite query for calculating deltas
*/

27
sql/pg_ivm.sql
View file

@ -31,6 +31,17 @@ SELECT * FROM mv_ivm_1 ORDER BY 1,2,3;
ROLLBACK;
SELECT * FROM mv_ivm_1 ORDER BY 1,2,3;
-- TRUNCATE a base table in join views
BEGIN;
TRUNCATE mv_base_a;
SELECT * FROM mv_ivm_1;
ROLLBACK;
BEGIN;
TRUNCATE mv_base_b;
SELECT * FROM mv_ivm_1;
ROLLBACK;
-- some query syntax
BEGIN;
CREATE FUNCTION ivm_func() RETURNS int LANGUAGE 'sql'
@ -71,6 +82,14 @@ INSERT INTO mv_base_a VALUES(2,100);
SELECT * FROM mv_ivm_agg ORDER BY 1,2,3;
ROLLBACK;
-- TRUNCATE a base table in aggregate views
BEGIN;
SELECT create_immv('mv_ivm_agg', 'SELECT i, SUM(j), COUNT(*) FROM mv_base_a GROUP BY i');
TRUNCATE mv_base_a;
SELECT sum, count FROM mv_ivm_agg;
SELECT i, SUM(j), COUNT(*) FROM mv_base_a GROUP BY i;
ROLLBACK;
-- support aggregate functions without GROUP clause
BEGIN;
SELECT create_immv('mv_ivm_group', 'SELECT SUM(j), COUNT(j), AVG(j) FROM mv_base_a');
@ -81,6 +100,14 @@ DELETE FROM mv_base_a;
SELECT * FROM mv_ivm_group ORDER BY 1;
ROLLBACK;
-- TRUNCATE a base table in aggregate views without GROUP clause
BEGIN;
SELECT create_immv('mv_ivm_group', 'SELECT SUM(j), COUNT(j), AVG(j) FROM mv_base_a');
TRUNCATE mv_base_a;
SELECT sum, count, avg FROM mv_ivm_group;
SELECT SUM(j), COUNT(j), AVG(j) FROM mv_base_a;
ROLLBACK;
-- resolved issue: When use AVG() function and values is indivisible, result of AVG() is incorrect.
BEGIN;
SELECT create_immv('mv_ivm_avg_bug', 'SELECT i, SUM(j), COUNT(j), AVG(j) FROM mv_base_A GROUP BY i');