/*
* refresh_by_match_merge
*
* Refresh a materialized view with transactional semantics, while allowing
* concurrent reads.
*
* This is called after a new version of the data has been created in a
* temporary table. It performs a full outer join against the old version of
* the data, producing "diff" results. This join cannot work if there are any
* duplicated rows in either the old or new versions, in the sense that every
* column would compare as equal between the two rows. It does work correctly
* in the face of rows which have at least one NULL value, with all non-NULL
* columns equal. The behavior of NULLs on equality tests and on UNIQUE
* indexes turns out to be quite convenient here; the tests we need to make
* are consistent with default behavior. If there is at least one UNIQUE
* index on the materialized view, we have exactly the guarantee we need.
*
* The temporary table used to hold the diff results contains just the TID of
* the old record (if matched) and the ROW from the new table as a single
* column of complex record type (if matched).
*
* Once we have the diff table, we perform set-based DELETE and INSERT
* operations against the materialized view, and discard both temporary
* tables.
*
* Everything from the generation of the new data to applying the differences
* takes place under cover of an ExclusiveLock, since it seems as though we
* would want to prohibit not only concurrent REFRESH operations, but also
* incremental maintenance. It also doesn't seem reasonable or safe to allow
* SELECT FOR UPDATE or SELECT FOR SHARE on rows being updated or deleted by
* this command.
*/
static void
refresh_by_match_merge(Oid matviewOid, Oid tempOid, Oid relowner,
int save_sec_context)
{
StringInfoData querybuf;
Relation matviewRel;
Relation tempRel;
char *matviewname;
char *tempname;
char *diffname;
TupleDesc tupdesc;
bool foundUniqueIndex;
List *indexoidlist;
ListCell *indexoidscan;
int16 relnatts;
bool *usedForQual;
initStringInfo(&querybuf);
matviewRel = heap_open(matviewOid, NoLock);
matviewname = quote_qualified_identifier(get_namespace_name(RelationGetNamespace(matviewRel)),
RelationGetRelationName(matviewRel));
tempRel = heap_open(tempOid, NoLock);
tempname = quote_qualified_identifier(get_namespace_name(RelationGetNamespace(tempRel)),
RelationGetRelationName(tempRel));
diffname = make_temptable_name_n(tempname, 2);
relnatts = matviewRel->rd_rel->relnatts;
usedForQual = (bool *) palloc0(sizeof(bool) * relnatts);
/* Open SPI context. */
if (SPI_connect() != SPI_OK_CONNECT)
elog(ERROR, "SPI_connect failed");
/* Analyze the temp table with the new contents. */
appendStringInfo(&querybuf, "ANALYZE %s", tempname);
if (SPI_exec(querybuf.data, 0) != SPI_OK_UTILITY)
elog(ERROR, "SPI_exec failed: %s", querybuf.data);
/*
* We need to ensure that there are not duplicate rows without NULLs in
* the new data set before we can count on the "diff" results. Check for
* that in a way that allows showing the first duplicated row found. Even
* after we pass this test, a unique index on the materialized view may
* find a duplicate key problem.
*/
resetStringInfo(&querybuf);
appendStringInfo(&querybuf,
"SELECT newdata FROM %s newdata "
"WHERE newdata IS NOT NULL AND EXISTS "
"(SELECT * FROM %s newdata2 WHERE newdata2 IS NOT NULL "
"AND newdata2 OPERATOR(pg_catalog.*=) newdata "
"AND newdata2.ctid OPERATOR(pg_catalog.<>) "
"newdata.ctid) LIMIT 1",
tempname, tempname);
if (SPI_execute(querybuf.data, false, 1) != SPI_OK_SELECT)
elog(ERROR, "SPI_exec failed: %s", querybuf.data);
if (SPI_processed > 0)
{
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
errmsg("new data for \"%s\" contains duplicate rows without any null columns",
RelationGetRelationName(matviewRel)),
errdetail("Row: %s",
SPI_getvalue(SPI_tuptable->vals[0], SPI_tuptable->tupdesc, 1))));
}
SetUserIdAndSecContext(relowner,
save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
/* Start building the query for creating the diff table. */
resetStringInfo(&querybuf);
appendStringInfo(&querybuf,
"CREATE TEMP TABLE %s AS "
"SELECT mv.ctid AS tid, newdata "
"FROM %s mv FULL JOIN %s newdata ON (",
diffname, matviewname, tempname);
/*
* Get the list of index OIDs for the table from the relcache, and look up
* each one in the pg_index syscache. We will test for equality on all
* columns present in all unique indexes which only reference columns and
* include all rows.
*/
tupdesc = matviewRel->rd_att;
foundUniqueIndex = false;
indexoidlist = RelationGetIndexList(matviewRel);
foreach(indexoidscan, indexoidlist)
{
Oid indexoid = lfirst_oid(indexoidscan);
Relation indexRel;
Form_pg_index indexStruct;
indexRel = index_open(indexoid, RowExclusiveLock);
indexStruct = indexRel->rd_index;
/*
* We're only interested if it is unique, valid, contains no
* expressions, and is not partial.
*/
if (indexStruct->indisunique &&
IndexIsValid(indexStruct) &&
RelationGetIndexExpressions(indexRel) == NIL &&
RelationGetIndexPredicate(indexRel) == NIL)
{
int numatts = indexStruct->indnatts;
int i;
/* Add quals for all columns from this index. */
for (i = 0; i < numatts; i++)
{
int attnum = indexStruct->indkey.values[i];
Oid type;
Oid op;
const char *colname;
/*
* Only include the column once regardless of how many times
* it shows up in how many indexes.
*/
if (usedForQual[attnum - 1])
continue;
usedForQual[attnum - 1] = true;
/*
* Actually add the qual, ANDed with any others.
*/
if (foundUniqueIndex)
appendStringInfoString(&querybuf, " AND ");
colname = quote_identifier(NameStr((tupdesc->attrs[attnum - 1])->attname));
appendStringInfo(&querybuf, "newdata.%s ", colname);
type = attnumTypeId(matviewRel, attnum);
op = lookup_type_cache(type, TYPECACHE_EQ_OPR)->eq_opr;
mv_GenerateOper(&querybuf, op);
appendStringInfo(&querybuf, " mv.%s", colname);
foundUniqueIndex = true;
}
}
/* Keep the locks, since we're about to run DML which needs them. */
index_close(indexRel, NoLock);
}
/*
* refresh_by_match_merge
*
* Refresh a materialized view with transactional semantics, while allowing
* concurrent reads.
*
* This is called after a new version of the data has been created in a
* temporary table. It performs a full outer join against the old version of
* the data, producing "diff" results. This join cannot work if there are any
* duplicated rows in either the old or new versions, in the sense that every
* column would compare as equal between the two rows. It does work correctly
* in the face of rows which have at least one NULL value, with all non-NULL
* columns equal. The behavior of NULLs on equality tests and on UNIQUE
* indexes turns out to be quite convenient here; the tests we need to make
* are consistent with default behavior. If there is at least one UNIQUE
* index on the materialized view, we have exactly the guarantee we need. By
* joining based on equality on all columns which are part of any unique
* index, we identify the rows on which we can use UPDATE without any problem.
* If any column is NULL in either the old or new version of a row (or both),
* we must use DELETE and INSERT, since there could be multiple rows which are
* NOT DISTINCT FROM each other, and we could otherwise end up with the wrong
* number of occurrences in the updated relation. The temporary table used to
* hold the diff results contains just the TID of the old record (if matched)
* and the ROW from the new table as a single column of complex record type
* (if matched).
*
* Once we have the diff table, we perform set-based DELETE, UPDATE, and
* INSERT operations against the materialized view, and discard both temporary
* tables.
*
* Everything from the generation of the new data to applying the differences
* takes place under cover of an ExclusiveLock, since it seems as though we
* would want to prohibit not only concurrent REFRESH operations, but also
* incremental maintenance. It also doesn't seem reasonable or safe to allow
* SELECT FOR UPDATE or SELECT FOR SHARE on rows being updated or deleted by
* this command.
*/
static void
refresh_by_match_merge(Oid matviewOid, Oid tempOid)
{
StringInfoData querybuf;
Relation matviewRel;
Relation tempRel;
char *matviewname;
char *tempname;
char *diffname;
TupleDesc tupdesc;
bool foundUniqueIndex;
List *indexoidlist;
ListCell *indexoidscan;
int16 relnatts;
bool *usedForQual;
Oid save_userid;
int save_sec_context;
int save_nestlevel;
initStringInfo(&querybuf);
matviewRel = heap_open(matviewOid, NoLock);
matviewname = quote_qualified_identifier(get_namespace_name(RelationGetNamespace(matviewRel)),
RelationGetRelationName(matviewRel));
tempRel = heap_open(tempOid, NoLock);
tempname = quote_qualified_identifier(get_namespace_name(RelationGetNamespace(tempRel)),
RelationGetRelationName(tempRel));
diffname = make_temptable_name_n(tempname, 2);
relnatts = matviewRel->rd_rel->relnatts;
usedForQual = (bool *) palloc0(sizeof(bool) * relnatts);
/* Open SPI context. */
if (SPI_connect() != SPI_OK_CONNECT)
elog(ERROR, "SPI_connect failed");
/* Analyze the temp table with the new contents. */
appendStringInfo(&querybuf, "ANALYZE %s", tempname);
if (SPI_exec(querybuf.data, 0) != SPI_OK_UTILITY)
elog(ERROR, "SPI_exec failed: %s", querybuf.data);
/*
* We need to ensure that there are not duplicate rows without NULLs in
* the new data set before we can count on the "diff" results. Check for
* that in a way that allows showing the first duplicated row found. Even
* after we pass this test, a unique index on the materialized view may
* find a duplicate key problem.
*/
resetStringInfo(&querybuf);
appendStringInfo(&querybuf,
"SELECT x FROM %s x WHERE x IS NOT NULL AND EXISTS "
"(SELECT * FROM %s y WHERE y IS NOT NULL "
"AND (y.*) = (x.*) AND y.ctid <> x.ctid) LIMIT 1",
tempname, tempname);
if (SPI_execute(querybuf.data, false, 1) != SPI_OK_SELECT)
elog(ERROR, "SPI_exec failed: %s", querybuf.data);
if (SPI_processed > 0)
{
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
errmsg("new data for \"%s\" contains duplicate rows without any NULL columns",
RelationGetRelationName(matviewRel)),
errdetail("Row: %s",
SPI_getvalue(SPI_tuptable->vals[0], SPI_tuptable->tupdesc, 1))));
}
/* Start building the query for creating the diff table. */
resetStringInfo(&querybuf);
appendStringInfo(&querybuf,
"CREATE TEMP TABLE %s AS "
"SELECT x.ctid AS tid, y FROM %s x FULL JOIN %s y ON (",
diffname, matviewname, tempname);
/*
* Get the list of index OIDs for the table from the relcache, and look up
* each one in the pg_index syscache. We will test for equality on all
* columns present in all unique indexes which only reference columns and
* include all rows.
*/
tupdesc = matviewRel->rd_att;
foundUniqueIndex = false;
indexoidlist = RelationGetIndexList(matviewRel);
foreach(indexoidscan, indexoidlist)
{
Oid indexoid = lfirst_oid(indexoidscan);
HeapTuple indexTuple;
Form_pg_index index;
indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
if (!HeapTupleIsValid(indexTuple)) /* should not happen */
elog(ERROR, "cache lookup failed for index %u", indexoid);
index = (Form_pg_index) GETSTRUCT(indexTuple);
/* We're only interested if it is unique and valid. */
if (index->indisunique && IndexIsValid(index))
{
int numatts = index->indnatts;
int i;
bool expr = false;
Relation indexRel;
/* Skip any index on an expression. */
for (i = 0; i < numatts; i++)
{
if (index->indkey.values[i] == 0)
{
expr = true;
break;
}
}
if (expr)
{
ReleaseSysCache(indexTuple);
continue;
}
/* Skip partial indexes. */
indexRel = index_open(index->indexrelid, RowExclusiveLock);
if (RelationGetIndexPredicate(indexRel) != NIL)
{
index_close(indexRel, NoLock);
ReleaseSysCache(indexTuple);
continue;
}
/* Hold the locks, since we're about to run DML which needs them. */
index_close(indexRel, NoLock);
/* Add quals for all columns from this index. */
for (i = 0; i < numatts; i++)
{
int attnum = index->indkey.values[i];
Oid type;
Oid op;
const char *colname;
/*
* Only include the column once regardless of how many times
* it shows up in how many indexes.
*
* This is also useful later to omit columns which can not
* have changed from the SET clause of the UPDATE statement.
*/
if (usedForQual[attnum - 1])
continue;
usedForQual[attnum - 1] = true;
/*
* Actually add the qual, ANDed with any others.
*/
if (foundUniqueIndex)
appendStringInfoString(&querybuf, " AND ");
colname = quote_identifier(NameStr((tupdesc->attrs[attnum - 1])->attname));
appendStringInfo(&querybuf, "y.%s ", colname);
type = attnumTypeId(matviewRel, attnum);
op = lookup_type_cache(type, TYPECACHE_EQ_OPR)->eq_opr;
mv_GenerateOper(&querybuf, op);
appendStringInfo(&querybuf, " x.%s", colname);
foundUniqueIndex = true;
}
}
ReleaseSysCache(indexTuple);
}
