f1166c0421
Previously, the view contents could become inconsistent with the base tables in the following scenarios: 1) A concurrent transaction modifies a base table and commits before the incremental view maintenance starts in the current transaction. 2) A concurrent transaction modifies a base table and commits before the create_immv or refresh_immv command generates data. 3) Concurrent transactions incrementally update a view with a self-join or modify multiple base tables simultaneously. Incremental updates of a view are generally performed sequentially using an exclusive lock. However, even if we are able to acquire the lock, a concurrent transaction may have already incrementally updated the view and been committed before we can acquire it. In REPEATABLE READ or SERIALIZABLE isolation levels, this could lead to an inconsistent view state, which is the cause of the first issue. To fix this, a new field, lastivmupdate, has been added to the pg_ivm_immv catalog to record the transaction ID of the most recent update to the view. Before performing view maintenance, the transaction ID is checked. If the transaction was still in progress at the start of the current transaction, an error is raised to prevent anomalies. To fix the second issue, the timing of CreateTrigger() has been moved to before data generation. This ensures that locks conflicting with table modifications have been acquired on all base tables. In addition, the latest snapshot is used in READ COMMITTED level during the data generation to reflect committed changes from concurrent transactions. Additionally, inconsistencies that cannot be avoided through locking are prevented by checking the transaction ID of the last view update, as done for the first issue. However, concurrent table modifications and create_immv execution still cannot be detected at the time of view creation. Therefore, create_immv raises a warning in REPEATABLE READ or SERIALIZABLE isolation levels, suggesting that the command be used in READ COMMITTED mode or that refresh_immv be executed afterward to ensure the view remains consistent. The third issue was caused by the snapshot used for checking tuple visibility in the table's pre-update state not being the latest one. To fix this, the latest snapshot is now used in READ COMMITTED mode. Isolation tests are also added. Issue #104
71 lines
2.4 KiB
C
71 lines
2.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_ivm.h
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* incremental view maintenance extension
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*
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* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
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* Portions Copyright (c) 2022, IVM Development Group
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef _PG_IVM_H_
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#define _PG_IVM_H_
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#include "catalog/objectaddress.h"
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#include "fmgr.h"
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#include "nodes/params.h"
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#include "nodes/pathnodes.h"
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#include "parser/parse_node.h"
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#include "tcop/dest.h"
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#include "utils/queryenvironment.h"
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#define Natts_pg_ivm_immv 4
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#define Anum_pg_ivm_immv_immvrelid 1
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#define Anum_pg_ivm_immv_viewdef 2
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#define Anum_pg_ivm_immv_ispopulated 3
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#define Anum_pg_ivm_immv_lastivmupdate 4
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/* pg_ivm.c */
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extern void CreateChangePreventTrigger(Oid matviewOid);
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extern Oid PgIvmImmvRelationId(void);
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extern Oid PgIvmImmvPrimaryKeyIndexId(void);
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extern bool isImmv(Oid immv_oid);
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extern List *PgIvmFuncName(char *name);
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/* createas.c */
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extern ObjectAddress ExecCreateImmv(ParseState *pstate, CreateTableAsStmt *stmt,
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QueryCompletion *qc);
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extern void CreateIvmTriggersOnBaseTables(Query *qry, Oid matviewOid);
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extern void CreateIndexOnIMMV(Query *query, Relation matviewRel);
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extern Query *rewriteQueryForIMMV(Query *query, List *colNames);
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extern void makeIvmAggColumn(ParseState *pstate, Aggref *aggref, char *resname, AttrNumber *next_resno, List **aggs);
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/* matview.c */
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extern Query *get_immv_query(Relation matviewRel);
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extern ObjectAddress ExecRefreshImmv(const RangeVar *relation, bool skipData,
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const char *queryString, QueryCompletion *qc);
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extern ObjectAddress RefreshImmvByOid(Oid matviewOid, bool is_create, bool skipData,
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const char *queryString, QueryCompletion *qc);
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extern bool ImmvIncrementalMaintenanceIsEnabled(void);
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extern Datum IVM_immediate_before(PG_FUNCTION_ARGS);
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extern Datum IVM_immediate_maintenance(PG_FUNCTION_ARGS);
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extern Query* rewrite_query_for_exists_subquery(Query *query);
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extern Datum ivm_visible_in_prestate(PG_FUNCTION_ARGS);
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extern void AtAbort_IVM(SubTransactionId subtxid);
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extern void AtPreCommit_IVM(void);
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extern char *getColumnNameStartWith(RangeTblEntry *rte, char *str, int *attnum);
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extern bool isIvmName(const char *s);
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/* ruleutils.c */
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extern char *pg_ivm_get_viewdef(Relation immvrel, bool pretty);
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/* subselect.c */
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extern void inline_cte(PlannerInfo *root, CommonTableExpr *cte);
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#endif
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