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ProvSQL SQL API
Adding support for provenance and uncertainty management to PostgreSQL databases
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ProvSQL SQL API
Adding support for provenance and uncertainty management to PostgreSQL databases
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Installation-time advisory: if provsql is not in the database's default search_path, point the user at setup_search_path(). More...
Types | |
| TYPE | update_provenance |
| Table recording the history of INSERT, UPDATE, DELETE, and UNDO operations. More... | |
Functions | |
| UUID | transaction_token () |
| The update gate standing for the current transaction. | |
| trigger | stamp_commit_time () |
| Deferred trigger stamping a log row with its commit time. | |
| DO TRIGGER | insert_statement_trigger () |
| Trigger function for INSERT statement provenance tracking. | |
| TRIGGER | update_statement_trigger () |
| Trigger function for UPDATE statement provenance tracking. | |
Installation-time advisory: if provsql is not in the database's default search_path, point the user at setup_search_path().
reset_val reflects the configured session default (postgresql.conf / ALTER DATABASE / ALTER ROLE), unaffected by the SET search_path statements this script ran. CREATE EXTENSION raises client_min_messages to WARNING for the duration of the script, so we lower it around the RAISE NOTICE. SET LOCAL only: it unwinds by itself when CREATE EXTENSION's transaction ends. An explicit save/restore here would capture the WARNING clamp (already in force when this block runs) and restore that at session level, leaving the whole installing session with NOTICEs suppressed. Final constants-cache refresh. The planned SELECT statements earlier in this script (reset_constants_cache itself, the zero/one create_gate calls) make the installing session memoize the OID constants mid-script, while objects defined later (notably the choose aggregate, used by the scalar-subquery decorrelation) do not exist yet. Their optional lookups then stay InvalidOid for the rest of the session, silently disabling the corresponding rewrites (e.g. IN/NOT IN over a tracked relation would raise "Subqueries ... not supported") until a new connection. Refreshing here, after every object exists, repairs the installing session's cache.
Extended provenance tracking for INSERT, UPDATE, DELETE, and UNDO operations, including temporal validity ranges.
| DO TRIGGER insert_statement_trigger | ( | ) |
Trigger function for INSERT statement provenance tracking.
Records the insertion in update_provenance and multiplies provenance tokens of inserted rows with the insert token.
| trigger stamp_commit_time | ( | ) |
Deferred trigger stamping a log row with its commit time.
CURRENT_TIMESTAMP is the transaction's start time, so two overlapping transactions can commit in the opposite order of the validity they recorded. This fires at commit – it is a constraint trigger declared DEFERRABLE INITIALLY DEFERRED – and moves the row's TIMESTAMP and the lower bound of its validity to clock_timestamp(), which by then is the commit time to within the commit itself.
| UUID transaction_token | ( | ) |
The update gate standing for the current transaction.
Each data-modification statement already mints an update gate of its own, but nothing tied the statements of one transaction together: a reader of update_provenance could not tell that two rows came from the same transaction, and undo() could reverse a statement but not "the transaction". This mints one gate per transaction, on the first tracked modification, and hands the same one back for the rest of it.
Where a transaction's gate lives is SET LOCAL, so it vanishes when the transaction ends, whether it commits or rolls back – and a rolled-back transaction leaves no update_provenance row for it either, since that row is an ordinary heap insert.
| TRIGGER update_statement_trigger | ( | ) |
Trigger function for UPDATE statement provenance tracking.
Records the update in update_provenance. Multiplies new-row tokens with the update token and applies monus to old-row tokens.