Adding upstream version 16.2.upstream/16.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 114 insertions, 0 deletions

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+'\" t
+.\"     Title: SET CONSTRAINTS
+.\"    Author: The PostgreSQL Global Development Group
+.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
+.\"      Date: 2024
+.\"    Manual: PostgreSQL 16.2 Documentation
+.\"    Source: PostgreSQL 16.2
+.\"  Language: English
+.\"
+.TH "SET CONSTRAINTS" "7" "2024" "PostgreSQL 16.2" "PostgreSQL 16.2 Documentation"
+.\" -----------------------------------------------------------------
+.\" * Define some portability stuff
+.\" -----------------------------------------------------------------
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.\" http://bugs.debian.org/507673
+.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.ie \n(.g .ds Aq \(aq
+.el       .ds Aq '
+.\" -----------------------------------------------------------------
+.\" * set default formatting
+.\" -----------------------------------------------------------------
+.\" disable hyphenation
+.nh
+.\" disable justification (adjust text to left margin only)
+.ad l
+.\" -----------------------------------------------------------------
+.\" * MAIN CONTENT STARTS HERE *
+.\" -----------------------------------------------------------------
+.SH "NAME"
+SET_CONSTRAINTS \- set constraint check timing for the current transaction
+.SH "SYNOPSIS"
+.sp
+.nf
+SET CONSTRAINTS { ALL | \fIname\fR [, \&.\&.\&.] } { DEFERRED | IMMEDIATE }
+.fi
+.SH "DESCRIPTION"
+.PP
+\fBSET CONSTRAINTS\fR
+sets the behavior of constraint checking within the current transaction\&.
+IMMEDIATE
+constraints are checked at the end of each statement\&.
+DEFERRED
+constraints are not checked until transaction commit\&. Each constraint has its own
+IMMEDIATE
+or
+DEFERRED
+mode\&.
+.PP
+Upon creation, a constraint is given one of three characteristics:
+DEFERRABLE INITIALLY DEFERRED,
+DEFERRABLE INITIALLY IMMEDIATE, or
+NOT DEFERRABLE\&. The third class is always
+IMMEDIATE
+and is not affected by the
+\fBSET CONSTRAINTS\fR
+command\&. The first two classes start every transaction in the indicated mode, but their behavior can be changed within a transaction by
+\fBSET CONSTRAINTS\fR\&.
+.PP
+\fBSET CONSTRAINTS\fR
+with a list of constraint names changes the mode of just those constraints (which must all be deferrable)\&. Each constraint name can be schema\-qualified\&. The current schema search path is used to find the first matching name if no schema name is specified\&.
+\fBSET CONSTRAINTS ALL\fR
+changes the mode of all deferrable constraints\&.
+.PP
+When
+\fBSET CONSTRAINTS\fR
+changes the mode of a constraint from
+DEFERRED
+to
+IMMEDIATE, the new mode takes effect retroactively: any outstanding data modifications that would have been checked at the end of the transaction are instead checked during the execution of the
+\fBSET CONSTRAINTS\fR
+command\&. If any such constraint is violated, the
+\fBSET CONSTRAINTS\fR
+fails (and does not change the constraint mode)\&. Thus,
+\fBSET CONSTRAINTS\fR
+can be used to force checking of constraints to occur at a specific point in a transaction\&.
+.PP
+Currently, only
+UNIQUE,
+PRIMARY KEY,
+REFERENCES
+(foreign key), and
+EXCLUDE
+constraints are affected by this setting\&.
+NOT NULL
+and
+CHECK
+constraints are always checked immediately when a row is inserted or modified (\fInot\fR
+at the end of the statement)\&. Uniqueness and exclusion constraints that have not been declared
+DEFERRABLE
+are also checked immediately\&.
+.PP
+The firing of triggers that are declared as
+\(lqconstraint triggers\(rq
+is also controlled by this setting \(em they fire at the same time that the associated constraint should be checked\&.
+.SH "NOTES"
+.PP
+Because
+PostgreSQL
+does not require constraint names to be unique within a schema (but only per\-table), it is possible that there is more than one match for a specified constraint name\&. In this case
+\fBSET CONSTRAINTS\fR
+will act on all matches\&. For a non\-schema\-qualified name, once a match or matches have been found in some schema in the search path, schemas appearing later in the path are not searched\&.
+.PP
+This command only alters the behavior of constraints within the current transaction\&. Issuing this outside of a transaction block emits a warning and otherwise has no effect\&.
+.SH "COMPATIBILITY"
+.PP
+This command complies with the behavior defined in the SQL standard, except for the limitation that, in
+PostgreSQL, it does not apply to
+NOT NULL
+and
+CHECK
+constraints\&. Also,
+PostgreSQL
+checks non\-deferrable uniqueness constraints immediately, not at end of statement as the standard would suggest\&.