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Generated columns

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This is an SQL-standard feature that allows creating columns that are
computed from expressions rather than assigned, similar to a view or
materialized view but on a column basis.

This implements one kind of generated column: stored (computed on
write).  Another kind, virtual (computed on read), is planned for the
future, and some room is left for it.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/b151f851-4019-bdb1-699e-ebab07d2f40a@2ndquadrant.com
This commit is contained in:
Peter Eisentraut
2019-03-30 08:13:09 +01:00
parent 6b8b5364dd
commit fc22b6623b
84 changed files with 3067 additions and 157 deletions
Download Patch File Download Diff File Expand all files Collapse all files

36
src/backend/rewrite/rewriteHandler.c
View File

@ -818,6 +818,13 @@ rewriteTargetListIU(List *targetList,
if (att_tup->attidentity == ATTRIBUTE_IDENTITY_BY_DEFAULT && override == OVERRIDING_USER_VALUE)
apply_default = true;
if (att_tup->attgenerated && !apply_default)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("cannot insert into column \"%s\"", NameStr(att_tup->attname)),
errdetail("Column \"%s\" is a generated column.",
NameStr(att_tup->attname))));
}
if (commandType == CMD_UPDATE)
@ -828,9 +835,23 @@ rewriteTargetListIU(List *targetList,
errmsg("column \"%s\" can only be updated to DEFAULT", NameStr(att_tup->attname)),
errdetail("Column \"%s\" is an identity column defined as GENERATED ALWAYS.",
NameStr(att_tup->attname))));
if (att_tup->attgenerated && new_tle && !apply_default)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("column \"%s\" can only be updated to DEFAULT", NameStr(att_tup->attname)),
errdetail("Column \"%s\" is a generated column.",
NameStr(att_tup->attname))));
}
if (apply_default)
if (att_tup->attgenerated)
{
/*
* stored generated column will be fixed in executor
*/
new_tle = NULL;
}
else if (apply_default)
{
Node *new_expr;
@ -1137,13 +1158,12 @@ build_column_default(Relation rel, int attrno)
}
}
if (expr == NULL)
{
/*
* No per-column default, so look for a default for the type itself.
*/
/*
* No per-column default, so look for a default for the type itself. But
* not for generated columns.
*/
if (expr == NULL && !att_tup->attgenerated)
expr = get_typdefault(atttype);
}
if (expr == NULL)
return NULL; /* No default anywhere */
@ -1720,12 +1740,14 @@ ApplyRetrieveRule(Query *parsetree,
subrte->selectedCols = rte->selectedCols;
subrte->insertedCols = rte->insertedCols;
subrte->updatedCols = rte->updatedCols;
subrte->extraUpdatedCols = rte->extraUpdatedCols;
rte->requiredPerms = 0; /* no permission check on subquery itself */
rte->checkAsUser = InvalidOid;
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
return parsetree;
}