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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

27
src/backend/parser/analyze.c
View File

@ -2287,6 +2287,7 @@ transformUpdateTargetList(ParseState *pstate, List *origTlist)
RangeTblEntry *target_rte;
ListCell *orig_tl;
ListCell *tl;
TupleDesc tupdesc = pstate->p_target_relation->rd_att;
tlist = transformTargetList(pstate, origTlist,
EXPR_KIND_UPDATE_SOURCE);
@ -2345,6 +2346,32 @@ transformUpdateTargetList(ParseState *pstate, List *origTlist)
if (orig_tl != NULL)
elog(ERROR, "UPDATE target count mismatch --- internal error");
/*
* Record in extraUpdatedCols generated columns referencing updated base
* columns.
*/
if (tupdesc->constr &&
tupdesc->constr->has_generated_stored)
{
for (int i = 0; i < tupdesc->constr->num_defval; i++)
{
AttrDefault defval = tupdesc->constr->defval[i];
Node *expr;
Bitmapset *attrs_used = NULL;
/* skip if not generated column */
if (!TupleDescAttr(tupdesc, defval.adnum - 1)->attgenerated)
continue;
expr = stringToNode(defval.adbin);
pull_varattnos(expr, 1, &attrs_used);
if (bms_overlap(target_rte->updatedCols, attrs_used))
target_rte->extraUpdatedCols = bms_add_member(target_rte->extraUpdatedCols,
defval.adnum - FirstLowInvalidHeapAttributeNumber);
}
}
return tlist;
}

14
src/backend/parser/gram.y
View File

@ -681,7 +681,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
SAVEPOINT SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
SERIALIZABLE SERVER SESSION SESSION_USER SET SETS SETOF SHARE SHOW
SIMILAR SIMPLE SKIP SMALLINT SNAPSHOT SOME SQL_P STABLE STANDALONE_P
START STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P
START STATEMENT STATISTICS STDIN STDOUT STORAGE STORED STRICT_P STRIP_P
SUBSCRIPTION SUBSTRING SUPPORT SYMMETRIC SYSID SYSTEM_P
TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
@ -3497,6 +3497,16 @@ ColConstraintElem:
n->location = @1;
$$ = (Node *)n;
}
| GENERATED generated_when AS '(' a_expr ')' STORED
{
Constraint *n = makeNode(Constraint);
n->contype = CONSTR_GENERATED;
n->generated_when = $2;
n->raw_expr = $5;
n->cooked_expr = NULL;
n->location = @1;
$$ = (Node *)n;
}
| REFERENCES qualified_name opt_column_list key_match key_actions
{
Constraint *n = makeNode(Constraint);
@ -3587,6 +3597,7 @@ TableLikeOption:
| CONSTRAINTS { $$ = CREATE_TABLE_LIKE_CONSTRAINTS; }
| DEFAULTS { $$ = CREATE_TABLE_LIKE_DEFAULTS; }
| IDENTITY_P { $$ = CREATE_TABLE_LIKE_IDENTITY; }
| GENERATED { $$ = CREATE_TABLE_LIKE_GENERATED; }
| INDEXES { $$ = CREATE_TABLE_LIKE_INDEXES; }
| STATISTICS { $$ = CREATE_TABLE_LIKE_STATISTICS; }
| STORAGE { $$ = CREATE_TABLE_LIKE_STORAGE; }
@ -15234,6 +15245,7 @@ unreserved_keyword:
| STDIN
| STDOUT
| STORAGE
| STORED
| STRICT_P
| STRIP_P
| SUBSCRIPTION

11
src/backend/parser/parse_agg.c
View File

@ -520,6 +520,14 @@ check_agglevels_and_constraints(ParseState *pstate, Node *expr)
err = _("grouping operations are not allowed in partition key expressions");
break;
case EXPR_KIND_GENERATED_COLUMN:
if (isAgg)
err = _("aggregate functions are not allowed in column generation expressions");
else
err = _("grouping operations are not allowed in column generation expressions");
break;
case EXPR_KIND_CALL_ARGUMENT:
if (isAgg)
@ -922,6 +930,9 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
case EXPR_KIND_COPY_WHERE:
err = _("window functions are not allowed in COPY FROM WHERE conditions");
break;
case EXPR_KIND_GENERATED_COLUMN:
err = _("window functions are not allowed in column generation expressions");
break;
/*
* There is intentionally no default: case here, so that the

6
src/backend/parser/parse_expr.c
View File

@ -570,6 +570,7 @@ transformColumnRef(ParseState *pstate, ColumnRef *cref)
case EXPR_KIND_PARTITION_EXPRESSION:
case EXPR_KIND_CALL_ARGUMENT:
case EXPR_KIND_COPY_WHERE:
case EXPR_KIND_GENERATED_COLUMN:
/* okay */
break;
@ -1927,6 +1928,9 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
case EXPR_KIND_COPY_WHERE:
err = _("cannot use subquery in COPY FROM WHERE condition");
break;
case EXPR_KIND_GENERATED_COLUMN:
err = _("cannot use subquery in column generation expression");
break;
/*
* There is intentionally no default: case here, so that the
@ -3557,6 +3561,8 @@ ParseExprKindName(ParseExprKind exprKind)
return "CALL";
case EXPR_KIND_COPY_WHERE:
return "WHERE";
case EXPR_KIND_GENERATED_COLUMN:
return "GENERATED AS";
/*
* There is intentionally no default: case here, so that the

3
src/backend/parser/parse_func.c
View File

@ -2526,6 +2526,9 @@ check_srf_call_placement(ParseState *pstate, Node *last_srf, int location)
case EXPR_KIND_COPY_WHERE:
err = _("set-returning functions are not allowed in COPY FROM WHERE conditions");
break;
case EXPR_KIND_GENERATED_COLUMN:
err = _("set-returning functions are not allowed in column generation expressions");
break;
/*
* There is intentionally no default: case here, so that the

19
src/backend/parser/parse_relation.c
View File

@ -731,6 +731,17 @@ scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte, const char *colname,
colname),
parser_errposition(pstate, location)));
/*
* In generated column, no system column is allowed except tableOid.
*/
if (pstate->p_expr_kind == EXPR_KIND_GENERATED_COLUMN &&
attnum < InvalidAttrNumber && attnum != TableOidAttributeNumber)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
errmsg("cannot use system column \"%s\" in column generation expression",
colname),
parser_errposition(pstate, location)));
if (attnum != InvalidAttrNumber)
{
/* now check to see if column actually is defined */
@ -1257,6 +1268,7 @@ addRangeTableEntry(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list
@ -1328,6 +1340,7 @@ addRangeTableEntryForRelation(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list
@ -1407,6 +1420,7 @@ addRangeTableEntryForSubquery(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list
@ -1670,6 +1684,7 @@ addRangeTableEntryForFunction(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list
@ -1733,6 +1748,7 @@ addRangeTableEntryForTableFunc(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list
@ -1811,6 +1827,7 @@ addRangeTableEntryForValues(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list
@ -1881,6 +1898,7 @@ addRangeTableEntryForJoin(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list
@ -1983,6 +2001,7 @@ addRangeTableEntryForCTE(ParseState *pstate,
rte->selectedCols = NULL;
rte->insertedCols = NULL;
rte->updatedCols = NULL;
rte->extraUpdatedCols = NULL;
/*
* Add completed RTE to pstate's range table list, but not to join list

70
src/backend/parser/parse_utilcmd.c
View File

@ -502,6 +502,7 @@ transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
bool saw_nullable;
bool saw_default;
bool saw_identity;
bool saw_generated;
ListCell *clist;
cxt->columns = lappend(cxt->columns, column);
@ -609,6 +610,7 @@ transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
saw_nullable = false;
saw_default = false;
saw_identity = false;
saw_generated = false;
foreach(clist, column->constraints)
{
@ -689,6 +691,29 @@ transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
break;
}
case CONSTR_GENERATED:
if (cxt->ofType)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("generated columns are not supported on typed tables")));
if (cxt->partbound)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("generated columns are not supported on partitions")));
if (saw_generated)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("multiple generation clauses specified for column \"%s\" of table \"%s\"",
column->colname, cxt->relation->relname),
parser_errposition(cxt->pstate,
constraint->location)));
column->generated = ATTRIBUTE_GENERATED_STORED;
column->raw_default = constraint->raw_expr;
Assert(constraint->cooked_expr == NULL);
saw_generated = true;
break;
case CONSTR_CHECK:
cxt->ckconstraints = lappend(cxt->ckconstraints, constraint);
break;
@ -755,6 +780,22 @@ transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
column->colname, cxt->relation->relname),
parser_errposition(cxt->pstate,
constraint->location)));
if (saw_default && saw_generated)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("both default and generation expression specified for column \"%s\" of table \"%s\"",
column->colname, cxt->relation->relname),
parser_errposition(cxt->pstate,
constraint->location)));
if (saw_identity && saw_generated)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("both identity and generation expression specified for column \"%s\" of table \"%s\"",
column->colname, cxt->relation->relname),
parser_errposition(cxt->pstate,
constraint->location)));
}
/*
@ -983,11 +1024,13 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
* Copy default, if present and the default has been requested
*/
if (attribute->atthasdef &&
(table_like_clause->options & CREATE_TABLE_LIKE_DEFAULTS))
(table_like_clause->options & CREATE_TABLE_LIKE_DEFAULTS ||
table_like_clause->options & CREATE_TABLE_LIKE_GENERATED))
{
Node *this_default = NULL;
AttrDefault *attrdef;
int i;
bool found_whole_row;
/* Find default in constraint structure */
Assert(constr != NULL);
@ -1002,12 +1045,27 @@ transformTableLikeClause(CreateStmtContext *cxt, TableLikeClause *table_like_cla
}
Assert(this_default != NULL);
/*
* If default expr could contain any vars, we'd need to fix 'em,
* but it can't; so default is ready to apply to child.
*/
def->cooked_default = map_variable_attnos(this_default,
1, 0,
attmap, tupleDesc->natts,
InvalidOid, &found_whole_row);
def->cooked_default = this_default;
/*
* Prevent this for the same reason as for constraints below.
* Note that defaults cannot contain any vars, so it's OK that the
* error message refers to generated columns.
*/
if (found_whole_row)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot convert whole-row table reference"),
errdetail("Generation expression for column \"%s\" contains a whole-row reference to table \"%s\".",
attributeName,
RelationGetRelationName(relation))));
if (attribute->attgenerated &&
(table_like_clause->options & CREATE_TABLE_LIKE_GENERATED))
def->generated = attribute->attgenerated;
}
/*