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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
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6
src/backend/parser/parse_expr.c
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@@ -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