From fc22b6623b6b3bab3cb057ccd282c2bfad1a0b30 Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Sat, 30 Mar 2019 08:13:09 +0100 Subject: Generated columns 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 Reviewed-by: Pavel Stehule Discussion: https://www.postgresql.org/message-id/flat/b151f851-4019-bdb1-699e-ebab07d2f40a@2ndquadrant.com --- src/backend/parser/parse_utilcmd.c | 66 +++++++++++++++++++++++++++++++++++--- 1 file changed, 62 insertions(+), 4 deletions(-) (limited to 'src/backend/parser/parse_utilcmd.c') diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c index 8fdd3d785c7..674f4b98f40 100644 --- a/src/backend/parser/parse_utilcmd.c +++ b/src/backend/parser/parse_utilcmd.c @@ -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); + def->cooked_default = map_variable_attnos(this_default, + 1, 0, + attmap, tupleDesc->natts, + InvalidOid, &found_whole_row); + /* - * 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. + * 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)))); - def->cooked_default = this_default; + if (attribute->attgenerated && + (table_like_clause->options & CREATE_TABLE_LIKE_GENERATED)) + def->generated = attribute->attgenerated; } /* -- cgit v1.2.3