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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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33
src/backend/utils/cache/lsyscache.c vendored
View File

@ -821,6 +821,39 @@ get_attnum(Oid relid, const char *attname)
return InvalidAttrNumber;
}
/*
* get_attgenerated
*
* Given the relation id and the attribute name,
* return the "attgenerated" field from the attribute relation.
*
* Errors if not found.
*
* Since not generated is represented by '\0', this can also be used as a
* Boolean test.
*/
char
get_attgenerated(Oid relid, AttrNumber attnum)
{
HeapTuple tp;
tp = SearchSysCache2(ATTNUM,
ObjectIdGetDatum(relid),
Int16GetDatum(attnum));
if (HeapTupleIsValid(tp))
{
Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
char result;
result = att_tup->attgenerated;
ReleaseSysCache(tp);
return result;
}
else
elog(ERROR, "cache lookup failed for attribute %d of relation %u",
attnum, relid);
}
/*
* get_atttype
*

1
src/backend/utils/cache/partcache.c vendored
View File

@ -27,6 +27,7 @@
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "partitioning/partbounds.h"
#include "rewrite/rewriteHandler.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"

4
src/backend/utils/cache/relcache.c vendored
View File

@ -515,6 +515,7 @@ RelationBuildTupleDesc(Relation relation)
constr = (TupleConstr *) MemoryContextAlloc(CacheMemoryContext,
sizeof(TupleConstr));
constr->has_not_null = false;
constr->has_generated_stored = false;
/*
* Form a scan key that selects only user attributes (attnum > 0).
@ -567,6 +568,8 @@ RelationBuildTupleDesc(Relation relation)
/* Update constraint/default info */
if (attp->attnotnull)
constr->has_not_null = true;
if (attp->attgenerated == ATTRIBUTE_GENERATED_STORED)
constr->has_generated_stored = true;
/* If the column has a default, fill it into the attrdef array */
if (attp->atthasdef)
@ -3281,6 +3284,7 @@ RelationBuildLocalRelation(const char *relname,
Form_pg_attribute datt = TupleDescAttr(rel->rd_att, i);
datt->attidentity = satt->attidentity;
datt->attgenerated = satt->attgenerated;
datt->attnotnull = satt->attnotnull;
has_not_null |= satt->attnotnull;
}