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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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31
src/backend/commands/copy.c
View File

@ -32,6 +32,7 @@
#include "commands/trigger.h"
#include "executor/execPartition.h"
#include "executor/executor.h"
#include "executor/nodeModifyTable.h"
#include "executor/tuptable.h"
#include "foreign/fdwapi.h"
#include "libpq/libpq.h"
@ -2922,6 +2923,21 @@ CopyFrom(CopyState cstate)
}
else
{
/*
* Compute stored generated columns
*
* Switch memory context so that the new tuple is in the same
* context as the old one.
*/
if (resultRelInfo->ri_RelationDesc->rd_att->constr &&
resultRelInfo->ri_RelationDesc->rd_att->constr->has_generated_stored)
{
ExecComputeStoredGenerated(estate, slot);
MemoryContextSwitchTo(batchcontext);
tuple = ExecCopySlotHeapTuple(slot);
MemoryContextSwitchTo(oldcontext);
}
/*
* If the target is a plain table, check the constraints of
* the tuple.
@ -3271,7 +3287,7 @@ BeginCopyFrom(ParseState *pstate,
fmgr_info(in_func_oid, &in_functions[attnum - 1]);
/* Get default info if needed */
if (!list_member_int(cstate->attnumlist, attnum))
if (!list_member_int(cstate->attnumlist, attnum) && !att->attgenerated)
{
/* attribute is NOT to be copied from input */
/* use default value if one exists */
@ -4876,6 +4892,11 @@ CopyAttributeOutCSV(CopyState cstate, char *string,
* or NIL if there was none (in which case we want all the non-dropped
* columns).
*
* We don't include generated columns in the generated full list and we don't
* allow them to be specified explicitly. They don't make sense for COPY
* FROM, but we could possibly allow them for COPY TO. But this way it's at
* least ensured that whatever we copy out can be copied back in.
*
* rel can be NULL ... it's only used for error reports.
*/
static List *
@ -4893,6 +4914,8 @@ CopyGetAttnums(TupleDesc tupDesc, Relation rel, List *attnamelist)
{
if (TupleDescAttr(tupDesc, i)->attisdropped)
continue;
if (TupleDescAttr(tupDesc, i)->attgenerated)
continue;
attnums = lappend_int(attnums, i + 1);
}
}
@ -4917,6 +4940,12 @@ CopyGetAttnums(TupleDesc tupDesc, Relation rel, List *attnamelist)
continue;
if (namestrcmp(&(att->attname), name) == 0)
{
if (att->attgenerated)
ereport(ERROR,
(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
errmsg("column \"%s\" is a generated column",
name),
errdetail("Generated columns cannot be used in COPY.")));
attnum = att->attnum;
break;
}