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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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112
src/backend/executor/nodeModifyTable.c
View File

@ -49,6 +49,7 @@
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "rewrite/rewriteHandler.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "utils/builtins.h"
@ -240,6 +241,89 @@ ExecCheckTIDVisible(EState *estate,
ExecClearTuple(tempSlot);
}
/*
* Compute stored generated columns for a tuple
*/
void
ExecComputeStoredGenerated(EState *estate, TupleTableSlot *slot)
{
ResultRelInfo *resultRelInfo = estate->es_result_relation_info;
Relation rel = resultRelInfo->ri_RelationDesc;
TupleDesc tupdesc = RelationGetDescr(rel);
int natts = tupdesc->natts;
MemoryContext oldContext;
Datum *values;
bool *nulls;
bool *replaces;
HeapTuple oldtuple, newtuple;
bool should_free;
Assert(tupdesc->constr && tupdesc->constr->has_generated_stored);
/*
* If first time through for this result relation, build expression
* nodetrees for rel's stored generation expressions. Keep them in the
* per-query memory context so they'll survive throughout the query.
*/
if (resultRelInfo->ri_GeneratedExprs == NULL)
{
oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
resultRelInfo->ri_GeneratedExprs =
(ExprState **) palloc(natts * sizeof(ExprState *));
for (int i = 0; i < natts; i++)
{
if (TupleDescAttr(tupdesc, i)->attgenerated == ATTRIBUTE_GENERATED_STORED)
{
Expr *expr;
expr = (Expr *) build_column_default(rel, i + 1);
if (expr == NULL)
elog(ERROR, "no generation expression found for column number %d of table \"%s\"",
i + 1, RelationGetRelationName(rel));
resultRelInfo->ri_GeneratedExprs[i] = ExecPrepareExpr(expr, estate);
}
}
MemoryContextSwitchTo(oldContext);
}
oldContext = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
values = palloc(sizeof(*values) * natts);
nulls = palloc(sizeof(*nulls) * natts);
replaces = palloc0(sizeof(*replaces) * natts);
for (int i = 0; i < natts; i++)
{
if (TupleDescAttr(tupdesc, i)->attgenerated == ATTRIBUTE_GENERATED_STORED)
{
ExprContext *econtext;
Datum val;
bool isnull;
econtext = GetPerTupleExprContext(estate);
econtext->ecxt_scantuple = slot;
val = ExecEvalExpr(resultRelInfo->ri_GeneratedExprs[i], econtext, &isnull);
values[i] = val;
nulls[i] = isnull;
replaces[i] = true;
}
}
oldtuple = ExecFetchSlotHeapTuple(slot, true, &should_free);
newtuple = heap_modify_tuple(oldtuple, tupdesc, values, nulls, replaces);
ExecForceStoreHeapTuple(newtuple, slot);
if (should_free)
heap_freetuple(oldtuple);
MemoryContextSwitchTo(oldContext);
}
/* ----------------------------------------------------------------
* ExecInsert
*
@ -297,6 +381,13 @@ ExecInsert(ModifyTableState *mtstate,
}
else if (resultRelInfo->ri_FdwRoutine)
{
/*
* Compute stored generated columns
*/
if (resultRelationDesc->rd_att->constr &&
resultRelationDesc->rd_att->constr->has_generated_stored)
ExecComputeStoredGenerated(estate, slot);
/*
* insert into foreign table: let the FDW do it
*/
@ -326,6 +417,13 @@ ExecInsert(ModifyTableState *mtstate,
*/
slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
/*
* Compute stored generated columns
*/
if (resultRelationDesc->rd_att->constr &&
resultRelationDesc->rd_att->constr->has_generated_stored)
ExecComputeStoredGenerated(estate, slot);
/*
* Check any RLS WITH CHECK policies.
*
@ -964,6 +1062,13 @@ ExecUpdate(ModifyTableState *mtstate,
}
else if (resultRelInfo->ri_FdwRoutine)
{
/*
* Compute stored generated columns
*/
if (resultRelationDesc->rd_att->constr &&
resultRelationDesc->rd_att->constr->has_generated_stored)
ExecComputeStoredGenerated(estate, slot);
/*
* update in foreign table: let the FDW do it
*/
@ -994,6 +1099,13 @@ ExecUpdate(ModifyTableState *mtstate,
*/
slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
/*
* Compute stored generated columns
*/
if (resultRelationDesc->rd_att->constr &&
resultRelationDesc->rd_att->constr->has_generated_stored)
ExecComputeStoredGenerated(estate, slot);
/*
* Check any RLS UPDATE WITH CHECK policies
*