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versioning.c
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/* -------------------------------------------------------------------------
*
* versioning.c
*
* Copyright (c) 2012-2017 Vladislav Arkhipov <[email protected]>
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include <math.h>
#include <float.h>
#if PG_VERSION_NUM >= 90300
#include "access/htup_details.h"
#endif
#include "access/xact.h"
#include "catalog/namespace.h"
#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "executor/spi.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rangetypes.h"
#if PG_VERSION_NUM >= 100000
#include "utils/regproc.h"
#endif
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/timestamp.h"
#include "temporal_tables.h"
#if defined(_MSC_VER) && (_MSC_VER < 1800)
#define nextafter(x, y) _nextafter(x, y)
#endif
PGDLLEXPORT Datum versioning(PG_FUNCTION_ARGS);
PGDLLEXPORT Datum set_system_time(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(versioning);
PG_FUNCTION_INFO_V1(set_system_time);
/* Warning if system period was adjusted. */
#define ERRCODE_WARNING_SYSTEM_PERIOD_ADJUSTED MAKE_SQLSTATE('0', '1', 'X', '0', '1')
/* Cached data for versioning trigger. */
typedef struct VersioningHashEntry
{
Oid relid; /* hash key (must be first) */
Oid history_relid; /* OID of the history relation */
TupleDesc tupdesc; /* tuple descriptor of the versioned relation */
TupleDesc history_tupdesc; /* tuple descriptor of the history relation */
/*
* The number of items in attnums or -1 if this cached data is invalid.
* If attnums is not zero then tupdesc, history_tupdesc, attnums and
* insert_history_plan contains not null values.
*/
int natts;
/*
* attnums[N] is a number of attribute in the versioned relation that is
* also appears in the history relation.
*/
int *attnums;
/* Cached plan of INSERT command into the history relation. */
SPIPlanPtr insert_history_plan;
} VersioningHashEntry;
/* true if datetimes are integer based. */
static bool integer_datetimes;
/* true if integer_datetimes value was looked up. */
static bool integer_datetimes_set = false;
/* Contains cached data for OID of versioned relation. */
static HTAB *versioning_cache = NULL;
static bool parse_adjust_argument(const char *arg);
/*
* Local function prototypes.
*/
static TypeCacheEntry *get_period_typcache(FunctionCallInfo fcinfo,
Form_pg_attribute attr,
Relation relation);
static void check_attr_type(Form_pg_attribute attr,
Form_pg_attribute history_attr,
Relation relation,
Relation history_relation);
static void fill_versioning_hash_entry(VersioningHashEntry *hash_entry,
Relation relation,
Relation history_relation,
TupleDesc tupdesc,
const char *period_attname);
static void insert_history_row(HeapTuple tuple,
Relation relation,
const char *history_relation_argument,
const char *period_attname);
static void deserialize_system_period(HeapTuple tuple,
Relation relation,
int period_attnum,
const char *period_attname,
TypeCacheEntry *typcache,
RangeBound *lower,
RangeBound *upper);
static void lookup_integer_datetimes();
static TimestampTz get_system_time();
static TimestampTz next_timestamp(TimestampTz timestamp);
static void adjust_system_period(TypeCacheEntry *typcache,
RangeBound *lower,
RangeBound *upper,
const char *adjust_argument,
Relation relation);
static bool modified_in_current_transaction(HeapTuple tuple);
static HeapTuple modify_tuple(Relation rel, HeapTuple tuple,
int period_attnum, RangeType *range);
static Datum versioning_insert(TriggerData *trigdata,
TypeCacheEntry *typcache,
int period_attnum);
static Datum versioning_update(TriggerData *trigdata,
TypeCacheEntry *typcache,
int period_attnum,
const char *period_attname,
const char *history_relation_argument,
const char *adjust_argument);
static Datum versioning_delete(TriggerData *trigdata,
TypeCacheEntry *typcache,
int period_attnum,
const char *period_attname,
const char *history_relation_argument,
const char *adjust_argument);
static void init_versioning_hash_table();
static void *hash_entry_alloc(Size size);
static VersioningHashEntry *lookup_versioning_hash_entry(Oid relid,
bool *found);
/*
* This trigger maintains the logic of versioned tables.
*
* Versioned table contains the current active rows. Archived rows are located
* into the other table called the history table. When you insert, update or
* delete rows in the versioned table, the current trigger automatically
* inserts a copy of the old row into the corresponding history table.
*
* Versioned table must contains a special column of type tstzrange called
* the system period. The begin of this period represents the time when the
* row data became current. The end of this period represents the time when
* the row data was no longer current.
*
* The common history table columns and versioned table columns must have the
* same data types.
*
* To convert a table to a system versioned table:
* 1. Create a system period column in the original table.
* 2. Create a history table.
* 3. Use CREATE TRIGGER on the original table as shown below.
*
* In CREATE TRIGGER you are to specify a system period column name, a history
* relation name and "adjust" parameter:
*
* CREATE TRIGGER <trigger_name>
* BEFORE INSERT OR UPDATE OR DELETE ON <versioned_table>
* FOR EACH ROW EXECUTE PROCEDURE
* versioning(<system_period_column_name>, <history_relation>, <adjust>).
*/
Datum
versioning(PG_FUNCTION_ARGS)
{
TriggerData *trigdata;
Trigger *trigger;
char **args;
Relation relation;
TupleDesc tupdesc;
char *period_attname;
int period_attnum;
Form_pg_attribute period_attr;
TypeCacheEntry *typcache;
trigdata = (TriggerData *) fcinfo->context;
/* Check that the trigger function was called in expected context. */
if (!CALLED_AS_TRIGGER(fcinfo))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("function \"versioning\" was not called by trigger manager")));
/* Check proper event. */
if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event) ||
!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("function \"versioning\" must be fired BEFORE ROW")));
if (!TRIGGER_FIRED_BY_INSERT(trigdata->tg_event) &&
!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event) &&
!TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("function \"versioning\" must be fired for INSERT or UPDATE or DELETE")));
trigger = trigdata->tg_trigger;
/* Check number of arguments. */
if (trigger->tgnargs != 3)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("wrong number of parameters for function \"versioning\""),
errdetail("expected 3 parameters but got %d",
trigger->tgnargs)));
args = trigger->tgargs;
relation = trigdata->tg_relation;
tupdesc = RelationGetDescr(relation);
period_attname = args[0];
/* Check that system period attribute exists in the versioned relation. */
period_attnum = SPI_fnumber(tupdesc, period_attname);
if (period_attnum == SPI_ERROR_NOATTRIBUTE)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("column \"%s\" of relation \"%s\" does not exist",
period_attname,
RelationGetRelationName(relation))));
period_attr = tupdesc->attrs[period_attnum - 1];
/* Check that system period attribute is not dropped. */
if (period_attr->attisdropped)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("column \"%s\" of relation \"%s\" does not exist",
period_attname,
RelationGetRelationName(relation))));
/* Check that system period attribute is not an array. */
if (period_attr->attndims != 0)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("system period column \"%s\" of relation \"%s\" is not a range but an array",
period_attname,
RelationGetRelationName(relation))));
/* Locate the typcache entry for the type of system period attribute. */
typcache = get_period_typcache(fcinfo, period_attr, relation);
if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
return versioning_insert(trigdata, typcache, period_attnum);
else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
return versioning_update(trigdata, typcache,
period_attnum, period_attname,
args[1], args[2]);
else
/* otherwise this is ON DELETE trigger */
return versioning_delete(trigdata, typcache,
period_attnum, period_attname,
args[1], args[2]);
}
/*
* Set the system time value that is used by versioned triggers to the
* specific value. Revert to the default behaviour if NULL is passed for the
* argument.
*/
Datum
set_system_time(PG_FUNCTION_ARGS)
{
TemporalContext *ctx = get_current_temporal_context(true);
if (PG_ARGISNULL(0))
{
ctx->system_time_mode = CurrentTransactionStartTimestamp;
}
else
{
ctx->system_time_mode = UserDefined;
ctx->system_time = PG_GETARG_TIMESTAMPTZ(0);
}
PG_RETURN_VOID();
}
/*
* Get the value that should be used as the system time by versioned
* triggers.
*/
static TimestampTz
get_system_time()
{
TemporalContext *ctx = get_current_temporal_context(false);
switch (ctx->system_time_mode)
{
case CurrentTransactionStartTimestamp:
return GetCurrentTransactionStartTimestamp();
case UserDefined:
return ctx->system_time;
}
Assert(false);
/* will never get here */
return 0;
}
/*
* Parse argument value as boolean. The valid values are "true" for true,
* "false" for false.
*
* If the string parses okay, return the parsed value, else throw an error.
*/
static bool
parse_adjust_argument(const char *arg)
{
if (pg_strcasecmp(arg, "true") == 0)
return true;
if (pg_strcasecmp(arg, "false") == 0)
return false;
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid value \"%s\" for \"adjust\" parameter",
arg),
errdetail("valid values are: \"true\", \"false\"")));
return false;
}
/*
* Locate the typcache entry for the system period attribute. If the specified
* attribute is not a range of timestamp with timezone, an error is thrown.
*/
static TypeCacheEntry *
get_period_typcache(FunctionCallInfo fcinfo,
Form_pg_attribute attr,
Relation relation)
{
Oid typoid;
HeapTuple type_tuple;
Form_pg_type type;
TypeCacheEntry *typcache;
typoid = attr->atttypid;
/* Search syscache for attribute type. */
type_tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typoid));
if (!HeapTupleIsValid(type_tuple))
elog(ERROR, "cache lookup failed for type %u", typoid);
type = (Form_pg_type) GETSTRUCT(type_tuple);
/* Check that type is a range. */
if (type->typtype != TYPTYPE_RANGE)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("system period column \"%s\" of relation \"%s\" is not a range but type %s",
NameStr(attr->attname),
RelationGetRelationName(relation),
format_type_be(typoid))));
/* Get cached information about the range type. */
typcache = range_get_typcache(fcinfo, typoid);
/* Check that this is a range of timestamp with timezone. */
if (typcache->rngelemtype->type_id != TIMESTAMPTZOID)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("system period column \"%s\" of relation \"%s\" is not a range of timestamp with timezone but of type %s",
NameStr(attr->attname),
RelationGetRelationName(relation),
format_type_be(typcache->rngelemtype->type_id))));
ReleaseSysCache(type_tuple);
return typcache;
}
/*
* Check that the type of an attribute in the versioned table is the same as in
* the history table.
*/
static void
check_attr_type(Form_pg_attribute attr,
Form_pg_attribute history_attr,
Relation relation,
Relation history_relation)
{
if (attr->atttypid != history_attr->atttypid ||
attr->attndims != history_attr->attndims ||
attr->atttypmod != history_attr->atttypmod)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("column \"%s\" of relation \"%s\" is of type %s but column \"%s\" of history relation \"%s\" is of type %s",
NameStr(attr->attname),
RelationGetRelationName(relation),
format_type_with_typemod(attr->atttypid,
attr->atttypmod),
NameStr(history_attr->attname),
RelationGetRelationName(history_relation),
format_type_with_typemod(history_attr->atttypid,
history_attr->atttypmod))));
}
/*
* Fill a newly created hash entry with the cached data.
*
* Note that hash entry must be zeroed and natts value of the entry must be
* set to -1 prior to the call of this function.
*/
static void
fill_versioning_hash_entry(VersioningHashEntry *hash_entry,
Relation relation,
Relation history_relation,
TupleDesc tupdesc,
const char *period_attname)
{
TupleDesc history_tupdesc;
MemoryContext oldcontext;
int attnums_size;
int *attnums;
StringInfoData querybuf;
char *nspname;
char *relname;
int *history_attnums;
int natts;
int i;
int ret;
history_tupdesc = RelationGetDescr(history_relation);
/* Check that the history relation contains the system period attribute. */
if (SPI_fnumber(history_tupdesc, period_attname) < 0)
ereport(ERROR,
(errmsg("history relation \"%s\" does not contain system period column \"%s\"",
RelationGetRelationName(history_relation),
period_attname),
errhint("history relation must contain system period column with the same name and data type as the versioned one")));
/*
* Allocate versioned relation attributes array. attnums[N] contains the
* number of the attribute in the versioned relation.
*/
attnums_size = Min(tupdesc->natts, history_tupdesc->natts);
attnums = palloc(attnums_size * sizeof(int));
/*
* The query string build is
* INSERT INTO <history_relation> (<attr1>, <attr2>, ...)
* VALUES ($1, $2, ...)
*/
initStringInfo(&querybuf);
nspname = get_namespace_name(RelationGetNamespace(history_relation));
relname = RelationGetRelationName(history_relation);
appendStringInfo(&querybuf,
"INSERT INTO %s.%s (",
quote_identifier(nspname),
quote_identifier(relname));
/*
* Allocate history relation attributes array. history_attnums[N] is a
* number of the attribute in the history relation that has the same name
* as the attribute with the number attnums[N] in the versioned relation.
*/
history_attnums = palloc(attnums_size * sizeof(int));
/* Fill in common attributes array. */
natts = 0;
for (i = 0; i < tupdesc->natts; ++i)
{
Form_pg_attribute attr;
Form_pg_attribute history_attr;
int history_attnum;
char *attname;
attr = tupdesc->attrs[i];
if (attr->attisdropped)
continue;
attname = NameStr(attr->attname);
history_attnum = SPI_fnumber(history_tupdesc, attname);
if (history_attnum < 0)
continue;
history_attr = history_tupdesc->attrs[history_attnum - 1];
check_attr_type(attr, history_attr, relation, history_relation);
attnums[natts] = attr->attnum;
history_attnums[natts] = history_attnum;
if (natts != 0)
appendStringInfo(&querybuf, ", ");
appendStringInfo(&querybuf, "%s", quote_identifier(attname));
natts++;
}
/*
* If there are common attributes, then prepare and set the plan and
* related information.
*/
if (natts != 0)
{
Oid *argtypes;
SPIPlanPtr plan;
appendStringInfo(&querybuf, ") VALUES (");
argtypes = palloc(sizeof(Oid) * natts);
for (i = 0; i < natts; ++i)
{
if (i != 0)
appendStringInfo(&querybuf, ", ");
appendStringInfo(&querybuf, "$%d", i + 1);
argtypes[i] = SPI_gettypeid(history_tupdesc, history_attnums[i]);
}
appendStringInfo(&querybuf, ")");
/* Prepare and save the plan. */
plan = SPI_prepare(querybuf.data, natts, argtypes);
if (plan == NULL)
elog(ERROR, "SPI_prepare returned %d for %s",
SPI_result, NameStr(querybuf));
if ((ret = SPI_keepplan(plan)) != 0)
elog(ERROR, "SPI_keepplan returned %d", ret);
hash_entry->insert_history_plan = plan;
pfree(argtypes);
/* Copy the constructed attribute list into TopMemoryContext. */
oldcontext = MemoryContextSwitchTo(TopMemoryContext);
hash_entry->history_relid = RelationGetRelid(history_relation);
hash_entry->tupdesc = CreateTupleDescCopyConstr(tupdesc);
hash_entry->history_tupdesc = CreateTupleDescCopyConstr(history_tupdesc);
hash_entry->attnums = palloc(natts * sizeof(int));
memcpy(hash_entry->attnums, attnums, natts * sizeof(int));
MemoryContextSwitchTo(oldcontext);
}
/*
* Now when the cached data structure is filled we can set natts to mark
* the entry valid.
*/
hash_entry->natts = natts;
pfree(attnums);
pfree(history_attnums);
}
/*
* Insert a row into the history relation.
*
* tuple: a row to insert
* relation: versioned relation
* history_relation_name: qualified name of the history relation
*/
static void
insert_history_row(HeapTuple tuple,
Relation relation,
const char *history_relation_name,
const char *period_attname)
{
RangeVar *relrv;
Relation history_relation;
VersioningHashEntry *hash_entry;
bool found;
TupleDesc tupdesc;
int ret;
int natts;
/* Open the history relation and obtain AccessShareLock on it. */
relrv = makeRangeVarFromNameList(stringToQualifiedNameList(history_relation_name));
history_relation = heap_openrv(relrv, AccessShareLock);
/* Look up the cached data for the versioned relation OID. */
hash_entry = lookup_versioning_hash_entry(RelationGetRelid(relation),
&found);
tupdesc = RelationGetDescr(relation);
if (found)
{
TupleDesc history_tupdesc;
history_tupdesc = RelationGetDescr(history_relation);
/*
* Check that the cached data is still valid.
*
* If natts is -1, then fill_versioning_hash_entry failed and the
* cached data is invalid.
*
* If the trigger definition changes, then the cached history relation
* OID may differs compared to the current one.
*
* Then check that the structure of the versioned table and the history
* table is intact by comparing the cached TupleDesc with the current
* one.
*/
if (hash_entry->natts == -1 ||
RelationGetRelid(history_relation) != hash_entry->history_relid ||
!equalTupleDescs(tupdesc, hash_entry->tupdesc) ||
!equalTupleDescs(history_tupdesc, hash_entry->history_tupdesc))
{
/* Mark the entry invalid. */
hash_entry->natts = -1;
/* If the cached data structure is invalid, free it's fields. */
if (hash_entry->tupdesc != NULL)
{
FreeTupleDesc(hash_entry->tupdesc);
hash_entry->tupdesc = NULL;
}
if (hash_entry->history_tupdesc != NULL)
{
FreeTupleDesc(hash_entry->history_tupdesc);
hash_entry->history_tupdesc = NULL;
}
if (hash_entry->attnums != NULL)
{
pfree(hash_entry->attnums);
hash_entry->attnums = NULL;
}
if (hash_entry->insert_history_plan != NULL)
{
if ((ret = SPI_freeplan(hash_entry->insert_history_plan)) != 0)
elog(ERROR, "SPI_freeplan returned %d", ret);
hash_entry->insert_history_plan = NULL;
}
/* Make to refill the cached data entry. */
found = false;
}
}
if ((ret = SPI_connect()) != SPI_OK_CONNECT)
elog(ERROR, "SPI_connect returned %d", ret);
/*
* If there is no cached data or it is invalid, fill the cached data
* structure.
*/
if (!found)
{
fill_versioning_hash_entry(hash_entry, relation, history_relation,
tupdesc, period_attname);
}
natts = hash_entry->natts;
/* Execute the plan. */
if (natts != 0)
{
Datum *values;
char *nulls;
int *attnums;
SPIPlanPtr plan;
int i;
values = palloc(natts * sizeof(Datum));
nulls = palloc(natts * sizeof(char));
attnums = hash_entry->attnums;
plan = hash_entry->insert_history_plan;
for (i = 0; i < natts; ++i)
{
bool isnull;
values[i] = SPI_getbinval(tuple, tupdesc, attnums[i], &isnull);
nulls[i] = isnull ? 'n' : ' ';
}
if ((ret = SPI_execp(plan, values, nulls, 0)) != SPI_OK_INSERT)
elog(ERROR, "SPI_execp returned %d", ret);
pfree(values);
pfree(nulls);
}
/* Close the history relation. */
relation_close(history_relation, AccessShareLock);
if ((ret = SPI_finish()) != SPI_OK_FINISH)
elog(ERROR, "SPI_finish returned %d", ret);
}
/*
* Deconstruct a range value of the system period attribute.
*
* If the value is null or is bounded on it's high side, an error is thrown.
*/
static void
deserialize_system_period(HeapTuple tuple,
Relation relation,
int period_attnum,
const char *period_attname,
TypeCacheEntry *typcache,
RangeBound *lower,
RangeBound *upper)
{
bool isnull;
Datum datum;
RangeType *system_period;
bool empty;
datum = SPI_getbinval(tuple, RelationGetDescr(relation), period_attnum,
&isnull);
if (isnull)
ereport(ERROR,
(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
errmsg("system period column \"%s\" of relation \"%s\" must not be null",
period_attname,
RelationGetRelationName(relation))));
system_period = DatumGetRangeType(datum);
range_deserialize(typcache, system_period, lower, upper, &empty);
if (empty || !upper->infinite)
ereport(ERROR,
(errcode(ERRCODE_DATA_EXCEPTION),
errmsg("system period column \"%s\" of relation \"%s\" contains invalid value",
period_attname,
RelationGetRelationName(relation)),
errdetail("valid ranges must be non-empty and unbounded on the high side")));
}
/*
* Look up "integer_datetimes" configuration option.
*/
static void
lookup_integer_datetimes()
{
const char *value;
value = GetConfigOption("integer_datetimes", false, true);
integer_datetimes = (strcmp(value, "on") == 0);
integer_datetimes_set = true;
}
/*
* Add a minimal time interval to the specified timestamp. The returned value
* is always not equal to this timestamp.
*/
static TimestampTz
next_timestamp(TimestampTz timestamp)
{
if (!integer_datetimes_set)
lookup_integer_datetimes();
/* If Timestamp is int64, add 1 microsecond. */
if (integer_datetimes)
return (TimestampTz) ((int64) timestamp + 1);
else
{
float8 ts;
float8 next;
/*
* If Timestamp is double, try adding 1 microsecond. If microsecond
* precision is not available for this value, return the next
* representable floating-point number.
*/
ts = (float8) timestamp;
next = ts + 1E-06;
if (next != ts)
return (TimestampTz) next;
return (TimestampTz) nextafter(ts, DBL_MAX);
}
}
/*
* Check that the upper bound is greater than the lower bound. If it is not
* the case and adjust argument of the trigger is set to false, an exception
* is thrown. If adjust argument is set to true, then the upper bound is set
* to the lower bound plus delta.
*/
static void
adjust_system_period(TypeCacheEntry *typcache,
RangeBound *lower,
RangeBound *upper,
const char *adjust_argument,
Relation relation)
{
if (range_cmp_bounds(typcache, lower, upper) >= 0)
{
TimestampTz next_ts;
if (!parse_adjust_argument(adjust_argument))
ereport(ERROR,
(errcode(ERRCODE_DATA_EXCEPTION),
errmsg("system period value of relation \"%s\" cannot be set to a valid period because a row that is attempted to modify was also modified by another transaction",
RelationGetRelationName(relation)),
errdetail("the start time of system period is %s but the start time of the current transaction is %s",
lower->infinite ? "-infinity" : timestamptz_to_str(DatumGetTimestampTz(lower->val)),
timestamptz_to_str(DatumGetTimestampTz(upper->val))),
errhint("retry the statement or set \"adjust\" parameter of \"versioning\" function to true")));
ereport(WARNING,
(errcode(ERRCODE_WARNING_SYSTEM_PERIOD_ADJUSTED),
errmsg("system period value of relation \"%s\" was adjusted",
RelationGetRelationName(relation))));
next_ts = next_timestamp(DatumGetTimestampTz(lower->val));
upper->val = TimestampTzGetDatum(next_ts);
}
}
/*
* Check if the tuple was inserted or updated in the current transaction.
*/
static bool
modified_in_current_transaction(HeapTuple tuple)
{
TransactionId oldxmin;
oldxmin = HeapTupleHeaderGetXmin(tuple->t_data);
return TransactionIdIsCurrentTransactionId(oldxmin);
}
/*
* Tuple modification wrapper around SPI_modifytuple for PG<10
* and heap_modify_tuple_by_cols for PG 10
*/
static HeapTuple
modify_tuple(Relation rel, HeapTuple tuple, int period_attnum, RangeType *range)
{
int colnum[1] = { period_attnum };
Datum values[1] = { RangeTypeGetDatum(range) };
#if PG_VERSION_NUM >= 100000
bool nulls[1] = { false };
return heap_modify_tuple_by_cols(tuple, RelationGetDescr(rel), 1, colnum, values, nulls);
#else
char nulls[1] = { ' ' };
return SPI_modifytuple(rel, tuple, 1, colnum, values, nulls);
#endif
}
/*
* Set system period attribute value of the current row to
* "[system_time, )".
*/
static Datum
versioning_insert(TriggerData *trigdata,
TypeCacheEntry *typcache,
int period_attnum)
{
RangeBound lower;
RangeBound upper;
RangeType *range;
/* Construct a period for the current row. */
lower.val = TimestampTzGetDatum(get_system_time());
lower.infinite = false;
lower.inclusive = true;
lower.lower = true;
upper.infinite = true;
upper.inclusive = false;
upper.lower = false;
range = make_range(typcache, &lower, &upper, false);
return PointerGetDatum(modify_tuple(trigdata->tg_relation, trigdata->tg_trigtuple, period_attnum, range));
}
/*
* Set system period attribute value of the current row to
* "[system_time, )", insert the original row into the history table
* with the system period attribute value "[lower, system_time)".
*
* If lower is greater than or equals to system_time, adjust argument
* determines whether timestamps adjustment are made or transaction should
* fail.
*
* When a transaction makes multiple changes to a row, a history row is
* generated only once.
*/
static Datum
versioning_update(TriggerData *trigdata,
TypeCacheEntry *typcache,
int period_attnum,
const char *period_attname,
const char *history_relation_argument,
const char *adjust_argument)
{
HeapTuple tuple;
Relation relation;
RangeBound lower;
RangeBound upper;
RangeType *range;
HeapTuple history_tuple;
tuple = trigdata->tg_trigtuple;
/* Ignore tuples modified in this transaction. */
if (modified_in_current_transaction(tuple))
return PointerGetDatum(trigdata->tg_newtuple);
relation = trigdata->tg_relation;
deserialize_system_period(tuple, relation, period_attnum, period_attname,
typcache, &lower, &upper);
/* Construct a period for the history row. */
upper.val = TimestampTzGetDatum(get_system_time());
upper.infinite = false;
upper.inclusive = false;
/* Adjust if needed. */
adjust_system_period(typcache, &lower, &upper, adjust_argument, relation);
range = make_range(typcache, &lower, &upper, false);
history_tuple = modify_tuple(relation, tuple, period_attnum, range);
insert_history_row(history_tuple, relation, history_relation_argument,
period_attname);
/* Construct a period for the current row. */
lower.val = upper.val;
lower.infinite = false;
lower.inclusive = true;
upper.infinite = true;
upper.inclusive = false;
range = make_range(typcache, &lower, &upper, false);
return PointerGetDatum(modify_tuple(relation, trigdata->tg_newtuple, period_attnum, range));
}
/*
* Insert the original row into the history table with the system period
* attribute value "[lower, system_time)".
*
* If lower is greater than or equals to system_time, adjust argument
* determines whether timestamps adjustment are made or transaction should
* fail.
*/
static Datum
versioning_delete(TriggerData *trigdata,
TypeCacheEntry *typcache,
int period_attnum,
const char *period_attname,
const char *history_relation_argument,
const char *adjust_argument)
{