Re: [POC] hash partitioning

Hi, Yugo.

Looks like a great feature! I'm going to take a closer look on your code
and write a feedback shortly. For now I can only tell that you forgot
to include some documentation in the patch.

I've added a corresponding entry to current commitfest [1]. Hope you
don't mind. If it's not too much trouble could you please register on a
commitfest site and add yourself to this entry as an author? I'm pretty
sure someone is using this information for writing release notes or
something like this.

[1] https://commitfest.postgresql.org/13/1059/

On Tue, Feb 28, 2017 at 11:33:13PM +0900, Yugo Nagata wrote:
> Hi all,
>
> Now we have a declarative partitioning, but hash partitioning is not
> implemented yet. Attached is a POC patch to add the hash partitioning
> feature. I know we will need more discussions about the syntax and other
> specifications before going ahead the project, but I think this runnable
> code might help to discuss what and how we implement this.
>
> * Description
>
> In this patch, the hash partitioning implementation is basically based
> on the list partitioning mechanism. However, partition bounds cannot be
> specified explicitly, but this is used internally as hash partition
> index, which is calculated when a partition is created or attached.
>
> The tentative syntax to create a partitioned table is as bellow;
>
> CREATE TABLE h (i int) PARTITION BY HASH(i) PARTITIONS 3 USING hashint4;
>
> The number of partitions is specified by PARTITIONS, which is currently
> constant and cannot be changed, but I think this is needed to be changed in
> some manner. A hash function is specified by USING. Maybe, specifying hash
> function may be ommitted, and in this case, a default hash function
> corresponding to key type will be used.
>
> A partition table can be create as bellow;
>
> CREATE TABLE h1 PARTITION OF h;
> CREATE TABLE h2 PARTITION OF h;
> CREATE TABLE h3 PARTITION OF h;
>
> FOR VALUES clause cannot be used, and the partition bound is
> calclulated automatically as partition index of single integer value.
>
> When trying create partitions more than the number specified
> by PARTITIONS, it gets an error.
>
> postgres=# create table h4 partition of h;
> ERROR: cannot create hash partition more than 3 for h
>
> An inserted record is stored in a partition whose index equals
> abs(hashfunc(key)) % <number_of_partitions>. In the above
> example, this is abs(hashint4(i))%3.
>
> postgres=# insert into h (select generate_series(0,20));
> INSERT 0 21
>
> postgres=# select *,tableoid::regclass from h;
> i | tableoid
> ----+----------
> 0 | h1
> 1 | h1
> 2 | h1
> 4 | h1
> 8 | h1
> 10 | h1
> 11 | h1
> 14 | h1
> 15 | h1
> 17 | h1
> 20 | h1
> 5 | h2
> 12 | h2
> 13 | h2
> 16 | h2
> 19 | h2
> 3 | h3
> 6 | h3
> 7 | h3
> 9 | h3
> 18 | h3
> (21 rows)
>
> * Todo / discussions
>
> In this patch, we cannot change the number of partitions specified
> by PARTITIONS. I we can change this, the partitioning rule
> (<partition index> = abs(hashfunc(key)) % <number_of_partitions>)
> is also changed and then we need reallocatiing records between
> partitions.
>
> In this patch, user can specify a hash function USING. However,
> we migth need default hash functions which are useful and
> proper for hash partitioning.
>
> Currently, even when we issue SELECT query with a condition,
> postgres looks into all partitions regardless of each partition's
> constraint, because this is complicated such like "abs(hashint4(i))%3 = 0".
>
> postgres=# explain select * from h where i = 10;
> QUERY PLAN
> ----------------------------------------------------------
> Append (cost=0.00..125.62 rows=40 width=4)
> -> Seq Scan on h (cost=0.00..0.00 rows=1 width=4)
> Filter: (i = 10)
> -> Seq Scan on h1 (cost=0.00..41.88 rows=13 width=4)
> Filter: (i = 10)
> -> Seq Scan on h2 (cost=0.00..41.88 rows=13 width=4)
> Filter: (i = 10)
> -> Seq Scan on h3 (cost=0.00..41.88 rows=13 width=4)
> Filter: (i = 10)
> (9 rows)
>
> However, if we modify a condition into a same expression
> as the partitions constraint, postgres can exclude unrelated
> table from search targets. So, we might avoid the problem
> by converting the qual properly before calling predicate_refuted_by().
>
> postgres=# explain select * from h where abs(hashint4(i))%3 = abs(hashint4(10))%3;
> QUERY PLAN
> ----------------------------------------------------------
> Append (cost=0.00..61.00 rows=14 width=4)
> -> Seq Scan on h (cost=0.00..0.00 rows=1 width=4)
> Filter: ((abs(hashint4(i)) % 3) = 2)
> -> Seq Scan on h3 (cost=0.00..61.00 rows=13 width=4)
> Filter: ((abs(hashint4(i)) % 3) = 2)
> (5 rows)
>
> Best regards,
> Yugo Nagata
>
> --
> Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>

> diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
> index 41c0056..3820920 100644
> --- a/src/backend/catalog/heap.c
> +++ b/src/backend/catalog/heap.c
> @@ -3074,7 +3074,7 @@ StorePartitionKey(Relation rel,
> AttrNumber *partattrs,
> List *partexprs,
> Oid *partopclass,
> - Oid *partcollation)
> + Oid *partcollation, int16 partnparts, Oid hashfunc)
> {
> int i;
> int2vector *partattrs_vec;
> @@ -3121,6 +3121,8 @@ StorePartitionKey(Relation rel,
> values[Anum_pg_partitioned_table_partrelid - 1] = ObjectIdGetDatum(RelationGetRelid(rel));
> values[Anum_pg_partitioned_table_partstrat - 1] = CharGetDatum(strategy);
> values[Anum_pg_partitioned_table_partnatts - 1] = Int16GetDatum(partnatts);
> + values[Anum_pg_partitioned_table_partnparts - 1] = Int16GetDatum(partnparts);
> + values[Anum_pg_partitioned_table_parthashfunc - 1] = ObjectIdGetDatum(hashfunc);
> values[Anum_pg_partitioned_table_partattrs - 1] = PointerGetDatum(partattrs_vec);
> values[Anum_pg_partitioned_table_partclass - 1] = PointerGetDatum(partopclass_vec);
> values[Anum_pg_partitioned_table_partcollation - 1] = PointerGetDatum(partcollation_vec);
> diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
> index 4bcef58..24e69c6 100644
> --- a/src/backend/catalog/partition.c
> +++ b/src/backend/catalog/partition.c
> @@ -36,6 +36,8 @@
> #include "optimizer/clauses.h"
> #include "optimizer/planmain.h"
> #include "optimizer/var.h"
> +#include "parser/parse_func.h"
> +#include "parser/parse_oper.h"
> #include "rewrite/rewriteManip.h"
> #include "storage/lmgr.h"
> #include "utils/array.h"
> @@ -120,6 +122,7 @@ static int32 qsort_partition_rbound_cmp(const void *a, const void *b,
>
> static List *get_qual_for_list(PartitionKey key, PartitionBoundSpec *spec);
> static List *get_qual_for_range(PartitionKey key, PartitionBoundSpec *spec);
> +static List *get_qual_for_hash(PartitionKey key, PartitionBoundSpec *spec);
> static Oid get_partition_operator(PartitionKey key, int col,
> StrategyNumber strategy, bool *need_relabel);
> static List *generate_partition_qual(Relation rel);
> @@ -236,7 +239,8 @@ RelationBuildPartitionDesc(Relation rel)
> oids[i++] = lfirst_oid(cell);
>
> /* Convert from node to the internal representation */
> - if (key->strategy == PARTITION_STRATEGY_LIST)
> + if (key->strategy == PARTITION_STRATEGY_LIST ||
> + key->strategy == PARTITION_STRATEGY_HASH)
> {
> List *non_null_values = NIL;
>
> @@ -251,7 +255,7 @@ RelationBuildPartitionDesc(Relation rel)
> ListCell *c;
> PartitionBoundSpec *spec = lfirst(cell);
>
> - if (spec->strategy != PARTITION_STRATEGY_LIST)
> + if (spec->strategy != key->strategy)
> elog(ERROR, "invalid strategy in partition bound spec");
>
> foreach(c, spec->listdatums)
> @@ -464,6 +468,7 @@ RelationBuildPartitionDesc(Relation rel)
> switch (key->strategy)
> {
> case PARTITION_STRATEGY_LIST:
> + case PARTITION_STRATEGY_HASH:
> {
> boundinfo->has_null = found_null;
> boundinfo->indexes = (int *) palloc(ndatums * sizeof(int));
> @@ -829,6 +834,18 @@ check_new_partition_bound(char *relname, Relation parent, Node *bound)
> break;
> }
>
> + case PARTITION_STRATEGY_HASH:
> + {
> + Assert(spec->strategy == PARTITION_STRATEGY_HASH);
> +
> + if (partdesc->nparts + 1 > key->partnparts)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
> + errmsg("cannot create hash partition more than %d for %s",
> + key->partnparts, RelationGetRelationName(parent))));
> + break;
> + }
> +
> default:
> elog(ERROR, "unexpected partition strategy: %d",
> (int) key->strategy);
> @@ -916,6 +933,11 @@ get_qual_from_partbound(Relation rel, Relation parent, Node *bound)
> my_qual = get_qual_for_range(key, spec);
> break;
>
> + case PARTITION_STRATEGY_HASH:
> + Assert(spec->strategy == PARTITION_STRATEGY_LIST);
> + my_qual = get_qual_for_hash(key, spec);
> + break;
> +
> default:
> elog(ERROR, "unexpected partition strategy: %d",
> (int) key->strategy);
> @@ -1146,6 +1168,84 @@ RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
> return pd;
> }
>
> +/*
> + * convert_expr_for_hash
> + *
> + * Converts a expr for a hash partition's constraint.
> + * expr is converted into 'abs(hashfunc(expr)) % npart".
> + *
> + * npart: number of partitions
> + * hashfunc: OID of hash function
> + */
> +Expr *
> +convert_expr_for_hash(Expr *expr, int npart, Oid hashfunc)
> +{
> + FuncExpr *func,
> + *abs;
> + Expr *modexpr;
> + Oid modoid;
> + Oid int4oid[1] = {INT4OID};
> +
> + ParseState *pstate = make_parsestate(NULL);
> + Value *val_npart = makeInteger(npart);
> + Node *const_npart = (Node *) make_const(pstate, val_npart, -1);
> +
> + /* hash function */
> + func = makeFuncExpr(hashfunc,
> + INT4OID,
> + list_make1(expr),
> + 0,
> + 0,
> + COERCE_EXPLICIT_CALL);
> +
> + /* Abs */
> + abs = makeFuncExpr(LookupFuncName(list_make1(makeString("abs")), 1, int4oid, false),
> + INT4OID,
> + list_make1(func),
> + 0,
> + 0,
> + COERCE_EXPLICIT_CALL);
> +
> + /* modulo by npart */
> + modoid = LookupOperName(pstate, list_make1(makeString("%")), INT4OID, INT4OID, false, -1);
> + modexpr = make_opclause(modoid, INT4OID, false, (Expr*)abs, (Expr*)const_npart, 0, 0);
> +
> + return modexpr;
> +}
> +
> +
> +/*
> + * get_next_hash_partition_index
> + *
> + * Returns the minimal index which is not used for hash partition.
> + */
> +int
> +get_next_hash_partition_index(Relation parent)
> +{
> + PartitionKey key = RelationGetPartitionKey(parent);
> + PartitionDesc partdesc = RelationGetPartitionDesc(parent);
> +
> + int i;
> + bool *used = palloc0(sizeof(int) * key->partnparts);
> +
> + /* mark used for existing partition indexs */
> + for (i = 0; i < partdesc->boundinfo->ndatums; i++)
> + {
> + Datum* datum = partdesc->boundinfo->datums[i];
> + int idx = DatumGetInt16(datum[0]);
> +
> + if (!used[idx])
> + used[idx] = true;
> + }
> +
> + /* find the minimal unused index */
> + for (i = 0; i < key->partnparts; i++)
> + if (!used[i])
> + break;
> +
> + return i;
> +}
> +
> /* Module-local functions */
>
> /*
> @@ -1467,6 +1567,43 @@ get_qual_for_range(PartitionKey key, PartitionBoundSpec *spec)
> }
>
> /*
> + * get_qual_for_hash
> + *
> + * Returns a list of expressions to use as a hash partition's constraint.
> + */
> +static List *
> +get_qual_for_hash(PartitionKey key, PartitionBoundSpec *spec)
> +{
> + List *result;
> + Expr *keyCol;
> + Expr *expr;
> + Expr *opexpr;
> + Oid operoid;
> + ParseState *pstate = make_parsestate(NULL);
> +
> + /* Left operand */
> + if (key->partattrs[0] != 0)
> + keyCol = (Expr *) makeVar(1,
> + key->partattrs[0],
> + key->parttypid[0],
> + key->parttypmod[0],
> + key->parttypcoll[0],
> + 0);
> + else
> + keyCol = (Expr *) copyObject(linitial(key->partexprs));
> +
> + expr = convert_expr_for_hash(keyCol, key->partnparts, key->parthashfunc);
> +
> + /* equals the listdaums value */
> + operoid = LookupOperName(pstate, list_make1(makeString("=")), INT4OID, INT4OID, false, -1);
> + opexpr = make_opclause(operoid, BOOLOID, false, expr, linitial(spec->listdatums), 0, 0);
> +
> + result = list_make1(opexpr);
> +
> + return result;
> +}
> +
> +/*
> * get_partition_operator
> *
> * Return oid of the operator of given strategy for a given partition key
> @@ -1730,6 +1867,11 @@ get_partition_for_tuple(PartitionDispatch *pd,
> (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
> errmsg("range partition key of row contains null")));
> }
> + else if (key->strategy == PARTITION_STRATEGY_HASH)
> + {
> + values[0] = OidFunctionCall1(key->parthashfunc, values[0]);
> + values[0] = Int16GetDatum(Abs(DatumGetInt16(values[0])) % key->partnparts);
> + }
>
> if (partdesc->boundinfo->has_null && isnull[0])
> /* Tuple maps to the null-accepting list partition */
> @@ -1744,6 +1886,7 @@ get_partition_for_tuple(PartitionDispatch *pd,
> switch (key->strategy)
> {
> case PARTITION_STRATEGY_LIST:
> + case PARTITION_STRATEGY_HASH:
> if (cur_offset >= 0 && equal)
> cur_index = partdesc->boundinfo->indexes[cur_offset];
> else
> @@ -1968,6 +2111,7 @@ partition_bound_cmp(PartitionKey key, PartitionBoundInfo boundinfo,
> switch (key->strategy)
> {
> case PARTITION_STRATEGY_LIST:
> + case PARTITION_STRATEGY_HASH:
> cmpval = DatumGetInt32(FunctionCall2Coll(&key->partsupfunc[0],
> key->partcollation[0],
> bound_datums[0],
> diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
> index 3cea220..5a28cc0 100644
> --- a/src/backend/commands/tablecmds.c
> +++ b/src/backend/commands/tablecmds.c
> @@ -41,6 +41,7 @@
> #include "catalog/pg_inherits_fn.h"
> #include "catalog/pg_namespace.h"
> #include "catalog/pg_opclass.h"
> +#include "catalog/pg_proc.h"
> #include "catalog/pg_tablespace.h"
> #include "catalog/pg_trigger.h"
> #include "catalog/pg_type.h"
> @@ -77,6 +78,7 @@
> #include "parser/parse_oper.h"
> #include "parser/parse_relation.h"
> #include "parser/parse_type.h"
> +#include "parser/parse_func.h"
> #include "parser/parse_utilcmd.h"
> #include "parser/parser.h"
> #include "pgstat.h"
> @@ -450,7 +452,7 @@ static void RangeVarCallbackForAlterRelation(const RangeVar *rv, Oid relid,
> Oid oldrelid, void *arg);
> static bool is_partition_attr(Relation rel, AttrNumber attnum, bool *used_in_expr);
> static PartitionSpec *transformPartitionSpec(Relation rel, PartitionSpec *partspec, char *strategy);
> -static void ComputePartitionAttrs(Relation rel, List *partParams, AttrNumber *partattrs,
> +static void ComputePartitionAttrs(Relation rel, List *partParams, AttrNumber *partattrs, Oid *partatttypes,
> List **partexprs, Oid *partopclass, Oid *partcollation);
> static void CreateInheritance(Relation child_rel, Relation parent_rel);
> static void RemoveInheritance(Relation child_rel, Relation parent_rel);
> @@ -799,8 +801,10 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
> AttrNumber partattrs[PARTITION_MAX_KEYS];
> Oid partopclass[PARTITION_MAX_KEYS];
> Oid partcollation[PARTITION_MAX_KEYS];
> + Oid partatttypes[PARTITION_MAX_KEYS];
> List *partexprs = NIL;
> List *cmds = NIL;
> + Oid hashfuncOid = InvalidOid;
>
> /*
> * We need to transform the raw parsetrees corresponding to partition
> @@ -811,15 +815,40 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
> stmt->partspec = transformPartitionSpec(rel, stmt->partspec,
> &strategy);
> ComputePartitionAttrs(rel, stmt->partspec->partParams,
> - partattrs, &partexprs, partopclass,
> + partattrs, partatttypes, &partexprs, partopclass,
> partcollation);
>
> partnatts = list_length(stmt->partspec->partParams);
> +
> + if (strategy == PARTITION_STRATEGY_HASH)
> + {
> + Oid funcrettype;
> +
> + if (partnatts != 1)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("number of partition key must be 1 for hash partition")));
> +
> + hashfuncOid = LookupFuncName(stmt->partspec->hashfunc, 1, partatttypes, false);
> + funcrettype = get_func_rettype(hashfuncOid);
> + if (funcrettype != INT4OID)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("hash function for partitioning must return integer")));
> +
> + if (func_volatile(hashfuncOid) != PROVOLATILE_IMMUTABLE)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("hash function for partitioning must be marked IMMUTABLE")));
> +
> + }
> +
> StorePartitionKey(rel, strategy, partnatts, partattrs, partexprs,
> - partopclass, partcollation);
> + partopclass, partcollation, stmt->partspec->partnparts, hashfuncOid);
>
> - /* Force key columns to be NOT NULL when using range partitioning */
> - if (strategy == PARTITION_STRATEGY_RANGE)
> + /* Force key columns to be NOT NULL when using range or hash partitioning */
> + if (strategy == PARTITION_STRATEGY_RANGE ||
> + strategy == PARTITION_STRATEGY_HASH)
> {
> for (i = 0; i < partnatts; i++)
> {
> @@ -12783,18 +12812,51 @@ transformPartitionSpec(Relation rel, PartitionSpec *partspec, char *strategy)
> newspec->strategy = partspec->strategy;
> newspec->location = partspec->location;
> newspec->partParams = NIL;
> + newspec->partnparts = partspec->partnparts;
> + newspec->hashfunc = partspec->hashfunc;
>
> /* Parse partitioning strategy name */
> if (!pg_strcasecmp(partspec->strategy, "list"))
> *strategy = PARTITION_STRATEGY_LIST;
> else if (!pg_strcasecmp(partspec->strategy, "range"))
> *strategy = PARTITION_STRATEGY_RANGE;
> + else if (!pg_strcasecmp(partspec->strategy, "hash"))
> + *strategy = PARTITION_STRATEGY_HASH;
> else
> ereport(ERROR,
> (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> errmsg("unrecognized partitioning strategy \"%s\"",
> partspec->strategy)));
>
> + if (*strategy == PARTITION_STRATEGY_HASH)
> + {
> + if (partspec->partnparts < 0)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("number of partitions must be specified for hash partition")));
> + else if (partspec->partnparts == 0)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("number of partitions must be greater than 0")));
> +
> + if (list_length(partspec->hashfunc) == 0)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("hash function must be specified for hash partition")));
> + }
> + else
> + {
> + if (partspec->partnparts >= 0)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("number of partitions can be specified only for hash partition")));
> +
> + if (list_length(partspec->hashfunc) > 0)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
> + errmsg("hash function can be specified only for hash partition")));
> + }
> +
> /*
> * Create a dummy ParseState and insert the target relation as its sole
> * rangetable entry. We need a ParseState for transformExpr.
> @@ -12843,7 +12905,7 @@ transformPartitionSpec(Relation rel, PartitionSpec *partspec, char *strategy)
> * Compute per-partition-column information from a list of PartitionElem's
> */
> static void
> -ComputePartitionAttrs(Relation rel, List *partParams, AttrNumber *partattrs,
> +ComputePartitionAttrs(Relation rel, List *partParams, AttrNumber *partattrs, Oid *partatttypes,
> List **partexprs, Oid *partopclass, Oid *partcollation)
> {
> int attn;
> @@ -13010,6 +13072,7 @@ ComputePartitionAttrs(Relation rel, List *partParams, AttrNumber *partattrs,
> "btree",
> BTREE_AM_OID);
>
> + partatttypes[attn] = atttype;
> attn++;
> }
> }
> diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
> index 05d8538..f4febc9 100644
> --- a/src/backend/nodes/copyfuncs.c
> +++ b/src/backend/nodes/copyfuncs.c
> @@ -4232,6 +4232,8 @@ _copyPartitionSpec(const PartitionSpec *from)
>
> COPY_STRING_FIELD(strategy);
> COPY_NODE_FIELD(partParams);
> + COPY_SCALAR_FIELD(partnparts);
> + COPY_NODE_FIELD(hashfunc);
> COPY_LOCATION_FIELD(location);
>
> return newnode;
> diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
> index d595cd7..d589eac 100644
> --- a/src/backend/nodes/equalfuncs.c
> +++ b/src/backend/nodes/equalfuncs.c
> @@ -2725,6 +2725,8 @@ _equalPartitionSpec(const PartitionSpec *a, const PartitionSpec *b)
> {
> COMPARE_STRING_FIELD(strategy);
> COMPARE_NODE_FIELD(partParams);
> + COMPARE_SCALAR_FIELD(partnparts);
> + COMPARE_NODE_FIELD(hashfunc);
> COMPARE_LOCATION_FIELD(location);
>
> return true;
> diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
> index b3802b4..d6db80e 100644
> --- a/src/backend/nodes/outfuncs.c
> +++ b/src/backend/nodes/outfuncs.c
> @@ -3318,6 +3318,8 @@ _outPartitionSpec(StringInfo str, const PartitionSpec *node)
>
> WRITE_STRING_FIELD(strategy);
> WRITE_NODE_FIELD(partParams);
> + WRITE_INT_FIELD(partnparts);
> + WRITE_NODE_FIELD(hashfunc);
> WRITE_LOCATION_FIELD(location);
> }
>
> diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
> index e833b2e..b67140d 100644
> --- a/src/backend/parser/gram.y
> +++ b/src/backend/parser/gram.y
> @@ -574,6 +574,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
> %type <list> partbound_datum_list
> %type <partrange_datum> PartitionRangeDatum
> %type <list> range_datum_list
> +%type <ival> hash_partitions
> +%type <list> hash_function
>
> /*
> * Non-keyword token types. These are hard-wired into the "flex" lexer.
> @@ -627,7 +629,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
>
> GLOBAL GRANT GRANTED GREATEST GROUP_P GROUPING
>
> - HANDLER HAVING HEADER_P HOLD HOUR_P
> + HANDLER HASH HAVING HEADER_P HOLD HOUR_P
>
> IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P
> INCLUDING INCREMENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
> @@ -651,7 +653,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
> OBJECT_P OF OFF OFFSET OIDS OLD ON ONLY OPERATOR OPTION OPTIONS OR
> ORDER ORDINALITY OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
>
> - PARALLEL PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POLICY
> + PARALLEL PARSER PARTIAL PARTITION PARTITIONS PASSING PASSWORD PLACING PLANS POLICY
> POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
> PRIOR PRIVILEGES PROCEDURAL PROCEDURE PROGRAM PUBLICATION
>
> @@ -2587,6 +2589,16 @@ ForValues:
>
> $$ = (Node *) n;
> }
> +
> + /* a HASH partition */
> + | /*EMPTY*/
> + {
> + PartitionBoundSpec *n = makeNode(PartitionBoundSpec);
> +
> + n->strategy = PARTITION_STRATEGY_HASH;
> +
> + $$ = (Node *) n;
> + }
> ;
>
> partbound_datum:
> @@ -3666,7 +3678,7 @@ OptPartitionSpec: PartitionSpec { $$ = $1; }
> | /*EMPTY*/ { $$ = NULL; }
> ;
>
> -PartitionSpec: PARTITION BY part_strategy '(' part_params ')'
> +PartitionSpec: PARTITION BY part_strategy '(' part_params ')' hash_partitions hash_function
> {
> PartitionSpec *n = makeNode(PartitionSpec);
>
> @@ -3674,10 +3686,21 @@ PartitionSpec: PARTITION BY part_strategy '(' part_params ')'
> n->partParams = $5;
> n->location = @1;
>
> + n->partnparts = $7;
> + n->hashfunc = $8;
> +
> $$ = n;
> }
> ;
>
> +hash_partitions: PARTITIONS Iconst { $$ = $2; }
> + | /*EMPTY*/ { $$ = -1; }
> + ;
> +
> +hash_function: USING handler_name { $$ = $2; }
> + | /*EMPTY*/ { $$ = NULL; }
> + ;
> +
> part_strategy: IDENT { $$ = $1; }
> | unreserved_keyword { $$ = pstrdup($1); }
> ;
> @@ -14377,6 +14400,7 @@ unreserved_keyword:
> | GLOBAL
> | GRANTED
> | HANDLER
> + | HASH
> | HEADER_P
> | HOLD
> | HOUR_P
> @@ -14448,6 +14472,7 @@ unreserved_keyword:
> | PARSER
> | PARTIAL
> | PARTITION
> + | PARTITIONS
> | PASSING
> | PASSWORD
> | PLANS
> diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
> index ff2bab6..8e1be31 100644
> --- a/src/backend/parser/parse_utilcmd.c
> +++ b/src/backend/parser/parse_utilcmd.c
> @@ -40,6 +40,7 @@
> #include "catalog/pg_opclass.h"
> #include "catalog/pg_operator.h"
> #include "catalog/pg_type.h"
> +#include "catalog/partition.h"
> #include "commands/comment.h"
> #include "commands/defrem.h"
> #include "commands/tablecmds.h"
> @@ -3252,6 +3253,24 @@ transformPartitionBound(ParseState *pstate, Relation parent, Node *bound)
> ++i;
> }
> }
> + else if (strategy == PARTITION_STRATEGY_HASH)
> + {
> + Value *conval;
> + Node *value;
> + int index;
> +
> + if (spec->strategy != PARTITION_STRATEGY_HASH)
> + ereport(ERROR,
> + (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
> + errmsg("invalid bound specification for a hash partition")));
> +
> + index = get_next_hash_partition_index(parent);
> +
> + /* store the partition index as a listdatums value */
> + conval = makeInteger(index);
> + value = (Node *) make_const(pstate, conval, -1);
> + result_spec->listdatums = list_make1(value);
> + }
> else
> elog(ERROR, "unexpected partition strategy: %d", (int) strategy);
>
> diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
> index b27b77d..fab6eea 100644
> --- a/src/backend/utils/adt/ruleutils.c
> +++ b/src/backend/utils/adt/ruleutils.c
> @@ -1423,7 +1423,7 @@ pg_get_indexdef_worker(Oid indexrelid, int colno,
> *
> * Returns the partition key specification, ie, the following:
> *
> - * PARTITION BY { RANGE | LIST } (column opt_collation opt_opclass [, ...])
> + * PARTITION BY { RANGE | LIST | HASH } (column opt_collation opt_opclass [, ...])
> */
> Datum
> pg_get_partkeydef(PG_FUNCTION_ARGS)
> @@ -1513,6 +1513,9 @@ pg_get_partkeydef_worker(Oid relid, int prettyFlags)
> case PARTITION_STRATEGY_RANGE:
> appendStringInfo(&buf, "RANGE");
> break;
> + case PARTITION_STRATEGY_HASH:
> + appendStringInfo(&buf, "HASH");
> + break;
> default:
> elog(ERROR, "unexpected partition strategy: %d",
> (int) form->partstrat);
> @@ -8520,6 +8523,9 @@ get_rule_expr(Node *node, deparse_context *context,
> appendStringInfoString(buf, ")");
> break;
>
> + case PARTITION_STRATEGY_HASH:
> + break;
> +
> default:
> elog(ERROR, "unrecognized partition strategy: %d",
> (int) spec->strategy);
> diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
> index 9001e20..829e4d2 100644
> --- a/src/backend/utils/cache/relcache.c
> +++ b/src/backend/utils/cache/relcache.c
> @@ -855,6 +855,9 @@ RelationBuildPartitionKey(Relation relation)
> key->strategy = form->partstrat;
> key->partnatts = form->partnatts;
>
> + key->partnparts = form->partnparts;
> + key->parthashfunc = form->parthashfunc;
> +
> /*
> * We can rely on the first variable-length attribute being mapped to the
> * relevant field of the catalog's C struct, because all previous
> @@ -999,6 +1002,9 @@ copy_partition_key(PartitionKey fromkey)
> newkey->strategy = fromkey->strategy;
> newkey->partnatts = n = fromkey->partnatts;
>
> + newkey->partnparts = fromkey->partnparts;
> + newkey->parthashfunc = fromkey->parthashfunc;
> +
> newkey->partattrs = (AttrNumber *) palloc(n * sizeof(AttrNumber));
> memcpy(newkey->partattrs, fromkey->partattrs, n * sizeof(AttrNumber));
>
> diff --git a/src/include/catalog/heap.h b/src/include/catalog/heap.h
> index 1187797..367e2f8 100644
> --- a/src/include/catalog/heap.h
> +++ b/src/include/catalog/heap.h
> @@ -141,7 +141,7 @@ extern void StorePartitionKey(Relation rel,
> AttrNumber *partattrs,
> List *partexprs,
> Oid *partopclass,
> - Oid *partcollation);
> + Oid *partcollation, int16 partnparts, Oid hashfunc);
> extern void RemovePartitionKeyByRelId(Oid relid);
> extern void StorePartitionBound(Relation rel, Relation parent, Node *bound);
>
> diff --git a/src/include/catalog/partition.h b/src/include/catalog/partition.h
> index b195d1a..80f4b0e 100644
> --- a/src/include/catalog/partition.h
> +++ b/src/include/catalog/partition.h
> @@ -89,4 +89,6 @@ extern int get_partition_for_tuple(PartitionDispatch *pd,
> TupleTableSlot *slot,
> EState *estate,
> Oid *failed_at);
> +extern Expr *convert_expr_for_hash(Expr *expr, int npart, Oid hashfunc);
> +extern int get_next_hash_partition_index(Relation parent);
> #endif /* PARTITION_H */
> diff --git a/src/include/catalog/pg_partitioned_table.h b/src/include/catalog/pg_partitioned_table.h
> index bdff36a..69e509c 100644
> --- a/src/include/catalog/pg_partitioned_table.h
> +++ b/src/include/catalog/pg_partitioned_table.h
> @@ -33,6 +33,9 @@ CATALOG(pg_partitioned_table,3350) BKI_WITHOUT_OIDS
> char partstrat; /* partitioning strategy */
> int16 partnatts; /* number of partition key columns */
>
> + int16 partnparts;
> + Oid parthashfunc;
> +
> /*
> * variable-length fields start here, but we allow direct access to
> * partattrs via the C struct. That's because the first variable-length
> @@ -49,6 +52,8 @@ CATALOG(pg_partitioned_table,3350) BKI_WITHOUT_OIDS
> pg_node_tree partexprs; /* list of expressions in the partition key;
> * one item for each zero entry in partattrs[] */
> #endif
> +
> +
> } FormData_pg_partitioned_table;
>
> /* ----------------
> @@ -62,13 +67,15 @@ typedef FormData_pg_partitioned_table *Form_pg_partitioned_table;
> * compiler constants for pg_partitioned_table
> * ----------------
> */
> -#define Natts_pg_partitioned_table 7
> +#define Natts_pg_partitioned_table 9
> #define Anum_pg_partitioned_table_partrelid 1
> #define Anum_pg_partitioned_table_partstrat 2
> #define Anum_pg_partitioned_table_partnatts 3
> -#define Anum_pg_partitioned_table_partattrs 4
> -#define Anum_pg_partitioned_table_partclass 5
> -#define Anum_pg_partitioned_table_partcollation 6
> -#define Anum_pg_partitioned_table_partexprs 7
> +#define Anum_pg_partitioned_table_partnparts 4
> +#define Anum_pg_partitioned_table_parthashfunc 5
> +#define Anum_pg_partitioned_table_partattrs 6
> +#define Anum_pg_partitioned_table_partclass 7
> +#define Anum_pg_partitioned_table_partcollation 8
> +#define Anum_pg_partitioned_table_partexprs 9
>
> #endif /* PG_PARTITIONED_TABLE_H */
> diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
> index 5afc3eb..1c3474f 100644
> --- a/src/include/nodes/parsenodes.h
> +++ b/src/include/nodes/parsenodes.h
> @@ -730,11 +730,14 @@ typedef struct PartitionSpec
> NodeTag type;
> char *strategy; /* partitioning strategy ('list' or 'range') */
> List *partParams; /* List of PartitionElems */
> + int partnparts;
> + List *hashfunc;
> int location; /* token location, or -1 if unknown */
> } PartitionSpec;
>
> #define PARTITION_STRATEGY_LIST 'l'
> #define PARTITION_STRATEGY_RANGE 'r'
> +#define PARTITION_STRATEGY_HASH 'h'
>
> /*
> * PartitionBoundSpec - a partition bound specification
> diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
> index 985d650..0597939 100644
> --- a/src/include/parser/kwlist.h
> +++ b/src/include/parser/kwlist.h
> @@ -180,6 +180,7 @@ PG_KEYWORD("greatest", GREATEST, COL_NAME_KEYWORD)
> PG_KEYWORD("group", GROUP_P, RESERVED_KEYWORD)
> PG_KEYWORD("grouping", GROUPING, COL_NAME_KEYWORD)
> PG_KEYWORD("handler", HANDLER, UNRESERVED_KEYWORD)
> +PG_KEYWORD("hash", HASH, UNRESERVED_KEYWORD)
> PG_KEYWORD("having", HAVING, RESERVED_KEYWORD)
> PG_KEYWORD("header", HEADER_P, UNRESERVED_KEYWORD)
> PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD)
> @@ -291,6 +292,7 @@ PG_KEYWORD("parallel", PARALLEL, UNRESERVED_KEYWORD)
> PG_KEYWORD("parser", PARSER, UNRESERVED_KEYWORD)
> PG_KEYWORD("partial", PARTIAL, UNRESERVED_KEYWORD)
> PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD)
> +PG_KEYWORD("partitions", PARTITIONS, UNRESERVED_KEYWORD)
> PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD)
> PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD)
> PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD)
> diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
> index a617a7c..660adfb 100644
> --- a/src/include/utils/rel.h
> +++ b/src/include/utils/rel.h
> @@ -62,6 +62,9 @@ typedef struct PartitionKeyData
> Oid *partopcintype; /* OIDs of opclass declared input data types */
> FmgrInfo *partsupfunc; /* lookup info for support funcs */
>
> + int16 partnparts; /* number of hash partitions */
> + Oid parthashfunc; /* OID of hash function */
> +
> /* Partitioning collation per attribute */
> Oid *partcollation;
>

>
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--
Best regards,
Aleksander Alekseev