typedef struct AggState
{
  ScanState  ss;        /* its first field is NodeTag */
  List     *aggs;      /* all Aggref nodes in targetlist & quals */
  int      numaggs;    /* length of list (could be zero!) */
  int      numtrans;    /* number of pertrans items */
  AggStrategy aggstrategy;  /* strategy mode */
  AggSplit  aggsplit;    /* agg-splitting mode, see nodes.h */
  AggStatePerPhase phase;    /* pointer to current phase data */
  int      numphases;    /* number of phases (including phase 0) */
  int      current_phase;  /* current phase number */
  AggStatePerAgg peragg;    /* per-Aggref information */
  AggStatePerTrans pertrans;  /* per-Trans state information */
  ExprContext *hashcontext;  /* econtexts for long-lived data (hashtable) */
  ExprContext **aggcontexts;  /* econtexts for long-lived data (per GS) */
  ExprContext *tmpcontext;  /* econtext for input expressions */
#define FIELDNO_AGGSTATE_CURAGGCONTEXT 14
  ExprContext *curaggcontext; /* currently active aggcontext */
  AggStatePerAgg curperagg;  /* currently active aggregate, if any */
#define FIELDNO_AGGSTATE_CURPERTRANS 16
  AggStatePerTrans curpertrans;  /* currently active trans state, if any */
  bool    input_done;    /* indicates end of input */
  bool    agg_done;    /* indicates completion of Agg scan */
  int      projected_set;  /* The last projected grouping set */
#define FIELDNO_AGGSTATE_CURRENT_SET 20
  int      current_set;  /* The current grouping set being evaluated */
  Bitmapset  *grouped_cols;  /* grouped cols in current projection */
  List     *all_grouped_cols;  /* list of all grouped cols in DESC order */
  /* These fields are for grouping set phase data */
  int      maxsets;    /* The max number of sets in any phase */
  AggStatePerPhase phases;  /* array of all phases */
  Tuplesortstate *sort_in;  /* sorted input to phases > 1 */
  Tuplesortstate *sort_out;  /* input is copied here for next phase */
  TupleTableSlot *sort_slot;  /* slot for sort results */
  /* these fields are used in AGG_PLAIN and AGG_SORTED modes: */
  AggStatePerGroup *pergroups;  /* grouping set indexed array of per-group
                   * pointers */
  HeapTuple  grp_firstTuple; /* copy of first tuple of current group */
  /* these fields are used in AGG_HASHED and AGG_MIXED modes: */
  bool    table_filled;  /* hash table filled yet? */
  int      num_hashes;
  MemoryContext  hash_metacxt;  /* memory for hash table itself */
  struct HashTapeInfo *hash_tapeinfo; /* metadata for spill tapes */
  struct HashAggSpill *hash_spills; /* HashAggSpill for each grouping set,
                     exists only during first pass */
  TupleTableSlot *hash_spill_slot; /* slot for reading from spill files */
  List     *hash_batches;  /* hash batches remaining to be processed */
  bool    hash_ever_spilled;  /* ever spilled during this execution? */
  bool    hash_spill_mode;  /* we hit a limit during the current batch
                     and we must not create new groups */
  Size    hash_mem_limit;  /* limit before spilling hash table */
  uint64    hash_ngroups_limit;  /* limit before spilling hash table */
  int      hash_planned_partitions; /* number of partitions planned
                      for first pass */
  double    hashentrysize;  /* estimate revised during execution */
  Size    hash_mem_peak;  /* peak hash table memory usage */
  uint64    hash_ngroups_current;  /* number of groups currently in
                       memory in all hash tables */
  uint64    hash_disk_used; /* kB of disk space used */
  int      hash_batches_used;  /* batches used during entire execution */

  AggStatePerHash perhash;  /* array of per-hashtable data */
  AggStatePerGroup *hash_pergroup;  /* grouping set indexed array of
                     * per-group pointers */

  /* support for evaluation of agg input expressions: */
#define FIELDNO_AGGSTATE_ALL_PERGROUPS 49
  AggStatePerGroup *all_pergroups;  /* array of first ->pergroups, than
                     * ->hash_pergroup */
  ProjectionInfo *combinedproj;  /* projection machinery */
  int      group_id;    /* GROUP_ID in current projection. This is passed
                 * to GroupingSetId expressions, similar to the
                 * 'grouped_cols' value. */
  int      gset_id;
  /* if input tuple has an AggExprId, save the Attribute Number */
  Index       AggExprId_AttrNum;
} AggState;

typedef enum AggStrategy
{
  AGG_PLAIN,          /* simple agg across all input rows */
  AGG_SORTED,          /* grouped agg, input must be sorted */
  AGG_HASHED,          /* grouped agg, use internal hashtable */
  AGG_MIXED          /* grouped agg, hash and sort both used */
} AggStrategy;