array.h

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/*-------------------------------------------------------------------------
 *
 * array.h
 *    Declarations for Postgres arrays.
 *
 * A standard varlena array has the following internal structure:
 *    <vl_len_>     - standard varlena header word
 *    <ndim>        - number of dimensions of the array
 *    <dataoffset>  - offset to stored data, or 0 if no nulls bitmap
 *    <elemtype>    - element type OID
 *    <dimensions>  - length of each array axis (C array of int)
 *    <lower bnds>  - lower boundary of each dimension (C array of int)
 *    <null bitmap> - bitmap showing locations of nulls (OPTIONAL)
 *    <actual data> - whatever is the stored data
 *
 * The <dimensions> and <lower bnds> arrays each have ndim elements.
 *
 * The <null bitmap> may be omitted if the array contains no NULL elements.
 * If it is absent, the <dataoffset> field is zero and the offset to the
 * stored data must be computed on-the-fly.  If the bitmap is present,
 * <dataoffset> is nonzero and is equal to the offset from the array start
 * to the first data element (including any alignment padding).  The bitmap
 * follows the same conventions as tuple null bitmaps, ie, a 1 indicates
 * a non-null entry and the LSB of each bitmap byte is used first.
 *
 * The actual data starts on a MAXALIGN boundary.  Individual items in the
 * array are aligned as specified by the array element type.  They are
 * stored in row-major order (last subscript varies most rapidly).
 *
 * NOTE: it is important that array elements of toastable datatypes NOT be
 * toasted, since the tupletoaster won't know they are there.  (We could
 * support compressed toasted items; only out-of-line items are dangerous.
 * However, it seems preferable to store such items uncompressed and allow
 * the toaster to compress the whole array as one input.)
 *
 *
 * The OIDVECTOR and INT2VECTOR datatypes are storage-compatible with
 * generic arrays, but they support only one-dimensional arrays with no
 * nulls (and no null bitmap).  They don't support being toasted, either.
 *
 * There are also some "fixed-length array" datatypes, such as NAME and
 * POINT.  These are simply a sequence of a fixed number of items each
 * of a fixed-length datatype, with no overhead; the item size must be
 * a multiple of its alignment requirement, because we do no padding.
 * We support subscripting on these types, but array_in() and array_out()
 * only work with varlena arrays.
 *
 * In addition, arrays are a major user of the "expanded object" TOAST
 * infrastructure.  This allows a varlena array to be converted to a
 * separate representation that may include "deconstructed" Datum/isnull
 * arrays holding the elements.
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/array.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef ARRAY_H
#define ARRAY_H

#include "fmgr.h"
#include "utils/expandeddatum.h"

/* avoid including execnodes.h here */
struct ExprState;
struct ExprContext;


/*
 * Maximum number of array subscripts (arbitrary limit)
 */
#define MAXDIM 6

/*
 * Arrays are varlena objects, so must meet the varlena convention that
 * the first int32 of the object contains the total object size in bytes.
 * Be sure to use VARSIZE() and SET_VARSIZE() to access it, though!
 *
 * CAUTION: if you change the header for ordinary arrays you will also
 * need to change the headers for oidvector and int2vector!
 */
typedef struct ArrayType
{
    int32       vl_len_;        /* varlena header (do not touch directly!) */
    int         ndim;           /* # of dimensions */
    int32       dataoffset;     /* offset to data, or 0 if no bitmap */
    Oid         elemtype;       /* element type OID */
} ArrayType;

/*
 * An expanded array is contained within a private memory context (as
 * all expanded objects must be) and has a control structure as below.
 *
 * The expanded array might contain a regular "flat" array if that was the
 * original input and we've not modified it significantly.  Otherwise, the
 * contents are represented by Datum/isnull arrays plus dimensionality and
 * type information.  We could also have both forms, if we've deconstructed
 * the original array for access purposes but not yet changed it.  For pass-
 * by-reference element types, the Datums would point into the flat array in
 * this situation.  Once we start modifying array elements, new pass-by-ref
 * elements are separately palloc'd within the memory context.
 */
#define EA_MAGIC 689375833      /* ID for debugging crosschecks */

typedef struct ExpandedArrayHeader
{
    /* Standard header for expanded objects */
    ExpandedObjectHeader hdr;

    /* Magic value identifying an expanded array (for debugging only) */
    int         ea_magic;

    /* Dimensionality info (always valid) */
    int         ndims;          /* # of dimensions */
    int        *dims;           /* array dimensions */
    int        *lbound;         /* index lower bounds for each dimension */

    /* Element type info (always valid) */
    Oid         element_type;   /* element type OID */
    int16       typlen;         /* needed info about element datatype */
    bool        typbyval;
    char        typalign;

    /*
     * If we have a Datum-array representation of the array, it's kept here;
     * else dvalues/dnulls are NULL.  The dvalues and dnulls arrays are always
     * palloc'd within the object private context, but may change size from
     * time to time.  For pass-by-ref element types, dvalues entries might
     * point either into the fstartptr..fendptr area, or to separately
     * palloc'd chunks.  Elements should always be fully detoasted, as they
     * are in the standard flat representation.
     *
     * Even when dvalues is valid, dnulls can be NULL if there are no null
     * elements.
     */
    Datum      *dvalues;        /* array of Datums */
    bool       *dnulls;         /* array of is-null flags for Datums */
    int         dvalueslen;     /* allocated length of above arrays */
    int         nelems;         /* number of valid entries in above arrays */

    /*
     * flat_size is the current space requirement for the flat equivalent of
     * the expanded array, if known; otherwise it's 0.  We store this to make
     * consecutive calls of get_flat_size cheap.
     */
    Size        flat_size;

    /*
     * fvalue points to the flat representation if it is valid, else it is
     * NULL.  If we have or ever had a flat representation then
     * fstartptr/fendptr point to the start and end+1 of its data area; this
     * is so that we can tell which Datum pointers point into the flat
     * representation rather than being pointers to separately palloc'd data.
     */
    ArrayType  *fvalue;         /* must be a fully detoasted array */
    char       *fstartptr;      /* start of its data area */
    char       *fendptr;        /* end+1 of its data area */
} ExpandedArrayHeader;

/*
 * Functions that can handle either a "flat" varlena array or an expanded
 * array use this union to work with their input.  Don't refer to "flt";
 * instead, cast to ArrayType.  This struct nominally requires 8-byte
 * alignment on 64-bit, but it's often used for an ArrayType having 4-byte
 * alignment.  UBSan complains about referencing "flt" in such cases.
 */
typedef union AnyArrayType
{
    ArrayType   flt;
    ExpandedArrayHeader xpn;
} AnyArrayType;

/*
 * working state for accumArrayResult() and friends
 * note that the input must be scalars (legal array elements)
 */
typedef struct ArrayBuildState
{
    MemoryContext mcontext;     /* where all the temp stuff is kept */
    Datum      *dvalues;        /* array of accumulated Datums */
    bool       *dnulls;         /* array of is-null flags for Datums */
    int         alen;           /* allocated length of above arrays */
    int         nelems;         /* number of valid entries in above arrays */
    Oid         element_type;   /* data type of the Datums */
    int16       typlen;         /* needed info about datatype */
    bool        typbyval;
    char        typalign;
    bool        private_cxt;    /* use private memory context */
} ArrayBuildState;

/*
 * working state for accumArrayResultArr() and friends
 * note that the input must be arrays, and the same array type is returned
 */
typedef struct ArrayBuildStateArr
{
    MemoryContext mcontext;     /* where all the temp stuff is kept */
    char       *data;           /* accumulated data */
    bits8      *nullbitmap;     /* bitmap of is-null flags, or NULL if none */
    int         abytes;         /* allocated length of "data" */
    int         nbytes;         /* number of bytes used so far */
    int         aitems;         /* allocated length of bitmap (in elements) */
    int         nitems;         /* total number of elements in result */
    int         ndims;          /* current dimensions of result */
    int         dims[MAXDIM];
    int         lbs[MAXDIM];
    Oid         array_type;     /* data type of the arrays */
    Oid         element_type;   /* data type of the array elements */
    bool        private_cxt;    /* use private memory context */
} ArrayBuildStateArr;

/*
 * working state for accumArrayResultAny() and friends
 * these functions handle both cases
 */
typedef struct ArrayBuildStateAny
{
    /* Exactly one of these is not NULL: */
    ArrayBuildState *scalarstate;
    ArrayBuildStateArr *arraystate;
} ArrayBuildStateAny;

/*
 * structure to cache type metadata needed for array manipulation
 */
typedef struct ArrayMetaState
{
    Oid         element_type;
    int16       typlen;
    bool        typbyval;
    char        typalign;
    char        typdelim;
    Oid         typioparam;
    Oid         typiofunc;
    FmgrInfo    proc;
} ArrayMetaState;

/*
 * private state needed by array_map (here because caller must provide it)
 */
typedef struct ArrayMapState
{
    ArrayMetaState inp_extra;
    ArrayMetaState ret_extra;
} ArrayMapState;

/* ArrayIteratorData is private in arrayfuncs.c */
typedef struct ArrayIteratorData *ArrayIterator;

/* fmgr macros for regular varlena array objects */
#define DatumGetArrayTypeP(X)         ((ArrayType *) PG_DETOAST_DATUM(X))
#define DatumGetArrayTypePCopy(X)     ((ArrayType *) PG_DETOAST_DATUM_COPY(X))
#define PG_GETARG_ARRAYTYPE_P(n)      DatumGetArrayTypeP(PG_GETARG_DATUM(n))
#define PG_GETARG_ARRAYTYPE_P_COPY(n) DatumGetArrayTypePCopy(PG_GETARG_DATUM(n))
#define PG_RETURN_ARRAYTYPE_P(x)      PG_RETURN_POINTER(x)

/* fmgr macros for expanded array objects */
#define PG_GETARG_EXPANDED_ARRAY(n)  DatumGetExpandedArray(PG_GETARG_DATUM(n))
#define PG_GETARG_EXPANDED_ARRAYX(n, metacache) \
    DatumGetExpandedArrayX(PG_GETARG_DATUM(n), metacache)
#define PG_RETURN_EXPANDED_ARRAY(x)  PG_RETURN_DATUM(EOHPGetRWDatum(&(x)->hdr))

/* fmgr macros for AnyArrayType (ie, get either varlena or expanded form) */
#define PG_GETARG_ANY_ARRAY_P(n)    DatumGetAnyArrayP(PG_GETARG_DATUM(n))

/*
 * Access macros for varlena array header fields.
 *
 * ARR_DIMS returns a pointer to an array of array dimensions (number of
 * elements along the various array axes).
 *
 * ARR_LBOUND returns a pointer to an array of array lower bounds.
 *
 * That is: if the third axis of an array has elements 5 through 8, then
 * ARR_DIMS(a)[2] == 4 and ARR_LBOUND(a)[2] == 5.
 *
 * Unlike C, the default lower bound is 1.
 */
#define ARR_SIZE(a)             VARSIZE(a)
#define ARR_NDIM(a)             ((a)->ndim)
#define ARR_HASNULL(a)          ((a)->dataoffset != 0)
#define ARR_ELEMTYPE(a)         ((a)->elemtype)

#define ARR_DIMS(a) \
        ((int *) (((char *) (a)) + sizeof(ArrayType)))
#define ARR_LBOUND(a) \
        ((int *) (((char *) (a)) + sizeof(ArrayType) + \
                  sizeof(int) * ARR_NDIM(a)))

#define ARR_NULLBITMAP(a) \
        (ARR_HASNULL(a) ? \
         (bits8 *) (((char *) (a)) + sizeof(ArrayType) + \
                    2 * sizeof(int) * ARR_NDIM(a)) \
         : (bits8 *) NULL)

/*
 * The total array header size (in bytes) for an array with the specified
 * number of dimensions and total number of items.
 */
#define ARR_OVERHEAD_NONULLS(ndims) \
        MAXALIGN(sizeof(ArrayType) + 2 * sizeof(int) * (ndims))
#define ARR_OVERHEAD_WITHNULLS(ndims, nitems) \
        MAXALIGN(sizeof(ArrayType) + 2 * sizeof(int) * (ndims) + \
                 ((nitems) + 7) / 8)

#define ARR_DATA_OFFSET(a) \
        (ARR_HASNULL(a) ? (a)->dataoffset : ARR_OVERHEAD_NONULLS(ARR_NDIM(a)))

/*
 * Returns a pointer to the actual array data.
 */
#define ARR_DATA_PTR(a) \
        (((char *) (a)) + ARR_DATA_OFFSET(a))

/*
 * Macros for working with AnyArrayType inputs.  Beware multiple references!
 */
#define AARR_NDIM(a) \
    (VARATT_IS_EXPANDED_HEADER(a) ? \
     (a)->xpn.ndims : ARR_NDIM((ArrayType *) (a)))
#define AARR_HASNULL(a) \
    (VARATT_IS_EXPANDED_HEADER(a) ? \
     ((a)->xpn.dvalues != NULL ? (a)->xpn.dnulls != NULL : ARR_HASNULL((a)->xpn.fvalue)) : \
     ARR_HASNULL((ArrayType *) (a)))
#define AARR_ELEMTYPE(a) \
    (VARATT_IS_EXPANDED_HEADER(a) ? \
     (a)->xpn.element_type : ARR_ELEMTYPE((ArrayType *) (a)))
#define AARR_DIMS(a) \
    (VARATT_IS_EXPANDED_HEADER(a) ? \
     (a)->xpn.dims : ARR_DIMS((ArrayType *) (a)))
#define AARR_LBOUND(a) \
    (VARATT_IS_EXPANDED_HEADER(a) ? \
     (a)->xpn.lbound : ARR_LBOUND((ArrayType *) (a)))


/*
 * GUC parameter
 */
extern bool Array_nulls;

/*
 * prototypes for functions defined in arrayfuncs.c
 */
extern void CopyArrayEls(ArrayType *array,
                         Datum *values,
                         bool *nulls,
                         int nitems,
                         int typlen,
                         bool typbyval,
                         char typalign,
                         bool freedata);

extern Datum array_get_element(Datum arraydatum, int nSubscripts, int *indx,
                               int arraytyplen, int elmlen, bool elmbyval, char elmalign,
                               bool *isNull);
extern Datum array_set_element(Datum arraydatum, int nSubscripts, int *indx,
                               Datum dataValue, bool isNull,
                               int arraytyplen, int elmlen, bool elmbyval, char elmalign);
extern Datum array_get_slice(Datum arraydatum, int nSubscripts,
                             int *upperIndx, int *lowerIndx,
                             bool *upperProvided, bool *lowerProvided,
                             int arraytyplen, int elmlen, bool elmbyval, char elmalign);
extern Datum array_set_slice(Datum arraydatum, int nSubscripts,
                             int *upperIndx, int *lowerIndx,
                             bool *upperProvided, bool *lowerProvided,
                             Datum srcArrayDatum, bool isNull,
                             int arraytyplen, int elmlen, bool elmbyval, char elmalign);

extern Datum array_ref(ArrayType *array, int nSubscripts, int *indx,
                       int arraytyplen, int elmlen, bool elmbyval, char elmalign,
                       bool *isNull);
extern ArrayType *array_set(ArrayType *array, int nSubscripts, int *indx,
                            Datum dataValue, bool isNull,
                            int arraytyplen, int elmlen, bool elmbyval, char elmalign);

extern Datum array_map(Datum arrayd,
                       struct ExprState *exprstate, struct ExprContext *econtext,
                       Oid retType, ArrayMapState *amstate);

extern void array_bitmap_copy(bits8 *destbitmap, int destoffset,
                              const bits8 *srcbitmap, int srcoffset,
                              int nitems);

extern ArrayType *construct_array(Datum *elems, int nelems,
                                  Oid elmtype,
                                  int elmlen, bool elmbyval, char elmalign);
extern ArrayType *construct_md_array(Datum *elems,
                                     bool *nulls,
                                     int ndims,
                                     int *dims,
                                     int *lbs,
                                     Oid elmtype, int elmlen, bool elmbyval, char elmalign);
extern ArrayType *construct_empty_array(Oid elmtype);
extern ExpandedArrayHeader *construct_empty_expanded_array(Oid element_type,
                                                           MemoryContext parentcontext,
                                                           ArrayMetaState *metacache);
extern void deconstruct_array(ArrayType *array,
                              Oid elmtype,
                              int elmlen, bool elmbyval, char elmalign,
                              Datum **elemsp, bool **nullsp, int *nelemsp);
extern bool array_contains_nulls(ArrayType *array);

extern ArrayBuildState *initArrayResult(Oid element_type,
                                        MemoryContext rcontext, bool subcontext);
extern ArrayBuildState *accumArrayResult(ArrayBuildState *astate,
                                         Datum dvalue, bool disnull,
                                         Oid element_type,
                                         MemoryContext rcontext);
extern Datum makeArrayResult(ArrayBuildState *astate,
                             MemoryContext rcontext);
extern Datum makeMdArrayResult(ArrayBuildState *astate, int ndims,
                               int *dims, int *lbs, MemoryContext rcontext, bool release);

extern ArrayBuildStateArr *initArrayResultArr(Oid array_type, Oid element_type,
                                              MemoryContext rcontext, bool subcontext);
extern ArrayBuildStateArr *accumArrayResultArr(ArrayBuildStateArr *astate,
                                               Datum dvalue, bool disnull,
                                               Oid array_type,
                                               MemoryContext rcontext);
extern Datum makeArrayResultArr(ArrayBuildStateArr *astate,
                                MemoryContext rcontext, bool release);

extern ArrayBuildStateAny *initArrayResultAny(Oid input_type,
                                              MemoryContext rcontext, bool subcontext);
extern ArrayBuildStateAny *accumArrayResultAny(ArrayBuildStateAny *astate,
                                               Datum dvalue, bool disnull,
                                               Oid input_type,
                                               MemoryContext rcontext);
extern Datum makeArrayResultAny(ArrayBuildStateAny *astate,
                                MemoryContext rcontext, bool release);

extern ArrayIterator array_create_iterator(ArrayType *arr, int slice_ndim, ArrayMetaState *mstate);
extern bool array_iterate(ArrayIterator iterator, Datum *value, bool *isnull);
extern void array_free_iterator(ArrayIterator iterator);

/*
 * prototypes for functions defined in arrayutils.c
 */

extern int  ArrayGetOffset(int n, const int *dim, const int *lb, const int *indx);
extern int  ArrayGetOffset0(int n, const int *tup, const int *scale);
extern int  ArrayGetNItems(int ndim, const int *dims);
extern void mda_get_range(int n, int *span, const int *st, const int *endp);
extern void mda_get_prod(int n, const int *range, int *prod);
extern void mda_get_offset_values(int n, int *dist, const int *prod, const int *span);
extern int  mda_next_tuple(int n, int *curr, const int *span);
extern int32 *ArrayGetIntegerTypmods(ArrayType *arr, int *n);

/*
 * prototypes for functions defined in array_expanded.c
 */
extern Datum expand_array(Datum arraydatum, MemoryContext parentcontext,
                          ArrayMetaState *metacache);
extern ExpandedArrayHeader *DatumGetExpandedArray(Datum d);
extern ExpandedArrayHeader *DatumGetExpandedArrayX(Datum d,
                                                   ArrayMetaState *metacache);
extern AnyArrayType *DatumGetAnyArrayP(Datum d);
extern void deconstruct_expanded_array(ExpandedArrayHeader *eah);

#endif                          /* ARRAY_H */