pg_dependencies.c

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/*-------------------------------------------------------------------------
 *
 * pg_dependencies.c
 *      pg_dependencies data type support.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/pg_dependencies.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "common/int.h"
#include "common/jsonapi.h"
#include "lib/stringinfo.h"
#include "mb/pg_wchar.h"
#include "nodes/miscnodes.h"
#include "statistics/extended_stats_internal.h"
#include "statistics/statistics_format.h"
#include "utils/builtins.h"
#include "utils/float.h"
#include "utils/fmgrprotos.h"
 
typedef enum
{
    DEPS_EXPECT_START = 0,
    DEPS_EXPECT_ITEM,
    DEPS_EXPECT_KEY,
    DEPS_EXPECT_ATTNUM_LIST,
    DEPS_EXPECT_ATTNUM,
    DEPS_EXPECT_DEPENDENCY,
    DEPS_EXPECT_DEGREE,
    DEPS_PARSE_COMPLETE,
} DependenciesSemanticState;
 
typedef struct
{
    const char *str;
    DependenciesSemanticState state;
 
    List       *dependency_list;
    Node       *escontext;
 
    bool        found_attributes;   /* Item has an attributes key */
    bool        found_dependency;   /* Item has an dependency key */
    bool        found_degree;   /* Item has degree key */
    List       *attnum_list;    /* Accumulated attribute numbers */
    AttrNumber  dependency;
    double      degree;
} DependenciesParseState;
 
/*
 * Invoked at the start of each MVDependency object.
 *
 * The entire JSON document should be one array of MVDependency objects.
 *
 * If we are anywhere else in the document, it's an error.
 */
static JsonParseErrorType
dependencies_object_start(void *state)
{
    DependenciesParseState *parse = state;
 
    switch (parse->state)
    {
        case DEPS_EXPECT_ITEM:
            /* Now we expect to see attributes/dependency/degree keys */
            parse->state = DEPS_EXPECT_KEY;
            return JSON_SUCCESS;
 
        case DEPS_EXPECT_START:
            /* pg_dependencies must begin with a '[' */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Initial element must be an array."));
            break;
 
        case DEPS_EXPECT_KEY:
            /* In an object, expecting key */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Expected an object key."));
            break;
 
        case DEPS_EXPECT_ATTNUM_LIST:
            /* Just followed an "attributes": key */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Value of \"%s\" must be an array of attribute numbers.",
                              PG_DEPENDENCIES_KEY_ATTRIBUTES));
            break;
 
        case DEPS_EXPECT_ATTNUM:
            /* In an attribute number list, expect only scalar integers */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Attribute lists can only contain attribute numbers."));
            break;
 
        case DEPS_EXPECT_DEPENDENCY:
            /* Just followed a "dependency" key */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Value of \"%s\" must be an integer.",
                              PG_DEPENDENCIES_KEY_DEPENDENCY));
            break;
 
        case DEPS_EXPECT_DEGREE:
            /* Just followed a "degree" key */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Value of \"%s\" must be an integer.",
                              PG_DEPENDENCIES_KEY_DEGREE));
            break;
 
        default:
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Unexpected parse state: %d", (int) parse->state));
            break;
    }
 
    return JSON_SEM_ACTION_FAILED;
}
 
/*
 * Invoked at the end of an object.
 *
 * Handle the end of an MVDependency object's JSON representation.
 */
static JsonParseErrorType
dependencies_object_end(void *state)
{
    DependenciesParseState *parse = state;
 
    MVDependency *dep;
 
    int         natts = 0;
 
    if (parse->state != DEPS_EXPECT_KEY)
    {
        errsave(parse->escontext,
                errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                errdetail("Unexpected parse state: %d", (int) parse->state));
        return JSON_SEM_ACTION_FAILED;
    }
 
    if (!parse->found_attributes)
    {
        errsave(parse->escontext,
                errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                errdetail("Item must contain \"%s\" key",
                          PG_DEPENDENCIES_KEY_ATTRIBUTES));
        return JSON_SEM_ACTION_FAILED;
    }
 
    if (!parse->found_dependency)
    {
        errsave(parse->escontext,
                errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                errdetail("Item must contain \"%s\" key.",
                          PG_DEPENDENCIES_KEY_DEPENDENCY));
        return JSON_SEM_ACTION_FAILED;
    }
 
    if (!parse->found_degree)
    {
        errsave(parse->escontext,
                errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                errdetail("Item must contain \"%s\" key.",
                          PG_DEPENDENCIES_KEY_DEGREE));
        return JSON_SEM_ACTION_FAILED;
    }
 
    /*
     * We need at least one attribute number in a dependencies item, anything
     * less is malformed.
     */
    natts = list_length(parse->attnum_list);
    if ((natts < 1) || (natts > (STATS_MAX_DIMENSIONS - 1)))
    {
        errsave(parse->escontext,
                errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                errdetail("The \"%s\" key must contain an array of at least %d and no more than %d elements.",
                          PG_DEPENDENCIES_KEY_ATTRIBUTES, 1,
                          STATS_MAX_DIMENSIONS - 1));
        return JSON_SEM_ACTION_FAILED;
    }
 
    /*
     * Allocate enough space for the dependency, the attribute numbers in the
     * list and the final attribute number for the dependency.
     */
    dep = palloc0(offsetof(MVDependency, attributes) + ((natts + 1) * sizeof(AttrNumber)));
    dep->nattributes = natts + 1;
 
    dep->attributes[natts] = parse->dependency;
    dep->degree = parse->degree;
 
    /*
     * Assign attribute numbers to the attributes array, comparing each one
     * against the dependency attribute to ensure that there there are no
     * matches.
     */
    for (int i = 0; i < natts; i++)
    {
        dep->attributes[i] = (AttrNumber) list_nth_int(parse->attnum_list, i);
        if (dep->attributes[i] == parse->dependency)
        {
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Item \"%s\" value %d found in the \"%s\" list.",
                              PG_DEPENDENCIES_KEY_DEPENDENCY, parse->dependency,
                              PG_DEPENDENCIES_KEY_ATTRIBUTES));
            return JSON_SEM_ACTION_FAILED;
        }
    }
 
    parse->dependency_list = lappend(parse->dependency_list, (void *) dep);
 
    /*
     * Reset dependency item state variables to look for the next
     * MVDependency.
     */
    list_free(parse->attnum_list);
    parse->attnum_list = NIL;
    parse->dependency = 0;
    parse->degree = 0.0;
    parse->found_attributes = false;
    parse->found_dependency = false;
    parse->found_degree = false;
    parse->state = DEPS_EXPECT_ITEM;
 
    return JSON_SUCCESS;
}
 
/*
 * Invoked at the start of an array.
 *
 * Dependency input format does not have arrays, so any array elements
 * encountered are an error.
 */
static JsonParseErrorType
dependencies_array_start(void *state)
{
    DependenciesParseState *parse = state;
 
    switch (parse->state)
    {
        case DEPS_EXPECT_ATTNUM_LIST:
            parse->state = DEPS_EXPECT_ATTNUM;
            break;
        case DEPS_EXPECT_START:
            parse->state = DEPS_EXPECT_ITEM;
            break;
        default:
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Array found in unexpected place."));
            return JSON_SEM_ACTION_FAILED;
    }
 
    return JSON_SUCCESS;
}
 
/*
 * Invoked at the end of an array.
 *
 * Either the end of an attribute number list or the whole object.
 */
static JsonParseErrorType
dependencies_array_end(void *state)
{
    DependenciesParseState *parse = state;
 
    switch (parse->state)
    {
        case DEPS_EXPECT_ATTNUM:
            if (list_length(parse->attnum_list) > 0)
            {
                parse->state = DEPS_EXPECT_KEY;
                return JSON_SUCCESS;
            }
 
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("The \"%s\" key must be an non-empty array.",
                              PG_DEPENDENCIES_KEY_ATTRIBUTES));
            break;
 
        case DEPS_EXPECT_ITEM:
            if (list_length(parse->dependency_list) > 0)
            {
                parse->state = DEPS_PARSE_COMPLETE;
                return JSON_SUCCESS;
            }
 
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Item array cannot be empty."));
            break;
 
        default:
 
            /*
             * This can only happen if a case was missed in
             * dependencies_array_start().
             */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Array found in unexpected place."));
            break;
    }
    return JSON_SEM_ACTION_FAILED;
}
 
/*
 * Invoked at the start of a key/value field.
 *
 * The valid keys for the MVDependency object are:
 *   - attributes
 *   - dependency
 *   - degree
 */
static JsonParseErrorType
dependencies_object_field_start(void *state, char *fname, bool isnull)
{
    DependenciesParseState *parse = state;
 
    if (strcmp(fname, PG_DEPENDENCIES_KEY_ATTRIBUTES) == 0)
    {
        if (parse->found_attributes)
        {
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Multiple \"%s\" keys are not allowed.",
                              PG_DEPENDENCIES_KEY_ATTRIBUTES));
            return JSON_SEM_ACTION_FAILED;
        }
 
        parse->found_attributes = true;
        parse->state = DEPS_EXPECT_ATTNUM_LIST;
        return JSON_SUCCESS;
    }
 
    if (strcmp(fname, PG_DEPENDENCIES_KEY_DEPENDENCY) == 0)
    {
        if (parse->found_dependency)
        {
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Multiple \"%s\" keys are not allowed.",
                              PG_DEPENDENCIES_KEY_DEPENDENCY));
            return JSON_SEM_ACTION_FAILED;
        }
 
        parse->found_dependency = true;
        parse->state = DEPS_EXPECT_DEPENDENCY;
        return JSON_SUCCESS;
    }
 
    if (strcmp(fname, PG_DEPENDENCIES_KEY_DEGREE) == 0)
    {
        if (parse->found_degree)
        {
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Multiple \"%s\" keys are not allowed.",
                              PG_DEPENDENCIES_KEY_DEGREE));
            return JSON_SEM_ACTION_FAILED;
        }
 
        parse->found_degree = true;
        parse->state = DEPS_EXPECT_DEGREE;
        return JSON_SUCCESS;
    }
 
    errsave(parse->escontext,
            errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
            errmsg("malformed pg_dependencies: \"%s\"", parse->str),
            errdetail("Only allowed keys are \"%s\", \"%s\" and \"%s\".",
                      PG_DEPENDENCIES_KEY_ATTRIBUTES,
                      PG_DEPENDENCIES_KEY_DEPENDENCY,
                      PG_DEPENDENCIES_KEY_DEGREE));
    return JSON_SEM_ACTION_FAILED;
}
 
/*
 * Invoked at the start of an array element.
 *
 * pg_dependencies input format does not have arrays, so any array elements
 * encountered are an error.
 */
static JsonParseErrorType
dependencies_array_element_start(void *state, bool isnull)
{
    DependenciesParseState *parse = state;
 
    switch (parse->state)
    {
        case DEPS_EXPECT_ATTNUM:
            if (!isnull)
                return JSON_SUCCESS;
 
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Attribute number array cannot be null."));
            break;
 
        case DEPS_EXPECT_ITEM:
            if (!isnull)
                return JSON_SUCCESS;
 
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Item list elements cannot be null."));
            break;
 
        default:
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Unexpected array element."));
            break;
    }
 
    return JSON_SEM_ACTION_FAILED;
}
 
/*
 * Test for valid subsequent attribute number.
 *
 * If the previous value is positive, then current value must either be
 * greater than the previous value, or negative.
 *
 * If the previous value is negative, then the value must be less than
 * the previous value.
 *
 * Duplicate values are not allowed; that is already covered by the rules
 * described above.
 */
static bool
valid_subsequent_attnum(const AttrNumber prev, const AttrNumber cur)
{
    Assert(prev != 0);
 
    if (prev > 0)
        return ((cur > prev) || (cur < 0));
 
    return (cur < prev);
}
 
/*
 * Handle scalar events from the dependencies input parser.
 *
 * There is only one case where we will encounter a scalar, and that is the
 * dependency degree for the previous object key.
 */
static JsonParseErrorType
dependencies_scalar(void *state, char *token, JsonTokenType tokentype)
{
    DependenciesParseState *parse = state;
    AttrNumber  attnum;
    ErrorSaveContext escontext = {T_ErrorSaveContext};
 
    switch (parse->state)
    {
        case DEPS_EXPECT_ATTNUM:
            attnum = pg_strtoint16_safe(token, (Node *) &escontext);
 
            if (escontext.error_occurred)
            {
                errsave(parse->escontext,
                        errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                        errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                        errdetail("Invalid \"%s\" value.", PG_DEPENDENCIES_KEY_ATTRIBUTES));
                return JSON_SEM_ACTION_FAILED;
            }
 
            /*
             * An attribute number cannot be zero or a negative number beyond
             * the number of the possible expressions.
             */
            if (attnum == 0 || attnum < (0 - STATS_MAX_DIMENSIONS))
            {
                errsave(parse->escontext,
                        errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                        errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                        errdetail("Invalid \"%s\" element: %d.",
                                  PG_DEPENDENCIES_KEY_ATTRIBUTES, attnum));
                return JSON_SEM_ACTION_FAILED;
            }
 
            if (parse->attnum_list != NIL)
            {
                const AttrNumber prev = llast_int(parse->attnum_list);
 
                if (!valid_subsequent_attnum(prev, attnum))
                {
                    errsave(parse->escontext,
                            errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                            errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                            errdetail("Invalid \"%s\" element: %d cannot follow %d.",
                                      PG_DEPENDENCIES_KEY_ATTRIBUTES, attnum, prev));
                    return JSON_SEM_ACTION_FAILED;
                }
            }
 
            parse->attnum_list = lappend_int(parse->attnum_list, (int) attnum);
            return JSON_SUCCESS;
 
        case DEPS_EXPECT_DEPENDENCY:
            parse->dependency = (AttrNumber)
                pg_strtoint16_safe(token, (Node *) &escontext);
 
            if (escontext.error_occurred)
            {
                errsave(parse->escontext,
                        errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                        errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                        errdetail("Invalid \"%s\" value.", PG_DEPENDENCIES_KEY_DEPENDENCY));
                return JSON_SEM_ACTION_FAILED;
            }
 
            /*
             * The dependency attribute number cannot be zero or a negative
             * number beyond the number of the possible expressions.
             */
            if (parse->dependency == 0 || parse->dependency < (0 - STATS_MAX_DIMENSIONS))
            {
                errsave(parse->escontext,
                        errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                        errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                        errdetail("Invalid \"%s\" value: %d.",
                                  PG_DEPENDENCIES_KEY_DEPENDENCY, parse->dependency));
                return JSON_SEM_ACTION_FAILED;
            }
 
            parse->state = DEPS_EXPECT_KEY;
            return JSON_SUCCESS;
 
        case DEPS_EXPECT_DEGREE:
            parse->degree = float8in_internal(token, NULL, "double",
                                              token, (Node *) &escontext);
 
            if (escontext.error_occurred)
            {
                errsave(parse->escontext,
                        errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                        errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                        errdetail("Invalid \"%s\" value.", PG_DEPENDENCIES_KEY_DEGREE));
                return JSON_SEM_ACTION_FAILED;
            }
 
            parse->state = DEPS_EXPECT_KEY;
            return JSON_SUCCESS;
 
        default:
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", parse->str),
                    errdetail("Unexpected scalar."));
            break;
    }
 
    return JSON_SEM_ACTION_FAILED;
}
 
/*
 * Compare the attribute arrays of two MVDependency values,
 * looking for duplicated sets.
 */
static bool
dep_attributes_eq(const MVDependency *a, const MVDependency *b)
{
    int         i;
 
    if (a->nattributes != b->nattributes)
        return false;
 
    for (i = 0; i < a->nattributes; i++)
    {
        if (a->attributes[i] != b->attributes[i])
            return false;
    }
 
    return true;
}
 
/*
 * Generate a string representing an array of attribute numbers.
 * Internally, the dependency attribute is the last element, so we
 * leave that off.
 *
 * Freeing the allocated string is the responsibility of the caller.
 */
static char *
dep_attnum_list(const MVDependency *item)
{
    StringInfoData str;
 
    initStringInfo(&str);
 
    appendStringInfo(&str, "%d", item->attributes[0]);
 
    for (int i = 1; i < item->nattributes - 1; i++)
        appendStringInfo(&str, ", %d", item->attributes[i]);
 
    return str.data;
}
 
/*
 * Return the dependency, which is the last attribute element.
 */
static AttrNumber
dep_attnum_dependency(const MVDependency *item)
{
    return item->attributes[item->nattributes - 1];
}
 
/*
 * Attempt to build and serialize the MVDependencies object.
 *
 * This can only be executed after the completion of the JSON parsing.
 *
 * In the event of an error, set the error context and return NULL.
 */
static bytea *
build_mvdependencies(DependenciesParseState *parse, char *str)
{
    int         ndeps = list_length(parse->dependency_list);
 
    MVDependencies *mvdeps;
    bytea      *bytes;
 
    switch (parse->state)
    {
        case DEPS_PARSE_COMPLETE:
 
            /*
             * Parse ended in the expected place.  We should have a list of
             * items, but if we do not there is an issue with one of the
             * earlier parse steps.
             */
            if (ndeps == 0)
                elog(ERROR,
                     "pg_dependencies parsing claims success with an empty item list.");
            break;
 
        case DEPS_EXPECT_START:
            /* blank */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", str),
                    errdetail("Value cannot be empty."));
            return NULL;
 
        default:
            /* Unexpected end-state. */
            errsave(parse->escontext,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_dependencies: \"%s\"", str),
                    errdetail("Unexpected end state %d.", parse->state));
            return NULL;
    }
 
    mvdeps = palloc0(offsetof(MVDependencies, deps)
                     + (ndeps * sizeof(MVDependency *)));
    mvdeps->magic = STATS_DEPS_MAGIC;
    mvdeps->type = STATS_DEPS_TYPE_BASIC;
    mvdeps->ndeps = ndeps;
 
    for (int i = 0; i < ndeps; i++)
    {
        /*
         * Use the MVDependency objects in the dependency_list.
         *
         * Because we free the dependency_list after parsing is done, we
         * cannot free it here.
         */
        mvdeps->deps[i] = list_nth(parse->dependency_list, i);
 
        /*
         * Ensure that this item does not duplicate the attributes of any
         * pre-existing item.
         */
        for (int j = 0; j < i; j++)
        {
            if (dep_attributes_eq(mvdeps->deps[i], mvdeps->deps[j]))
            {
                MVDependency *dep = mvdeps->deps[i];
                char       *attnum_list = dep_attnum_list(dep);
                AttrNumber  attnum_dep = dep_attnum_dependency(dep);
 
                errsave(parse->escontext,
                        errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                        errmsg("malformed pg_dependencies: \"%s\"", str),
                        errdetail("Duplicate \"%s\" array: [%s] with \"%s\": %d.",
                                  PG_DEPENDENCIES_KEY_ATTRIBUTES, attnum_list,
                                  PG_DEPENDENCIES_KEY_DEPENDENCY, attnum_dep));
                pfree(mvdeps);
                return NULL;
            }
        }
    }
 
    bytes = statext_dependencies_serialize(mvdeps);
 
    /*
     * No need to free the individual MVDependency objects, because they are
     * still in the dependency_list, and will be freed with that.
     */
    pfree(mvdeps);
 
    return bytes;
}
 
 
/*
 * pg_dependencies_in       - input routine for type pg_dependencies.
 *
 * This format is valid JSON, with the expected format:
 *    [{"attributes": [1,2], "dependency": -1, "degree": 1.0000},
 *     {"attributes": [1,-1], "dependency": 2, "degree": 0.0000},
 *     {"attributes": [2,-1], "dependency": 1, "degree": 1.0000}]
 *
 */
Datum
pg_dependencies_in(PG_FUNCTION_ARGS)
{
    char       *str = PG_GETARG_CSTRING(0);
    bytea      *bytes = NULL;
 
    DependenciesParseState parse_state;
    JsonParseErrorType result;
    JsonLexContext *lex;
    JsonSemAction sem_action;
 
    /* initialize the semantic state */
    parse_state.str = str;
    parse_state.state = DEPS_EXPECT_START;
    parse_state.dependency_list = NIL;
    parse_state.attnum_list = NIL;
    parse_state.dependency = 0;
    parse_state.degree = 0.0;
    parse_state.found_attributes = false;
    parse_state.found_dependency = false;
    parse_state.found_degree = false;
    parse_state.escontext = fcinfo->context;
 
    /* set callbacks */
    sem_action.semstate = (void *) &parse_state;
    sem_action.object_start = dependencies_object_start;
    sem_action.object_end = dependencies_object_end;
    sem_action.array_start = dependencies_array_start;
    sem_action.array_end = dependencies_array_end;
    sem_action.array_element_start = dependencies_array_element_start;
    sem_action.array_element_end = NULL;
    sem_action.object_field_start = dependencies_object_field_start;
    sem_action.object_field_end = NULL;
    sem_action.scalar = dependencies_scalar;
 
    lex = makeJsonLexContextCstringLen(NULL, str, strlen(str), PG_UTF8, true);
 
    result = pg_parse_json(lex, &sem_action);
    freeJsonLexContext(lex);
 
    if (result == JSON_SUCCESS)
        bytes = build_mvdependencies(&parse_state, str);
 
    list_free_deep(parse_state.dependency_list);
    list_free(parse_state.attnum_list);
 
    if (bytes)
        PG_RETURN_BYTEA_P(bytes);
 
    /*
     * If escontext already set, just use that. Anything else is a generic
     * JSON parse error.
     */
    if (!SOFT_ERROR_OCCURRED(parse_state.escontext))
        errsave(parse_state.escontext,
                errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                errmsg("malformed pg_dependencies: \"%s\"", str),
                errdetail("Must be valid JSON."));
 
    PG_RETURN_NULL();
}
 
 
/*
 * pg_dependencies_out      - output routine for type pg_dependencies.
 */
Datum
pg_dependencies_out(PG_FUNCTION_ARGS)
{
    bytea      *data = PG_GETARG_BYTEA_PP(0);
    MVDependencies *dependencies = statext_dependencies_deserialize(data);
    StringInfoData str;
 
    initStringInfo(&str);
    appendStringInfoChar(&str, '[');
 
    for (int i = 0; i < dependencies->ndeps; i++)
    {
        MVDependency *dependency = dependencies->deps[i];
 
        if (i > 0)
            appendStringInfoString(&str, ", ");
 
        if (dependency->nattributes <= 1)
            elog(ERROR, "invalid zero-length nattributes array in MVDependencies");
 
        appendStringInfo(&str, "{\"" PG_DEPENDENCIES_KEY_ATTRIBUTES "\": [%d",
                         dependency->attributes[0]);
 
        for (int j = 1; j < dependency->nattributes - 1; j++)
            appendStringInfo(&str, ", %d", dependency->attributes[j]);
 
        appendStringInfo(&str, "], \"" PG_DEPENDENCIES_KEY_DEPENDENCY "\": %d, "
                         "\"" PG_DEPENDENCIES_KEY_DEGREE "\": %f}",
                         dependency->attributes[dependency->nattributes - 1],
                         dependency->degree);
    }
 
    appendStringInfoChar(&str, ']');
 
    PG_RETURN_CSTRING(str.data);
}
 
/*
 * pg_dependencies_recv     - binary input routine for type pg_dependencies.
 */
Datum
pg_dependencies_recv(PG_FUNCTION_ARGS)
{
    ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("cannot accept a value of type %s", "pg_dependencies")));
 
    PG_RETURN_VOID();           /* keep compiler quiet */
}
 
/*
 * pg_dependencies_send     - binary output routine for type pg_dependencies.
 *
 * Functional dependencies are serialized in a bytea value (although the type
 * is named differently), so let's just send that.
 */
Datum
pg_dependencies_send(PG_FUNCTION_ARGS)
{
    return byteasend(fcinfo);
}