reloptions.c

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/*-------------------------------------------------------------------------
 *
 * reloptions.c
 *    Core support for relation options (pg_class.reloptions)
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/access/common/reloptions.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <float.h>

#include "access/gist_private.h"
#include "access/hash.h"
#include "access/htup_details.h"
#include "access/nbtree.h"
#include "access/reloptions.h"
#include "access/spgist.h"
#include "access/tuptoaster.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "commands/tablespace.h"
#include "commands/view.h"
#include "nodes/makefuncs.h"
#include "postmaster/postmaster.h"
#include "utils/array.h"
#include "utils/attoptcache.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/rel.h"

/*
 * Contents of pg_class.reloptions
 *
 * To add an option:
 *
 * (i) decide on a type (integer, real, bool, string), name, default value,
 * upper and lower bounds (if applicable); for strings, consider a validation
 * routine.
 * (ii) add a record below (or use add_<type>_reloption).
 * (iii) add it to the appropriate options struct (perhaps StdRdOptions)
 * (iv) add it to the appropriate handling routine (perhaps
 * default_reloptions)
 * (v) make sure the lock level is set correctly for that operation
 * (vi) don't forget to document the option
 *
 * The default choice for any new option should be AccessExclusiveLock.
 * In some cases the lock level can be reduced from there, but the lock
 * level chosen should always conflict with itself to ensure that multiple
 * changes aren't lost when we attempt concurrent changes.
 * The choice of lock level depends completely upon how that parameter
 * is used within the server, not upon how and when you'd like to change it.
 * Safety first. Existing choices are documented here, and elsewhere in
 * backend code where the parameters are used.
 *
 * In general, anything that affects the results obtained from a SELECT must be
 * protected by AccessExclusiveLock.
 *
 * Autovacuum related parameters can be set at ShareUpdateExclusiveLock
 * since they are only used by the AV procs and don't change anything
 * currently executing.
 *
 * Fillfactor can be set because it applies only to subsequent changes made to
 * data blocks, as documented in hio.c
 *
 * n_distinct options can be set at ShareUpdateExclusiveLock because they
 * are only used during ANALYZE, which uses a ShareUpdateExclusiveLock,
 * so the ANALYZE will not be affected by in-flight changes. Changing those
 * values has no effect until the next ANALYZE, so no need for stronger lock.
 *
 * Planner-related parameters can be set with ShareUpdateExclusiveLock because
 * they only affect planning and not the correctness of the execution. Plans
 * cannot be changed in mid-flight, so changes here could not easily result in
 * new improved plans in any case. So we allow existing queries to continue
 * and existing plans to survive, a small price to pay for allowing better
 * plans to be introduced concurrently without interfering with users.
 *
 * Setting parallel_workers is safe, since it acts the same as
 * max_parallel_workers_per_gather which is a USERSET parameter that doesn't
 * affect existing plans or queries.
 *
 * vacuum_truncate can be set at ShareUpdateExclusiveLock because it
 * is only used during VACUUM, which uses a ShareUpdateExclusiveLock,
 * so the VACUUM will not be affected by in-flight changes. Changing its
 * value has no effect until the next VACUUM, so no need for stronger lock.
 */

static relopt_bool boolRelOpts[] =
{
    {
        {
            "autosummarize",
            "Enables automatic summarization on this BRIN index",
            RELOPT_KIND_BRIN,
            AccessExclusiveLock
        },
        false
    },
    {
        {
            "autovacuum_enabled",
            "Enables autovacuum in this relation",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        true
    },
    {
        {
            "user_catalog_table",
            "Declare a table as an additional catalog table, e.g. for the purpose of logical replication",
            RELOPT_KIND_HEAP,
            AccessExclusiveLock
        },
        false
    },
    {
        {
            "fastupdate",
            "Enables \"fast update\" feature for this GIN index",
            RELOPT_KIND_GIN,
            AccessExclusiveLock
        },
        true
    },
    {
        {
            "security_barrier",
            "View acts as a row security barrier",
            RELOPT_KIND_VIEW,
            AccessExclusiveLock
        },
        false
    },
    {
        {
            "vacuum_index_cleanup",
            "Enables index vacuuming and index cleanup",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        true
    },
    {
        {
            "vacuum_truncate",
            "Enables vacuum to truncate empty pages at the end of this table",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        true
    },
    /* list terminator */
    {{NULL}}
};

static relopt_int intRelOpts[] =
{
    {
        {
            "fillfactor",
            "Packs table pages only to this percentage",
            RELOPT_KIND_HEAP,
            ShareUpdateExclusiveLock    /* since it applies only to later
                                         * inserts */
        },
        HEAP_DEFAULT_FILLFACTOR, HEAP_MIN_FILLFACTOR, 100
    },
    {
        {
            "fillfactor",
            "Packs btree index pages only to this percentage",
            RELOPT_KIND_BTREE,
            ShareUpdateExclusiveLock    /* since it applies only to later
                                         * inserts */
        },
        BTREE_DEFAULT_FILLFACTOR, BTREE_MIN_FILLFACTOR, 100
    },
    {
        {
            "fillfactor",
            "Packs hash index pages only to this percentage",
            RELOPT_KIND_HASH,
            ShareUpdateExclusiveLock    /* since it applies only to later
                                         * inserts */
        },
        HASH_DEFAULT_FILLFACTOR, HASH_MIN_FILLFACTOR, 100
    },
    {
        {
            "fillfactor",
            "Packs gist index pages only to this percentage",
            RELOPT_KIND_GIST,
            ShareUpdateExclusiveLock    /* since it applies only to later
                                         * inserts */
        },
        GIST_DEFAULT_FILLFACTOR, GIST_MIN_FILLFACTOR, 100
    },
    {
        {
            "fillfactor",
            "Packs spgist index pages only to this percentage",
            RELOPT_KIND_SPGIST,
            ShareUpdateExclusiveLock    /* since it applies only to later
                                         * inserts */
        },
        SPGIST_DEFAULT_FILLFACTOR, SPGIST_MIN_FILLFACTOR, 100
    },
    {
        {
            "autovacuum_vacuum_threshold",
            "Minimum number of tuple updates or deletes prior to vacuum",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 0, INT_MAX
    },
    {
        {
            "autovacuum_analyze_threshold",
            "Minimum number of tuple inserts, updates or deletes prior to analyze",
            RELOPT_KIND_HEAP,
            ShareUpdateExclusiveLock
        },
        -1, 0, INT_MAX
    },
    {
        {
            "autovacuum_vacuum_cost_limit",
            "Vacuum cost amount available before napping, for autovacuum",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 1, 10000
    },
    {
        {
            "autovacuum_freeze_min_age",
            "Minimum age at which VACUUM should freeze a table row, for autovacuum",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 0, 1000000000
    },
    {
        {
            "autovacuum_multixact_freeze_min_age",
            "Minimum multixact age at which VACUUM should freeze a row multixact's, for autovacuum",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 0, 1000000000
    },
    {
        {
            "autovacuum_freeze_max_age",
            "Age at which to autovacuum a table to prevent transaction ID wraparound",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 100000, 2000000000
    },
    {
        {
            "autovacuum_multixact_freeze_max_age",
            "Multixact age at which to autovacuum a table to prevent multixact wraparound",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 10000, 2000000000
    },
    {
        {
            "autovacuum_freeze_table_age",
            "Age at which VACUUM should perform a full table sweep to freeze row versions",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        }, -1, 0, 2000000000
    },
    {
        {
            "autovacuum_multixact_freeze_table_age",
            "Age of multixact at which VACUUM should perform a full table sweep to freeze row versions",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        }, -1, 0, 2000000000
    },
    {
        {
            "log_autovacuum_min_duration",
            "Sets the minimum execution time above which autovacuum actions will be logged",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, -1, INT_MAX
    },
    {
        {
            "toast_tuple_target",
            "Sets the target tuple length at which external columns will be toasted",
            RELOPT_KIND_HEAP,
            ShareUpdateExclusiveLock
        },
        TOAST_TUPLE_TARGET, 128, TOAST_TUPLE_TARGET_MAIN
    },
    {
        {
            "pages_per_range",
            "Number of pages that each page range covers in a BRIN index",
            RELOPT_KIND_BRIN,
            AccessExclusiveLock
        }, 128, 1, 131072
    },
    {
        {
            "gin_pending_list_limit",
            "Maximum size of the pending list for this GIN index, in kilobytes.",
            RELOPT_KIND_GIN,
            AccessExclusiveLock
        },
        -1, 64, MAX_KILOBYTES
    },
    {
        {
            "effective_io_concurrency",
            "Number of simultaneous requests that can be handled efficiently by the disk subsystem.",
            RELOPT_KIND_TABLESPACE,
            ShareUpdateExclusiveLock
        },
#ifdef USE_PREFETCH
        -1, 0, MAX_IO_CONCURRENCY
#else
        0, 0, 0
#endif
    },
    {
        {
            "parallel_workers",
            "Number of parallel processes that can be used per executor node for this relation.",
            RELOPT_KIND_HEAP,
            ShareUpdateExclusiveLock
        },
        -1, 0, 1024
    },

    /* list terminator */
    {{NULL}}
};

static relopt_real realRelOpts[] =
{
    {
        {
            "autovacuum_vacuum_cost_delay",
            "Vacuum cost delay in milliseconds, for autovacuum",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 0.0, 100.0
    },
    {
        {
            "autovacuum_vacuum_scale_factor",
            "Number of tuple updates or deletes prior to vacuum as a fraction of reltuples",
            RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
            ShareUpdateExclusiveLock
        },
        -1, 0.0, 100.0
    },
    {
        {
            "autovacuum_analyze_scale_factor",
            "Number of tuple inserts, updates or deletes prior to analyze as a fraction of reltuples",
            RELOPT_KIND_HEAP,
            ShareUpdateExclusiveLock
        },
        -1, 0.0, 100.0
    },
    {
        {
            "seq_page_cost",
            "Sets the planner's estimate of the cost of a sequentially fetched disk page.",
            RELOPT_KIND_TABLESPACE,
            ShareUpdateExclusiveLock
        },
        -1, 0.0, DBL_MAX
    },
    {
        {
            "random_page_cost",
            "Sets the planner's estimate of the cost of a nonsequentially fetched disk page.",
            RELOPT_KIND_TABLESPACE,
            ShareUpdateExclusiveLock
        },
        -1, 0.0, DBL_MAX
    },
    {
        {
            "n_distinct",
            "Sets the planner's estimate of the number of distinct values appearing in a column (excluding child relations).",
            RELOPT_KIND_ATTRIBUTE,
            ShareUpdateExclusiveLock
        },
        0, -1.0, DBL_MAX
    },
    {
        {
            "n_distinct_inherited",
            "Sets the planner's estimate of the number of distinct values appearing in a column (including child relations).",
            RELOPT_KIND_ATTRIBUTE,
            ShareUpdateExclusiveLock
        },
        0, -1.0, DBL_MAX
    },
    {
        {
            "vacuum_cleanup_index_scale_factor",
            "Number of tuple inserts prior to index cleanup as a fraction of reltuples.",
            RELOPT_KIND_BTREE,
            ShareUpdateExclusiveLock
        },
        -1, 0.0, 1e10
    },
    /* list terminator */
    {{NULL}}
};

static relopt_string stringRelOpts[] =
{
    {
        {
            "buffering",
            "Enables buffering build for this GiST index",
            RELOPT_KIND_GIST,
            AccessExclusiveLock
        },
        4,
        false,
        gistValidateBufferingOption,
        "auto"
    },
    {
        {
            "check_option",
            "View has WITH CHECK OPTION defined (local or cascaded).",
            RELOPT_KIND_VIEW,
            AccessExclusiveLock
        },
        0,
        true,
        validateWithCheckOption,
        NULL
    },
    /* list terminator */
    {{NULL}}
};

static relopt_gen **relOpts = NULL;
static bits32 last_assigned_kind = RELOPT_KIND_LAST_DEFAULT;

static int  num_custom_options = 0;
static relopt_gen **custom_options = NULL;
static bool need_initialization = true;

static void initialize_reloptions(void);
static void parse_one_reloption(relopt_value *option, char *text_str,
                                int text_len, bool validate);

/*
 * initialize_reloptions
 *      initialization routine, must be called before parsing
 *
 * Initialize the relOpts array and fill each variable's type and name length.
 */
static void
initialize_reloptions(void)
{
    int         i;
    int         j;

    j = 0;
    for (i = 0; boolRelOpts[i].gen.name; i++)
    {
        Assert(DoLockModesConflict(boolRelOpts[i].gen.lockmode,
                                   boolRelOpts[i].gen.lockmode));
        j++;
    }
    for (i = 0; intRelOpts[i].gen.name; i++)
    {
        Assert(DoLockModesConflict(intRelOpts[i].gen.lockmode,
                                   intRelOpts[i].gen.lockmode));
        j++;
    }
    for (i = 0; realRelOpts[i].gen.name; i++)
    {
        Assert(DoLockModesConflict(realRelOpts[i].gen.lockmode,
                                   realRelOpts[i].gen.lockmode));
        j++;
    }
    for (i = 0; stringRelOpts[i].gen.name; i++)
    {
        Assert(DoLockModesConflict(stringRelOpts[i].gen.lockmode,
                                   stringRelOpts[i].gen.lockmode));
        j++;
    }
    j += num_custom_options;

    if (relOpts)
        pfree(relOpts);
    relOpts = MemoryContextAlloc(TopMemoryContext,
                                 (j + 1) * sizeof(relopt_gen *));

    j = 0;
    for (i = 0; boolRelOpts[i].gen.name; i++)
    {
        relOpts[j] = &boolRelOpts[i].gen;
        relOpts[j]->type = RELOPT_TYPE_BOOL;
        relOpts[j]->namelen = strlen(relOpts[j]->name);
        j++;
    }

    for (i = 0; intRelOpts[i].gen.name; i++)
    {
        relOpts[j] = &intRelOpts[i].gen;
        relOpts[j]->type = RELOPT_TYPE_INT;
        relOpts[j]->namelen = strlen(relOpts[j]->name);
        j++;
    }

    for (i = 0; realRelOpts[i].gen.name; i++)
    {
        relOpts[j] = &realRelOpts[i].gen;
        relOpts[j]->type = RELOPT_TYPE_REAL;
        relOpts[j]->namelen = strlen(relOpts[j]->name);
        j++;
    }

    for (i = 0; stringRelOpts[i].gen.name; i++)
    {
        relOpts[j] = &stringRelOpts[i].gen;
        relOpts[j]->type = RELOPT_TYPE_STRING;
        relOpts[j]->namelen = strlen(relOpts[j]->name);
        j++;
    }

    for (i = 0; i < num_custom_options; i++)
    {
        relOpts[j] = custom_options[i];
        j++;
    }

    /* add a list terminator */
    relOpts[j] = NULL;

    /* flag the work is complete */
    need_initialization = false;
}

/*
 * add_reloption_kind
 *      Create a new relopt_kind value, to be used in custom reloptions by
 *      user-defined AMs.
 */
relopt_kind
add_reloption_kind(void)
{
    /* don't hand out the last bit so that the enum's behavior is portable */
    if (last_assigned_kind >= RELOPT_KIND_MAX)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("user-defined relation parameter types limit exceeded")));
    last_assigned_kind <<= 1;
    return (relopt_kind) last_assigned_kind;
}

/*
 * add_reloption
 *      Add an already-created custom reloption to the list, and recompute the
 *      main parser table.
 */
static void
add_reloption(relopt_gen *newoption)
{
    static int  max_custom_options = 0;

    if (num_custom_options >= max_custom_options)
    {
        MemoryContext oldcxt;

        oldcxt = MemoryContextSwitchTo(TopMemoryContext);

        if (max_custom_options == 0)
        {
            max_custom_options = 8;
            custom_options = palloc(max_custom_options * sizeof(relopt_gen *));
        }
        else
        {
            max_custom_options *= 2;
            custom_options = repalloc(custom_options,
                                      max_custom_options * sizeof(relopt_gen *));
        }
        MemoryContextSwitchTo(oldcxt);
    }
    custom_options[num_custom_options++] = newoption;

    need_initialization = true;
}

/*
 * allocate_reloption
 *      Allocate a new reloption and initialize the type-agnostic fields
 *      (for types other than string)
 */
static relopt_gen *
allocate_reloption(bits32 kinds, int type, const char *name, const char *desc)
{
    MemoryContext oldcxt;
    size_t      size;
    relopt_gen *newoption;

    oldcxt = MemoryContextSwitchTo(TopMemoryContext);

    switch (type)
    {
        case RELOPT_TYPE_BOOL:
            size = sizeof(relopt_bool);
            break;
        case RELOPT_TYPE_INT:
            size = sizeof(relopt_int);
            break;
        case RELOPT_TYPE_REAL:
            size = sizeof(relopt_real);
            break;
        case RELOPT_TYPE_STRING:
            size = sizeof(relopt_string);
            break;
        default:
            elog(ERROR, "unsupported reloption type %d", type);
            return NULL;        /* keep compiler quiet */
    }

    newoption = palloc(size);

    newoption->name = pstrdup(name);
    if (desc)
        newoption->desc = pstrdup(desc);
    else
        newoption->desc = NULL;
    newoption->kinds = kinds;
    newoption->namelen = strlen(name);
    newoption->type = type;

    MemoryContextSwitchTo(oldcxt);

    return newoption;
}

/*
 * add_bool_reloption
 *      Add a new boolean reloption
 */
void
add_bool_reloption(bits32 kinds, const char *name, const char *desc, bool default_val)
{
    relopt_bool *newoption;

    newoption = (relopt_bool *) allocate_reloption(kinds, RELOPT_TYPE_BOOL,
                                                   name, desc);
    newoption->default_val = default_val;

    add_reloption((relopt_gen *) newoption);
}

/*
 * add_int_reloption
 *      Add a new integer reloption
 */
void
add_int_reloption(bits32 kinds, const char *name, const char *desc, int default_val,
                  int min_val, int max_val)
{
    relopt_int *newoption;

    newoption = (relopt_int *) allocate_reloption(kinds, RELOPT_TYPE_INT,
                                                  name, desc);
    newoption->default_val = default_val;
    newoption->min = min_val;
    newoption->max = max_val;

    add_reloption((relopt_gen *) newoption);
}

/*
 * add_real_reloption
 *      Add a new float reloption
 */
void
add_real_reloption(bits32 kinds, const char *name, const char *desc, double default_val,
                   double min_val, double max_val)
{
    relopt_real *newoption;

    newoption = (relopt_real *) allocate_reloption(kinds, RELOPT_TYPE_REAL,
                                                   name, desc);
    newoption->default_val = default_val;
    newoption->min = min_val;
    newoption->max = max_val;

    add_reloption((relopt_gen *) newoption);
}

/*
 * add_string_reloption
 *      Add a new string reloption
 *
 * "validator" is an optional function pointer that can be used to test the
 * validity of the values.  It must elog(ERROR) when the argument string is
 * not acceptable for the variable.  Note that the default value must pass
 * the validation.
 */
void
add_string_reloption(bits32 kinds, const char *name, const char *desc, const char *default_val,
                     validate_string_relopt validator)
{
    relopt_string *newoption;

    /* make sure the validator/default combination is sane */
    if (validator)
        (validator) (default_val);

    newoption = (relopt_string *) allocate_reloption(kinds, RELOPT_TYPE_STRING,
                                                     name, desc);
    newoption->validate_cb = validator;
    if (default_val)
    {
        newoption->default_val = MemoryContextStrdup(TopMemoryContext,
                                                     default_val);
        newoption->default_len = strlen(default_val);
        newoption->default_isnull = false;
    }
    else
    {
        newoption->default_val = "";
        newoption->default_len = 0;
        newoption->default_isnull = true;
    }

    add_reloption((relopt_gen *) newoption);
}

/*
 * Transform a relation options list (list of DefElem) into the text array
 * format that is kept in pg_class.reloptions, including only those options
 * that are in the passed namespace.  The output values do not include the
 * namespace.
 *
 * This is used for three cases: CREATE TABLE/INDEX, ALTER TABLE SET, and
 * ALTER TABLE RESET.  In the ALTER cases, oldOptions is the existing
 * reloptions value (possibly NULL), and we replace or remove entries
 * as needed.
 *
 * If acceptOidsOff is true, then we allow oids = false, but throw error when
 * on. This is solely needed for backwards compatibility.
 *
 * Note that this is not responsible for determining whether the options
 * are valid, but it does check that namespaces for all the options given are
 * listed in validnsps.  The NULL namespace is always valid and need not be
 * explicitly listed.  Passing a NULL pointer means that only the NULL
 * namespace is valid.
 *
 * Both oldOptions and the result are text arrays (or NULL for "default"),
 * but we declare them as Datums to avoid including array.h in reloptions.h.
 */
Datum
transformRelOptions(Datum oldOptions, List *defList, const char *namspace,
                    char *validnsps[], bool acceptOidsOff, bool isReset)
{
    Datum       result;
    ArrayBuildState *astate;
    ListCell   *cell;

    /* no change if empty list */
    if (defList == NIL)
        return oldOptions;

    /* We build new array using accumArrayResult */
    astate = NULL;

    /* Copy any oldOptions that aren't to be replaced */
    if (PointerIsValid(DatumGetPointer(oldOptions)))
    {
        ArrayType  *array = DatumGetArrayTypeP(oldOptions);
        Datum      *oldoptions;
        int         noldoptions;
        int         i;

        deconstruct_array(array, TEXTOID, -1, false, 'i',
                          &oldoptions, NULL, &noldoptions);

        for (i = 0; i < noldoptions; i++)
        {
            char       *text_str = VARDATA(oldoptions[i]);
            int         text_len = VARSIZE(oldoptions[i]) - VARHDRSZ;

            /* Search for a match in defList */
            foreach(cell, defList)
            {
                DefElem    *def = (DefElem *) lfirst(cell);
                int         kw_len;

                /* ignore if not in the same namespace */
                if (namspace == NULL)
                {
                    if (def->defnamespace != NULL)
                        continue;
                }
                else if (def->defnamespace == NULL)
                    continue;
                else if (strcmp(def->defnamespace, namspace) != 0)
                    continue;

                kw_len = strlen(def->defname);
                if (text_len > kw_len && text_str[kw_len] == '=' &&
                    strncmp(text_str, def->defname, kw_len) == 0)
                    break;
            }
            if (!cell)
            {
                /* No match, so keep old option */
                astate = accumArrayResult(astate, oldoptions[i],
                                          false, TEXTOID,
                                          CurrentMemoryContext);
            }
        }
    }

    /*
     * If CREATE/SET, add new options to array; if RESET, just check that the
     * user didn't say RESET (option=val).  (Must do this because the grammar
     * doesn't enforce it.)
     */
    foreach(cell, defList)
    {
        DefElem    *def = (DefElem *) lfirst(cell);

        if (isReset)
        {
            if (def->arg != NULL)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("RESET must not include values for parameters")));
        }
        else
        {
            text       *t;
            const char *value;
            Size        len;

            /*
             * Error out if the namespace is not valid.  A NULL namespace is
             * always valid.
             */
            if (def->defnamespace != NULL)
            {
                bool        valid = false;
                int         i;

                if (validnsps)
                {
                    for (i = 0; validnsps[i]; i++)
                    {
                        if (strcmp(def->defnamespace, validnsps[i]) == 0)
                        {
                            valid = true;
                            break;
                        }
                    }
                }

                if (!valid)
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("unrecognized parameter namespace \"%s\"",
                                    def->defnamespace)));
            }

            /* ignore if not in the same namespace */
            if (namspace == NULL)
            {
                if (def->defnamespace != NULL)
                    continue;
            }
            else if (def->defnamespace == NULL)
                continue;
            else if (strcmp(def->defnamespace, namspace) != 0)
                continue;

            /*
             * Flatten the DefElem into a text string like "name=arg". If we
             * have just "name", assume "name=true" is meant.  Note: the
             * namespace is not output.
             */
            if (def->arg != NULL)
                value = defGetString(def);
            else
                value = "true";

            /*
             * This is not a great place for this test, but there's no other
             * convenient place to filter the option out. As WITH (oids =
             * false) will be removed someday, this seems like an acceptable
             * amount of ugly.
             */
            if (acceptOidsOff && def->defnamespace == NULL &&
                strcmp(def->defname, "oids") == 0)
            {
                if (defGetBoolean(def))
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("tables declared WITH OIDS are not supported")));
                /* skip over option, reloptions machinery doesn't know it */
                continue;
            }

            len = VARHDRSZ + strlen(def->defname) + 1 + strlen(value);
            /* +1 leaves room for sprintf's trailing null */
            t = (text *) palloc(len + 1);
            SET_VARSIZE(t, len);
            sprintf(VARDATA(t), "%s=%s", def->defname, value);

            astate = accumArrayResult(astate, PointerGetDatum(t),
                                      false, TEXTOID,
                                      CurrentMemoryContext);
        }
    }

    if (astate)
        result = makeArrayResult(astate, CurrentMemoryContext);
    else
        result = (Datum) 0;

    return result;
}


/*
 * Convert the text-array format of reloptions into a List of DefElem.
 * This is the inverse of transformRelOptions().
 */
List *
untransformRelOptions(Datum options)
{
    List       *result = NIL;
    ArrayType  *array;
    Datum      *optiondatums;
    int         noptions;
    int         i;

    /* Nothing to do if no options */
    if (!PointerIsValid(DatumGetPointer(options)))
        return result;

    array = DatumGetArrayTypeP(options);

    deconstruct_array(array, TEXTOID, -1, false, 'i',
                      &optiondatums, NULL, &noptions);

    for (i = 0; i < noptions; i++)
    {
        char       *s;
        char       *p;
        Node       *val = NULL;

        s = TextDatumGetCString(optiondatums[i]);
        p = strchr(s, '=');
        if (p)
        {
            *p++ = '\0';
            val = (Node *) makeString(pstrdup(p));
        }
        result = lappend(result, makeDefElem(pstrdup(s), val, -1));
    }

    return result;
}

/*
 * Extract and parse reloptions from a pg_class tuple.
 *
 * This is a low-level routine, expected to be used by relcache code and
 * callers that do not have a table's relcache entry (e.g. autovacuum).  For
 * other uses, consider grabbing the rd_options pointer from the relcache entry
 * instead.
 *
 * tupdesc is pg_class' tuple descriptor.  amoptions is a pointer to the index
 * AM's options parser function in the case of a tuple corresponding to an
 * index, or NULL otherwise.
 */
bytea *
extractRelOptions(HeapTuple tuple, TupleDesc tupdesc,
                  amoptions_function amoptions)
{
    bytea      *options;
    bool        isnull;
    Datum       datum;
    Form_pg_class classForm;

    datum = fastgetattr(tuple,
                        Anum_pg_class_reloptions,
                        tupdesc,
                        &isnull);
    if (isnull)
        return NULL;

    classForm = (Form_pg_class) GETSTRUCT(tuple);

    /* Parse into appropriate format; don't error out here */
    switch (classForm->relkind)
    {
        case RELKIND_RELATION:
        case RELKIND_TOASTVALUE:
        case RELKIND_MATVIEW:
        case RELKIND_PARTITIONED_TABLE:
            options = heap_reloptions(classForm->relkind, datum, false);
            break;
        case RELKIND_VIEW:
            options = view_reloptions(datum, false);
            break;
        case RELKIND_INDEX:
        case RELKIND_PARTITIONED_INDEX:
            options = index_reloptions(amoptions, datum, false);
            break;
        case RELKIND_FOREIGN_TABLE:
            options = NULL;
            break;
        default:
            Assert(false);      /* can't get here */
            options = NULL;     /* keep compiler quiet */
            break;
    }

    return options;
}

/*
 * Interpret reloptions that are given in text-array format.
 *
 * options is a reloption text array as constructed by transformRelOptions.
 * kind specifies the family of options to be processed.
 *
 * The return value is a relopt_value * array on which the options actually
 * set in the options array are marked with isset=true.  The length of this
 * array is returned in *numrelopts.  Options not set are also present in the
 * array; this is so that the caller can easily locate the default values.
 *
 * If there are no options of the given kind, numrelopts is set to 0 and NULL
 * is returned (unless options are illegally supplied despite none being
 * defined, in which case an error occurs).
 *
 * Note: values of type int, bool and real are allocated as part of the
 * returned array.  Values of type string are allocated separately and must
 * be freed by the caller.
 */
relopt_value *
parseRelOptions(Datum options, bool validate, relopt_kind kind,
                int *numrelopts)
{
    relopt_value *reloptions = NULL;
    int         numoptions = 0;
    int         i;
    int         j;

    if (need_initialization)
        initialize_reloptions();

    /* Build a list of expected options, based on kind */

    for (i = 0; relOpts[i]; i++)
        if (relOpts[i]->kinds & kind)
            numoptions++;

    if (numoptions > 0)
    {
        reloptions = palloc(numoptions * sizeof(relopt_value));

        for (i = 0, j = 0; relOpts[i]; i++)
        {
            if (relOpts[i]->kinds & kind)
            {
                reloptions[j].gen = relOpts[i];
                reloptions[j].isset = false;
                j++;
            }
        }
    }

    /* Done if no options */
    if (PointerIsValid(DatumGetPointer(options)))
    {
        ArrayType  *array = DatumGetArrayTypeP(options);
        Datum      *optiondatums;
        int         noptions;

        deconstruct_array(array, TEXTOID, -1, false, 'i',
                          &optiondatums, NULL, &noptions);

        for (i = 0; i < noptions; i++)
        {
            char       *text_str = VARDATA(optiondatums[i]);
            int         text_len = VARSIZE(optiondatums[i]) - VARHDRSZ;
            int         j;

            /* Search for a match in reloptions */
            for (j = 0; j < numoptions; j++)
            {
                int         kw_len = reloptions[j].gen->namelen;

                if (text_len > kw_len && text_str[kw_len] == '=' &&
                    strncmp(text_str, reloptions[j].gen->name, kw_len) == 0)
                {
                    parse_one_reloption(&reloptions[j], text_str, text_len,
                                        validate);
                    break;
                }
            }

            if (j >= numoptions && validate)
            {
                char       *s;
                char       *p;

                s = TextDatumGetCString(optiondatums[i]);
                p = strchr(s, '=');
                if (p)
                    *p = '\0';
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("unrecognized parameter \"%s\"", s)));
            }
        }

        /* It's worth avoiding memory leaks in this function */
        pfree(optiondatums);
        if (((void *) array) != DatumGetPointer(options))
            pfree(array);
    }

    *numrelopts = numoptions;
    return reloptions;
}

/*
 * Subroutine for parseRelOptions, to parse and validate a single option's
 * value
 */
static void
parse_one_reloption(relopt_value *option, char *text_str, int text_len,
                    bool validate)
{
    char       *value;
    int         value_len;
    bool        parsed;
    bool        nofree = false;

    if (option->isset && validate)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("parameter \"%s\" specified more than once",
                        option->gen->name)));

    value_len = text_len - option->gen->namelen - 1;
    value = (char *) palloc(value_len + 1);
    memcpy(value, text_str + option->gen->namelen + 1, value_len);
    value[value_len] = '\0';

    switch (option->gen->type)
    {
        case RELOPT_TYPE_BOOL:
            {
                parsed = parse_bool(value, &option->values.bool_val);
                if (validate && !parsed)
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("invalid value for boolean option \"%s\": %s",
                                    option->gen->name, value)));
            }
            break;
        case RELOPT_TYPE_INT:
            {
                relopt_int *optint = (relopt_int *) option->gen;

                parsed = parse_int(value, &option->values.int_val, 0, NULL);
                if (validate && !parsed)
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("invalid value for integer option \"%s\": %s",
                                    option->gen->name, value)));
                if (validate && (option->values.int_val < optint->min ||
                                 option->values.int_val > optint->max))
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("value %s out of bounds for option \"%s\"",
                                    value, option->gen->name),
                             errdetail("Valid values are between \"%d\" and \"%d\".",
                                       optint->min, optint->max)));
            }
            break;
        case RELOPT_TYPE_REAL:
            {
                relopt_real *optreal = (relopt_real *) option->gen;

                parsed = parse_real(value, &option->values.real_val, 0, NULL);
                if (validate && !parsed)
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("invalid value for floating point option \"%s\": %s",
                                    option->gen->name, value)));
                if (validate && (option->values.real_val < optreal->min ||
                                 option->values.real_val > optreal->max))
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("value %s out of bounds for option \"%s\"",
                                    value, option->gen->name),
                             errdetail("Valid values are between \"%f\" and \"%f\".",
                                       optreal->min, optreal->max)));
            }
            break;
        case RELOPT_TYPE_STRING:
            {
                relopt_string *optstring = (relopt_string *) option->gen;

                option->values.string_val = value;
                nofree = true;
                if (validate && optstring->validate_cb)
                    (optstring->validate_cb) (value);
                parsed = true;
            }
            break;
        default:
            elog(ERROR, "unsupported reloption type %d", option->gen->type);
            parsed = true;      /* quiet compiler */
            break;
    }

    if (parsed)
        option->isset = true;
    if (!nofree)
        pfree(value);
}

/*
 * Given the result from parseRelOptions, allocate a struct that's of the
 * specified base size plus any extra space that's needed for string variables.
 *
 * "base" should be sizeof(struct) of the reloptions struct (StdRdOptions or
 * equivalent).
 */
void *
allocateReloptStruct(Size base, relopt_value *options, int numoptions)
{
    Size        size = base;
    int         i;

    for (i = 0; i < numoptions; i++)
        if (options[i].gen->type == RELOPT_TYPE_STRING)
            size += GET_STRING_RELOPTION_LEN(options[i]) + 1;

    return palloc0(size);
}

/*
 * Given the result of parseRelOptions and a parsing table, fill in the
 * struct (previously allocated with allocateReloptStruct) with the parsed
 * values.
 *
 * rdopts is the pointer to the allocated struct to be filled.
 * basesize is the sizeof(struct) that was passed to allocateReloptStruct.
 * options, of length numoptions, is parseRelOptions' output.
 * elems, of length numelems, is the table describing the allowed options.
 * When validate is true, it is expected that all options appear in elems.
 */
void
fillRelOptions(void *rdopts, Size basesize,
               relopt_value *options, int numoptions,
               bool validate,
               const relopt_parse_elt *elems, int numelems)
{
    int         i;
    int         offset = basesize;

    for (i = 0; i < numoptions; i++)
    {
        int         j;
        bool        found = false;

        for (j = 0; j < numelems; j++)
        {
            if (strcmp(options[i].gen->name, elems[j].optname) == 0)
            {
                relopt_string *optstring;
                char       *itempos = ((char *) rdopts) + elems[j].offset;
                char       *string_val;

                switch (options[i].gen->type)
                {
                    case RELOPT_TYPE_BOOL:
                        *(bool *) itempos = options[i].isset ?
                            options[i].values.bool_val :
                            ((relopt_bool *) options[i].gen)->default_val;
                        break;
                    case RELOPT_TYPE_INT:
                        *(int *) itempos = options[i].isset ?
                            options[i].values.int_val :
                            ((relopt_int *) options[i].gen)->default_val;
                        break;
                    case RELOPT_TYPE_REAL:
                        *(double *) itempos = options[i].isset ?
                            options[i].values.real_val :
                            ((relopt_real *) options[i].gen)->default_val;
                        break;
                    case RELOPT_TYPE_STRING:
                        optstring = (relopt_string *) options[i].gen;
                        if (options[i].isset)
                            string_val = options[i].values.string_val;
                        else if (!optstring->default_isnull)
                            string_val = optstring->default_val;
                        else
                            string_val = NULL;

                        if (string_val == NULL)
                            *(int *) itempos = 0;
                        else
                        {
                            strcpy((char *) rdopts + offset, string_val);
                            *(int *) itempos = offset;
                            offset += strlen(string_val) + 1;
                        }
                        break;
                    default:
                        elog(ERROR, "unsupported reloption type %d",
                             options[i].gen->type);
                        break;
                }
                found = true;
                break;
            }
        }
        if (validate && !found)
            elog(ERROR, "reloption \"%s\" not found in parse table",
                 options[i].gen->name);
    }
    SET_VARSIZE(rdopts, offset);
}


/*
 * Option parser for anything that uses StdRdOptions.
 */
bytea *
default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
{
    relopt_value *options;
    StdRdOptions *rdopts;
    int         numoptions;
    static const relopt_parse_elt tab[] = {
        {"fillfactor", RELOPT_TYPE_INT, offsetof(StdRdOptions, fillfactor)},
        {"autovacuum_enabled", RELOPT_TYPE_BOOL,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, enabled)},
        {"autovacuum_vacuum_threshold", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, vacuum_threshold)},
        {"autovacuum_analyze_threshold", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, analyze_threshold)},
        {"autovacuum_vacuum_cost_limit", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, vacuum_cost_limit)},
        {"autovacuum_freeze_min_age", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, freeze_min_age)},
        {"autovacuum_freeze_max_age", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, freeze_max_age)},
        {"autovacuum_freeze_table_age", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, freeze_table_age)},
        {"autovacuum_multixact_freeze_min_age", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, multixact_freeze_min_age)},
        {"autovacuum_multixact_freeze_max_age", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, multixact_freeze_max_age)},
        {"autovacuum_multixact_freeze_table_age", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, multixact_freeze_table_age)},
        {"log_autovacuum_min_duration", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, log_min_duration)},
        {"toast_tuple_target", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, toast_tuple_target)},
        {"autovacuum_vacuum_cost_delay", RELOPT_TYPE_REAL,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, vacuum_cost_delay)},
        {"autovacuum_vacuum_scale_factor", RELOPT_TYPE_REAL,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, vacuum_scale_factor)},
        {"autovacuum_analyze_scale_factor", RELOPT_TYPE_REAL,
        offsetof(StdRdOptions, autovacuum) + offsetof(AutoVacOpts, analyze_scale_factor)},
        {"user_catalog_table", RELOPT_TYPE_BOOL,
        offsetof(StdRdOptions, user_catalog_table)},
        {"parallel_workers", RELOPT_TYPE_INT,
        offsetof(StdRdOptions, parallel_workers)},
        {"vacuum_cleanup_index_scale_factor", RELOPT_TYPE_REAL,
        offsetof(StdRdOptions, vacuum_cleanup_index_scale_factor)},
        {"vacuum_index_cleanup", RELOPT_TYPE_BOOL,
        offsetof(StdRdOptions, vacuum_index_cleanup)},
        {"vacuum_truncate", RELOPT_TYPE_BOOL,
        offsetof(StdRdOptions, vacuum_truncate)}
    };

    options = parseRelOptions(reloptions, validate, kind, &numoptions);

    /* if none set, we're done */
    if (numoptions == 0)
        return NULL;

    rdopts = allocateReloptStruct(sizeof(StdRdOptions), options, numoptions);

    fillRelOptions((void *) rdopts, sizeof(StdRdOptions), options, numoptions,
                   validate, tab, lengthof(tab));

    pfree(options);

    return (bytea *) rdopts;
}

/*
 * Option parser for views
 */
bytea *
view_reloptions(Datum reloptions, bool validate)
{
    relopt_value *options;
    ViewOptions *vopts;
    int         numoptions;
    static const relopt_parse_elt tab[] = {
        {"security_barrier", RELOPT_TYPE_BOOL,
        offsetof(ViewOptions, security_barrier)},
        {"check_option", RELOPT_TYPE_STRING,
        offsetof(ViewOptions, check_option_offset)}
    };

    options = parseRelOptions(reloptions, validate, RELOPT_KIND_VIEW, &numoptions);

    /* if none set, we're done */
    if (numoptions == 0)
        return NULL;

    vopts = allocateReloptStruct(sizeof(ViewOptions), options, numoptions);

    fillRelOptions((void *) vopts, sizeof(ViewOptions), options, numoptions,
                   validate, tab, lengthof(tab));

    pfree(options);

    return (bytea *) vopts;
}

/*
 * Parse options for heaps, views and toast tables.
 */
bytea *
heap_reloptions(char relkind, Datum reloptions, bool validate)
{
    StdRdOptions *rdopts;

    switch (relkind)
    {
        case RELKIND_TOASTVALUE:
            rdopts = (StdRdOptions *)
                default_reloptions(reloptions, validate, RELOPT_KIND_TOAST);
            if (rdopts != NULL)
            {
                /* adjust default-only parameters for TOAST relations */
                rdopts->fillfactor = 100;
                rdopts->autovacuum.analyze_threshold = -1;
                rdopts->autovacuum.analyze_scale_factor = -1;
            }
            return (bytea *) rdopts;
        case RELKIND_RELATION:
        case RELKIND_MATVIEW:
            return default_reloptions(reloptions, validate, RELOPT_KIND_HEAP);
        case RELKIND_PARTITIONED_TABLE:
            return default_reloptions(reloptions, validate,
                                      RELOPT_KIND_PARTITIONED);
        default:
            /* other relkinds are not supported */
            return NULL;
    }
}


/*
 * Parse options for indexes.
 *
 *  amoptions   index AM's option parser function
 *  reloptions  options as text[] datum
 *  validate    error flag
 */
bytea *
index_reloptions(amoptions_function amoptions, Datum reloptions, bool validate)
{
    Assert(amoptions != NULL);

    /* Assume function is strict */
    if (!PointerIsValid(DatumGetPointer(reloptions)))
        return NULL;

    return amoptions(reloptions, validate);
}

/*
 * Option parser for attribute reloptions
 */
bytea *
attribute_reloptions(Datum reloptions, bool validate)
{
    relopt_value *options;
    AttributeOpts *aopts;
    int         numoptions;
    static const relopt_parse_elt tab[] = {
        {"n_distinct", RELOPT_TYPE_REAL, offsetof(AttributeOpts, n_distinct)},
        {"n_distinct_inherited", RELOPT_TYPE_REAL, offsetof(AttributeOpts, n_distinct_inherited)}
    };

    options = parseRelOptions(reloptions, validate, RELOPT_KIND_ATTRIBUTE,
                              &numoptions);

    /* if none set, we're done */
    if (numoptions == 0)
        return NULL;

    aopts = allocateReloptStruct(sizeof(AttributeOpts), options, numoptions);

    fillRelOptions((void *) aopts, sizeof(AttributeOpts), options, numoptions,
                   validate, tab, lengthof(tab));

    pfree(options);

    return (bytea *) aopts;
}

/*
 * Option parser for tablespace reloptions
 */
bytea *
tablespace_reloptions(Datum reloptions, bool validate)
{
    relopt_value *options;
    TableSpaceOpts *tsopts;
    int         numoptions;
    static const relopt_parse_elt tab[] = {
        {"random_page_cost", RELOPT_TYPE_REAL, offsetof(TableSpaceOpts, random_page_cost)},
        {"seq_page_cost", RELOPT_TYPE_REAL, offsetof(TableSpaceOpts, seq_page_cost)},
        {"effective_io_concurrency", RELOPT_TYPE_INT, offsetof(TableSpaceOpts, effective_io_concurrency)}
    };

    options = parseRelOptions(reloptions, validate, RELOPT_KIND_TABLESPACE,
                              &numoptions);

    /* if none set, we're done */
    if (numoptions == 0)
        return NULL;

    tsopts = allocateReloptStruct(sizeof(TableSpaceOpts), options, numoptions);

    fillRelOptions((void *) tsopts, sizeof(TableSpaceOpts), options, numoptions,
                   validate, tab, lengthof(tab));

    pfree(options);

    return (bytea *) tsopts;
}

/*
 * Determine the required LOCKMODE from an option list.
 *
 * Called from AlterTableGetLockLevel(), see that function
 * for a longer explanation of how this works.
 */
LOCKMODE
AlterTableGetRelOptionsLockLevel(List *defList)
{
    LOCKMODE    lockmode = NoLock;
    ListCell   *cell;

    if (defList == NIL)
        return AccessExclusiveLock;

    if (need_initialization)
        initialize_reloptions();

    foreach(cell, defList)
    {
        DefElem    *def = (DefElem *) lfirst(cell);
        int         i;

        for (i = 0; relOpts[i]; i++)
        {
            if (strncmp(relOpts[i]->name,
                        def->defname,
                        relOpts[i]->namelen + 1) == 0)
            {
                if (lockmode < relOpts[i]->lockmode)
                    lockmode = relOpts[i]->lockmode;
            }
        }
    }

    return lockmode;
}