test_decoding.c

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/*-------------------------------------------------------------------------
 *
 * test_decoding.c
 *        example logical decoding output plugin
 *
 * Copyright (c) 2012-2020, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *        contrib/test_decoding/test_decoding.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "catalog/pg_type.h"

#include "replication/logical.h"
#include "replication/origin.h"

#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"

PG_MODULE_MAGIC;

/* These must be available to dlsym() */
extern void _PG_init(void);
extern void _PG_output_plugin_init(OutputPluginCallbacks *cb);

typedef struct
{
    MemoryContext context;
    bool        include_xids;
    bool        include_timestamp;
    bool        skip_empty_xacts;
    bool        only_local;
} TestDecodingData;

/*
 * Maintain the per-transaction level variables to track whether the
 * transaction and or streams have written any changes. In streaming mode the
 * transaction can be decoded in streams so along with maintaining whether the
 * transaction has written any changes, we also need to track whether the
 * current stream has written any changes. This is required so that if user
 * has requested to skip the empty transactions we can skip the empty streams
 * even though the transaction has written some changes.
 */
typedef struct
{
    bool        xact_wrote_changes;
    bool        stream_wrote_changes;
} TestDecodingTxnData;

static void pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
                              bool is_init);
static void pg_decode_shutdown(LogicalDecodingContext *ctx);
static void pg_decode_begin_txn(LogicalDecodingContext *ctx,
                                ReorderBufferTXN *txn);
static void pg_output_begin(LogicalDecodingContext *ctx,
                            TestDecodingData *data,
                            ReorderBufferTXN *txn,
                            bool last_write);
static void pg_decode_commit_txn(LogicalDecodingContext *ctx,
                                 ReorderBufferTXN *txn, XLogRecPtr commit_lsn);
static void pg_decode_change(LogicalDecodingContext *ctx,
                             ReorderBufferTXN *txn, Relation rel,
                             ReorderBufferChange *change);
static void pg_decode_truncate(LogicalDecodingContext *ctx,
                               ReorderBufferTXN *txn,
                               int nrelations, Relation relations[],
                               ReorderBufferChange *change);
static bool pg_decode_filter(LogicalDecodingContext *ctx,
                             RepOriginId origin_id);
static void pg_decode_message(LogicalDecodingContext *ctx,
                              ReorderBufferTXN *txn, XLogRecPtr message_lsn,
                              bool transactional, const char *prefix,
                              Size sz, const char *message);
static void pg_decode_stream_start(LogicalDecodingContext *ctx,
                                   ReorderBufferTXN *txn);
static void pg_output_stream_start(LogicalDecodingContext *ctx,
                                   TestDecodingData *data,
                                   ReorderBufferTXN *txn,
                                   bool last_write);
static void pg_decode_stream_stop(LogicalDecodingContext *ctx,
                                  ReorderBufferTXN *txn);
static void pg_decode_stream_abort(LogicalDecodingContext *ctx,
                                   ReorderBufferTXN *txn,
                                   XLogRecPtr abort_lsn);
static void pg_decode_stream_commit(LogicalDecodingContext *ctx,
                                    ReorderBufferTXN *txn,
                                    XLogRecPtr commit_lsn);
static void pg_decode_stream_change(LogicalDecodingContext *ctx,
                                    ReorderBufferTXN *txn,
                                    Relation relation,
                                    ReorderBufferChange *change);
static void pg_decode_stream_message(LogicalDecodingContext *ctx,
                                     ReorderBufferTXN *txn, XLogRecPtr message_lsn,
                                     bool transactional, const char *prefix,
                                     Size sz, const char *message);
static void pg_decode_stream_truncate(LogicalDecodingContext *ctx,
                                      ReorderBufferTXN *txn,
                                      int nrelations, Relation relations[],
                                      ReorderBufferChange *change);

void
_PG_init(void)
{
    /* other plugins can perform things here */
}

/* specify output plugin callbacks */
void
_PG_output_plugin_init(OutputPluginCallbacks *cb)
{
    AssertVariableIsOfType(&_PG_output_plugin_init, LogicalOutputPluginInit);

    cb->startup_cb = pg_decode_startup;
    cb->begin_cb = pg_decode_begin_txn;
    cb->change_cb = pg_decode_change;
    cb->truncate_cb = pg_decode_truncate;
    cb->commit_cb = pg_decode_commit_txn;
    cb->filter_by_origin_cb = pg_decode_filter;
    cb->shutdown_cb = pg_decode_shutdown;
    cb->message_cb = pg_decode_message;
    cb->stream_start_cb = pg_decode_stream_start;
    cb->stream_stop_cb = pg_decode_stream_stop;
    cb->stream_abort_cb = pg_decode_stream_abort;
    cb->stream_commit_cb = pg_decode_stream_commit;
    cb->stream_change_cb = pg_decode_stream_change;
    cb->stream_message_cb = pg_decode_stream_message;
    cb->stream_truncate_cb = pg_decode_stream_truncate;
}


/* initialize this plugin */
static void
pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
                  bool is_init)
{
    ListCell   *option;
    TestDecodingData *data;
    bool        enable_streaming = false;

    data = palloc0(sizeof(TestDecodingData));
    data->context = AllocSetContextCreate(ctx->context,
                                          "text conversion context",
                                          ALLOCSET_DEFAULT_SIZES);
    data->include_xids = true;
    data->include_timestamp = false;
    data->skip_empty_xacts = false;
    data->only_local = false;

    ctx->output_plugin_private = data;

    opt->output_type = OUTPUT_PLUGIN_TEXTUAL_OUTPUT;
    opt->receive_rewrites = false;

    foreach(option, ctx->output_plugin_options)
    {
        DefElem    *elem = lfirst(option);

        Assert(elem->arg == NULL || IsA(elem->arg, String));

        if (strcmp(elem->defname, "include-xids") == 0)
        {
            /* if option does not provide a value, it means its value is true */
            if (elem->arg == NULL)
                data->include_xids = true;
            else if (!parse_bool(strVal(elem->arg), &data->include_xids))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse value \"%s\" for parameter \"%s\"",
                                strVal(elem->arg), elem->defname)));
        }
        else if (strcmp(elem->defname, "include-timestamp") == 0)
        {
            if (elem->arg == NULL)
                data->include_timestamp = true;
            else if (!parse_bool(strVal(elem->arg), &data->include_timestamp))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse value \"%s\" for parameter \"%s\"",
                                strVal(elem->arg), elem->defname)));
        }
        else if (strcmp(elem->defname, "force-binary") == 0)
        {
            bool        force_binary;

            if (elem->arg == NULL)
                continue;
            else if (!parse_bool(strVal(elem->arg), &force_binary))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse value \"%s\" for parameter \"%s\"",
                                strVal(elem->arg), elem->defname)));

            if (force_binary)
                opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT;
        }
        else if (strcmp(elem->defname, "skip-empty-xacts") == 0)
        {

            if (elem->arg == NULL)
                data->skip_empty_xacts = true;
            else if (!parse_bool(strVal(elem->arg), &data->skip_empty_xacts))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse value \"%s\" for parameter \"%s\"",
                                strVal(elem->arg), elem->defname)));
        }
        else if (strcmp(elem->defname, "only-local") == 0)
        {

            if (elem->arg == NULL)
                data->only_local = true;
            else if (!parse_bool(strVal(elem->arg), &data->only_local))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse value \"%s\" for parameter \"%s\"",
                                strVal(elem->arg), elem->defname)));
        }
        else if (strcmp(elem->defname, "include-rewrites") == 0)
        {

            if (elem->arg == NULL)
                continue;
            else if (!parse_bool(strVal(elem->arg), &opt->receive_rewrites))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse value \"%s\" for parameter \"%s\"",
                                strVal(elem->arg), elem->defname)));
        }
        else if (strcmp(elem->defname, "stream-changes") == 0)
        {
            if (elem->arg == NULL)
                continue;
            else if (!parse_bool(strVal(elem->arg), &enable_streaming))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse value \"%s\" for parameter \"%s\"",
                                strVal(elem->arg), elem->defname)));
        }
        else
        {
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("option \"%s\" = \"%s\" is unknown",
                            elem->defname,
                            elem->arg ? strVal(elem->arg) : "(null)")));
        }
    }

    ctx->streaming &= enable_streaming;
}

/* cleanup this plugin's resources */
static void
pg_decode_shutdown(LogicalDecodingContext *ctx)
{
    TestDecodingData *data = ctx->output_plugin_private;

    /* cleanup our own resources via memory context reset */
    MemoryContextDelete(data->context);
}

/* BEGIN callback */
static void
pg_decode_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
{
    TestDecodingData *data = ctx->output_plugin_private;
    TestDecodingTxnData *txndata =
    MemoryContextAllocZero(ctx->context, sizeof(TestDecodingTxnData));

    txndata->xact_wrote_changes = false;
    txn->output_plugin_private = txndata;

    if (data->skip_empty_xacts)
        return;

    pg_output_begin(ctx, data, txn, true);
}

static void
pg_output_begin(LogicalDecodingContext *ctx, TestDecodingData *data, ReorderBufferTXN *txn, bool last_write)
{
    OutputPluginPrepareWrite(ctx, last_write);
    if (data->include_xids)
        appendStringInfo(ctx->out, "BEGIN %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "BEGIN");
    OutputPluginWrite(ctx, last_write);
}

/* COMMIT callback */
static void
pg_decode_commit_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
                     XLogRecPtr commit_lsn)
{
    TestDecodingData *data = ctx->output_plugin_private;
    TestDecodingTxnData *txndata = txn->output_plugin_private;
    bool        xact_wrote_changes = txndata->xact_wrote_changes;

    pfree(txndata);
    txn->output_plugin_private = NULL;

    if (data->skip_empty_xacts && !xact_wrote_changes)
        return;

    OutputPluginPrepareWrite(ctx, true);
    if (data->include_xids)
        appendStringInfo(ctx->out, "COMMIT %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "COMMIT");

    if (data->include_timestamp)
        appendStringInfo(ctx->out, " (at %s)",
                         timestamptz_to_str(txn->commit_time));

    OutputPluginWrite(ctx, true);
}

static bool
pg_decode_filter(LogicalDecodingContext *ctx,
                 RepOriginId origin_id)
{
    TestDecodingData *data = ctx->output_plugin_private;

    if (data->only_local && origin_id != InvalidRepOriginId)
        return true;
    return false;
}

/*
 * Print literal `outputstr' already represented as string of type `typid'
 * into stringbuf `s'.
 *
 * Some builtin types aren't quoted, the rest is quoted. Escaping is done as
 * if standard_conforming_strings were enabled.
 */
static void
print_literal(StringInfo s, Oid typid, char *outputstr)
{
    const char *valptr;

    switch (typid)
    {
        case INT2OID:
        case INT4OID:
        case INT8OID:
        case OIDOID:
        case FLOAT4OID:
        case FLOAT8OID:
        case NUMERICOID:
            /* NB: We don't care about Inf, NaN et al. */
            appendStringInfoString(s, outputstr);
            break;

        case BITOID:
        case VARBITOID:
            appendStringInfo(s, "B'%s'", outputstr);
            break;

        case BOOLOID:
            if (strcmp(outputstr, "t") == 0)
                appendStringInfoString(s, "true");
            else
                appendStringInfoString(s, "false");
            break;

        default:
            appendStringInfoChar(s, '\'');
            for (valptr = outputstr; *valptr; valptr++)
            {
                char        ch = *valptr;

                if (SQL_STR_DOUBLE(ch, false))
                    appendStringInfoChar(s, ch);
                appendStringInfoChar(s, ch);
            }
            appendStringInfoChar(s, '\'');
            break;
    }
}

/* print the tuple 'tuple' into the StringInfo s */
static void
tuple_to_stringinfo(StringInfo s, TupleDesc tupdesc, HeapTuple tuple, bool skip_nulls)
{
    int         natt;

    /* print all columns individually */
    for (natt = 0; natt < tupdesc->natts; natt++)
    {
        Form_pg_attribute attr; /* the attribute itself */
        Oid         typid;      /* type of current attribute */
        Oid         typoutput;  /* output function */
        bool        typisvarlena;
        Datum       origval;    /* possibly toasted Datum */
        bool        isnull;     /* column is null? */

        attr = TupleDescAttr(tupdesc, natt);

        /*
         * don't print dropped columns, we can't be sure everything is
         * available for them
         */
        if (attr->attisdropped)
            continue;

        /*
         * Don't print system columns, oid will already have been printed if
         * present.
         */
        if (attr->attnum < 0)
            continue;

        typid = attr->atttypid;

        /* get Datum from tuple */
        origval = heap_getattr(tuple, natt + 1, tupdesc, &isnull);

        if (isnull && skip_nulls)
            continue;

        /* print attribute name */
        appendStringInfoChar(s, ' ');
        appendStringInfoString(s, quote_identifier(NameStr(attr->attname)));

        /* print attribute type */
        appendStringInfoChar(s, '[');
        appendStringInfoString(s, format_type_be(typid));
        appendStringInfoChar(s, ']');

        /* query output function */
        getTypeOutputInfo(typid,
                          &typoutput, &typisvarlena);

        /* print separator */
        appendStringInfoChar(s, ':');

        /* print data */
        if (isnull)
            appendStringInfoString(s, "null");
        else if (typisvarlena && VARATT_IS_EXTERNAL_ONDISK(origval))
            appendStringInfoString(s, "unchanged-toast-datum");
        else if (!typisvarlena)
            print_literal(s, typid,
                          OidOutputFunctionCall(typoutput, origval));
        else
        {
            Datum       val;    /* definitely detoasted Datum */

            val = PointerGetDatum(PG_DETOAST_DATUM(origval));
            print_literal(s, typid, OidOutputFunctionCall(typoutput, val));
        }
    }
}

/*
 * callback for individual changed tuples
 */
static void
pg_decode_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
                 Relation relation, ReorderBufferChange *change)
{
    TestDecodingData *data;
    TestDecodingTxnData *txndata;
    Form_pg_class class_form;
    TupleDesc   tupdesc;
    MemoryContext old;

    data = ctx->output_plugin_private;
    txndata = txn->output_plugin_private;

    /* output BEGIN if we haven't yet */
    if (data->skip_empty_xacts && !txndata->xact_wrote_changes)
    {
        pg_output_begin(ctx, data, txn, false);
    }
    txndata->xact_wrote_changes = true;

    class_form = RelationGetForm(relation);
    tupdesc = RelationGetDescr(relation);

    /* Avoid leaking memory by using and resetting our own context */
    old = MemoryContextSwitchTo(data->context);

    OutputPluginPrepareWrite(ctx, true);

    appendStringInfoString(ctx->out, "table ");
    appendStringInfoString(ctx->out,
                           quote_qualified_identifier(get_namespace_name(get_rel_namespace(RelationGetRelid(relation))),
                                                      class_form->relrewrite ?
                                                      get_rel_name(class_form->relrewrite) :
                                                      NameStr(class_form->relname)));
    appendStringInfoChar(ctx->out, ':');

    switch (change->action)
    {
        case REORDER_BUFFER_CHANGE_INSERT:
            appendStringInfoString(ctx->out, " INSERT:");
            if (change->data.tp.newtuple == NULL)
                appendStringInfoString(ctx->out, " (no-tuple-data)");
            else
                tuple_to_stringinfo(ctx->out, tupdesc,
                                    &change->data.tp.newtuple->tuple,
                                    false);
            break;
        case REORDER_BUFFER_CHANGE_UPDATE:
            appendStringInfoString(ctx->out, " UPDATE:");
            if (change->data.tp.oldtuple != NULL)
            {
                appendStringInfoString(ctx->out, " old-key:");
                tuple_to_stringinfo(ctx->out, tupdesc,
                                    &change->data.tp.oldtuple->tuple,
                                    true);
                appendStringInfoString(ctx->out, " new-tuple:");
            }

            if (change->data.tp.newtuple == NULL)
                appendStringInfoString(ctx->out, " (no-tuple-data)");
            else
                tuple_to_stringinfo(ctx->out, tupdesc,
                                    &change->data.tp.newtuple->tuple,
                                    false);
            break;
        case REORDER_BUFFER_CHANGE_DELETE:
            appendStringInfoString(ctx->out, " DELETE:");

            /* if there was no PK, we only know that a delete happened */
            if (change->data.tp.oldtuple == NULL)
                appendStringInfoString(ctx->out, " (no-tuple-data)");
            /* In DELETE, only the replica identity is present; display that */
            else
                tuple_to_stringinfo(ctx->out, tupdesc,
                                    &change->data.tp.oldtuple->tuple,
                                    true);
            break;
        default:
            Assert(false);
    }

    MemoryContextSwitchTo(old);
    MemoryContextReset(data->context);

    OutputPluginWrite(ctx, true);
}

static void
pg_decode_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
                   int nrelations, Relation relations[], ReorderBufferChange *change)
{
    TestDecodingData *data;
    TestDecodingTxnData *txndata;
    MemoryContext old;
    int         i;

    data = ctx->output_plugin_private;
    txndata = txn->output_plugin_private;

    /* output BEGIN if we haven't yet */
    if (data->skip_empty_xacts && !txndata->xact_wrote_changes)
    {
        pg_output_begin(ctx, data, txn, false);
    }
    txndata->xact_wrote_changes = true;

    /* Avoid leaking memory by using and resetting our own context */
    old = MemoryContextSwitchTo(data->context);

    OutputPluginPrepareWrite(ctx, true);

    appendStringInfoString(ctx->out, "table ");

    for (i = 0; i < nrelations; i++)
    {
        if (i > 0)
            appendStringInfoString(ctx->out, ", ");

        appendStringInfoString(ctx->out,
                               quote_qualified_identifier(get_namespace_name(relations[i]->rd_rel->relnamespace),
                                                          NameStr(relations[i]->rd_rel->relname)));
    }

    appendStringInfoString(ctx->out, ": TRUNCATE:");

    if (change->data.truncate.restart_seqs
        || change->data.truncate.cascade)
    {
        if (change->data.truncate.restart_seqs)
            appendStringInfoString(ctx->out, " restart_seqs");
        if (change->data.truncate.cascade)
            appendStringInfoString(ctx->out, " cascade");
    }
    else
        appendStringInfoString(ctx->out, " (no-flags)");

    MemoryContextSwitchTo(old);
    MemoryContextReset(data->context);

    OutputPluginWrite(ctx, true);
}

static void
pg_decode_message(LogicalDecodingContext *ctx,
                  ReorderBufferTXN *txn, XLogRecPtr lsn, bool transactional,
                  const char *prefix, Size sz, const char *message)
{
    OutputPluginPrepareWrite(ctx, true);
    appendStringInfo(ctx->out, "message: transactional: %d prefix: %s, sz: %zu content:",
                     transactional, prefix, sz);
    appendBinaryStringInfo(ctx->out, message, sz);
    OutputPluginWrite(ctx, true);
}

static void
pg_decode_stream_start(LogicalDecodingContext *ctx,
                       ReorderBufferTXN *txn)
{
    TestDecodingData *data = ctx->output_plugin_private;
    TestDecodingTxnData *txndata = txn->output_plugin_private;

    /*
     * Allocate the txn plugin data for the first stream in the transaction.
     */
    if (txndata == NULL)
    {
        txndata =
            MemoryContextAllocZero(ctx->context, sizeof(TestDecodingTxnData));
        txndata->xact_wrote_changes = false;
        txn->output_plugin_private = txndata;
    }

    txndata->stream_wrote_changes = false;
    if (data->skip_empty_xacts)
        return;
    pg_output_stream_start(ctx, data, txn, true);
}

static void
pg_output_stream_start(LogicalDecodingContext *ctx, TestDecodingData *data, ReorderBufferTXN *txn, bool last_write)
{
    OutputPluginPrepareWrite(ctx, last_write);
    if (data->include_xids)
        appendStringInfo(ctx->out, "opening a streamed block for transaction TXN %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "opening a streamed block for transaction");
    OutputPluginWrite(ctx, last_write);
}

static void
pg_decode_stream_stop(LogicalDecodingContext *ctx,
                      ReorderBufferTXN *txn)
{
    TestDecodingData *data = ctx->output_plugin_private;
    TestDecodingTxnData *txndata = txn->output_plugin_private;

    if (data->skip_empty_xacts && !txndata->stream_wrote_changes)
        return;

    OutputPluginPrepareWrite(ctx, true);
    if (data->include_xids)
        appendStringInfo(ctx->out, "closing a streamed block for transaction TXN %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "closing a streamed block for transaction");
    OutputPluginWrite(ctx, true);
}

static void
pg_decode_stream_abort(LogicalDecodingContext *ctx,
                       ReorderBufferTXN *txn,
                       XLogRecPtr abort_lsn)
{
    TestDecodingData *data = ctx->output_plugin_private;

    /*
     * stream abort can be sent for an individual subtransaction but we
     * maintain the output_plugin_private only under the toptxn so if this is
     * not the toptxn then fetch the toptxn.
     */
    ReorderBufferTXN *toptxn = txn->toptxn ? txn->toptxn : txn;
    TestDecodingTxnData *txndata = toptxn->output_plugin_private;
    bool        xact_wrote_changes = txndata->xact_wrote_changes;

    if (txn->toptxn == NULL)
    {
        Assert(txn->output_plugin_private != NULL);
        pfree(txndata);
        txn->output_plugin_private = NULL;
    }

    if (data->skip_empty_xacts && !xact_wrote_changes)
        return;

    OutputPluginPrepareWrite(ctx, true);
    if (data->include_xids)
        appendStringInfo(ctx->out, "aborting streamed (sub)transaction TXN %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "aborting streamed (sub)transaction");
    OutputPluginWrite(ctx, true);
}

static void
pg_decode_stream_commit(LogicalDecodingContext *ctx,
                        ReorderBufferTXN *txn,
                        XLogRecPtr commit_lsn)
{
    TestDecodingData *data = ctx->output_plugin_private;
    TestDecodingTxnData *txndata = txn->output_plugin_private;
    bool        xact_wrote_changes = txndata->xact_wrote_changes;

    pfree(txndata);
    txn->output_plugin_private = NULL;

    if (data->skip_empty_xacts && !xact_wrote_changes)
        return;

    OutputPluginPrepareWrite(ctx, true);

    if (data->include_xids)
        appendStringInfo(ctx->out, "committing streamed transaction TXN %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "committing streamed transaction");

    if (data->include_timestamp)
        appendStringInfo(ctx->out, " (at %s)",
                         timestamptz_to_str(txn->commit_time));

    OutputPluginWrite(ctx, true);
}

/*
 * In streaming mode, we don't display the changes as the transaction can abort
 * at a later point in time.  We don't want users to see the changes until the
 * transaction is committed.
 */
static void
pg_decode_stream_change(LogicalDecodingContext *ctx,
                        ReorderBufferTXN *txn,
                        Relation relation,
                        ReorderBufferChange *change)
{
    TestDecodingData *data = ctx->output_plugin_private;
    TestDecodingTxnData *txndata = txn->output_plugin_private;

    /* output stream start if we haven't yet */
    if (data->skip_empty_xacts && !txndata->stream_wrote_changes)
    {
        pg_output_stream_start(ctx, data, txn, false);
    }
    txndata->xact_wrote_changes = txndata->stream_wrote_changes = true;

    OutputPluginPrepareWrite(ctx, true);
    if (data->include_xids)
        appendStringInfo(ctx->out, "streaming change for TXN %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "streaming change for transaction");
    OutputPluginWrite(ctx, true);
}

/*
 * In streaming mode, we don't display the contents for transactional messages
 * as the transaction can abort at a later point in time.  We don't want users to
 * see the message contents until the transaction is committed.
 */
static void
pg_decode_stream_message(LogicalDecodingContext *ctx,
                         ReorderBufferTXN *txn, XLogRecPtr lsn, bool transactional,
                         const char *prefix, Size sz, const char *message)
{
    OutputPluginPrepareWrite(ctx, true);

    if (transactional)
    {
        appendStringInfo(ctx->out, "streaming message: transactional: %d prefix: %s, sz: %zu",
                         transactional, prefix, sz);
    }
    else
    {
        appendStringInfo(ctx->out, "streaming message: transactional: %d prefix: %s, sz: %zu content:",
                         transactional, prefix, sz);
        appendBinaryStringInfo(ctx->out, message, sz);
    }

    OutputPluginWrite(ctx, true);
}

/*
 * In streaming mode, we don't display the detailed information of Truncate.
 * See pg_decode_stream_change.
 */
static void
pg_decode_stream_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
                          int nrelations, Relation relations[],
                          ReorderBufferChange *change)
{
    TestDecodingData *data = ctx->output_plugin_private;
    TestDecodingTxnData *txndata = txn->output_plugin_private;

    if (data->skip_empty_xacts && !txndata->stream_wrote_changes)
    {
        pg_output_stream_start(ctx, data, txn, false);
    }
    txndata->xact_wrote_changes = txndata->stream_wrote_changes = true;

    OutputPluginPrepareWrite(ctx, true);
    if (data->include_xids)
        appendStringInfo(ctx->out, "streaming truncate for TXN %u", txn->xid);
    else
        appendStringInfoString(ctx->out, "streaming truncate for transaction");
    OutputPluginWrite(ctx, true);
}