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pg_json_decoding.c
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pg_json_decoding.c
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#include "postgres.h"
#include "catalog/namespace.h"
#include "replication/logical.h"
#include "common/base64.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/relcache.h"
#include "utils/syscache.h"
#include "utils/json.h"
#include "utils/builtins.h"
PG_MODULE_MAGIC;
extern void _PG_init(void);
extern void _PG_output_plugin_init(OutputPluginCallbacks *cb);
typedef struct _JsonDecodingData {
MemoryContext context;
char *pubname;
Oid pubid;
bool puballtables;
} JsonDecodingData;
static void pg_decode_startup(
LogicalDecodingContext *ctx,
OutputPluginOptions *opt,
bool is_init
) {
JsonDecodingData *data;
ListCell *option;
data = palloc0(sizeof(JsonDecodingData));
data->pubname = NULL;
data->pubid = InvalidOid;
data->puballtables = false;
data->context = AllocSetContextCreate(
ctx->context,
"pg_json_decoding context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE
);
ctx->output_plugin_private = data;
opt->output_type = OUTPUT_PLUGIN_TEXTUAL_OUTPUT;
if (is_init) {
return;
}
foreach(option, ctx->output_plugin_options) {
DefElem *elem = lfirst(option);
Assert(elem->arg == NULL || IsA(elem->arg, String));
if (strcmp(elem->defname, "publication") == 0) {
data->pubname = strVal(elem->arg);
}
}
if (data->pubname == NULL) {
ereport(ERROR, (
errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("publication parameter missing")
));
}
}
static void pg_decode_shutdown(LogicalDecodingContext *ctx) {
JsonDecodingData *data = ctx->output_plugin_private;
MemoryContextDelete(data->context);
}
static void pg_decode_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn) {
OutputPluginPrepareWrite(ctx, true);
appendStringInfo(
ctx->out,
"{\"kind\":\"begin\",\"committed\":\"%ld\"}",
txn->commit_time + (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * USECS_PER_DAY
);
OutputPluginWrite(ctx, true);
}
static void pg_decode_commit_txn(
LogicalDecodingContext *ctx,
ReorderBufferTXN *txn,
XLogRecPtr commit_lsn
) {
OutputPluginPrepareWrite(ctx, true);
appendStringInfoString(ctx->out, "{\"kind\":\"commit\"}");
OutputPluginWrite(ctx, true);
}
static void tuple_to_json(StringInfo out, TupleDesc tupdesc, HeapTuple tuple) {
Datum tupdat = heap_copy_tuple_as_datum(tuple, tupdesc);
Datum tupjson = DirectFunctionCall1(row_to_json, tupdat);
char *tupjsonstr = TextDatumGetCString(tupjson);
appendStringInfoString(out, tupjsonstr);
}
static void pg_decode_change(
LogicalDecodingContext *ctx,
ReorderBufferTXN *txn,
Relation relation,
ReorderBufferChange *change
) {
JsonDecodingData *data;
Form_pg_class class_form;
TupleDesc tupdesc;
MemoryContext old;
char *table_name;
data = ctx->output_plugin_private;
if (data->pubid == InvalidOid) {
data->pubid = get_publication_oid(data->pubname, false);
data->puballtables = GetPublication(data->pubid)->alltables;
}
if (!data->puballtables && !SearchSysCacheExists2(
PUBLICATIONRELMAP,
ObjectIdGetDatum(RelationGetRelid(relation)),
ObjectIdGetDatum(data->pubid)
)) {
return;
}
class_form = RelationGetForm(relation);
tupdesc = RelationGetDescr(relation);
table_name = NameStr(class_form->relname);
old = MemoryContextSwitchTo(data->context);
OutputPluginPrepareWrite(ctx, true);
appendStringInfoString(ctx->out, "{\"kind\":");
switch (change->action) {
case REORDER_BUFFER_CHANGE_INSERT:
appendStringInfoString(ctx->out, "\"insert\"");
break;
case REORDER_BUFFER_CHANGE_UPDATE:
appendStringInfoString(ctx->out, "\"update\"");
break;
case REORDER_BUFFER_CHANGE_DELETE:
appendStringInfoString(ctx->out, "\"delete\"");
break;
default:
appendStringInfoString(ctx->out, "\"unknown\"");
break;
}
appendStringInfoString(ctx->out, ",\"schema\":");
escape_json(ctx->out, get_namespace_name(
get_rel_namespace(RelationGetRelid(relation))
));
appendStringInfoString(ctx->out, ",\"table\":");
escape_json(ctx->out, table_name);
if (change->data.tp.oldtuple != NULL) {
appendStringInfoString(ctx->out, ",\"oldtuple\":");
tuple_to_json(ctx->out, tupdesc, &change->data.tp.oldtuple->tuple);
}
if (change->data.tp.newtuple != NULL) {
appendStringInfoString(ctx->out, ",\"newtuple\":");
tuple_to_json(ctx->out, tupdesc, &change->data.tp.newtuple->tuple);
}
appendStringInfoChar(ctx->out, '}');
MemoryContextSwitchTo(old);
MemoryContextReset(data->context);
OutputPluginWrite(ctx, true);
}
static void pg_decode_truncate(
LogicalDecodingContext *ctx,
ReorderBufferTXN *txn,
int nrelations,
Relation relations[],
ReorderBufferChange *change
) {
OutputPluginPrepareWrite(ctx, true);
appendStringInfoString(ctx->out, "{\"kind\":\"truncate\"}");
OutputPluginWrite(ctx, true);
}
static void pg_decode_message(
LogicalDecodingContext *ctx,
ReorderBufferTXN *txn,
XLogRecPtr lsn,
bool transactional,
const char *prefix,
Size sz,
const char *message
) {
JsonDecodingData *data;
MemoryContext old;
char *message_b64;
data = ctx->output_plugin_private;
old = MemoryContextSwitchTo(data->context);
OutputPluginPrepareWrite(ctx, true);
if (transactional) {
appendStringInfoString(ctx->out, "{\"kind\":\"xmessage\"");
} else {
appendStringInfoString(ctx->out, "{\"kind\":\"message\"");
}
appendStringInfoString(ctx->out, ",\"prefix\":");
escape_json(ctx->out, prefix);
message_b64 = palloc0(pg_b64_enc_len(sz) + 1);
pg_b64_encode(message, sz, message_b64);
appendStringInfo(ctx->out, ",\"content\":\"%s\"}", message_b64);
pfree(message_b64);
MemoryContextSwitchTo(old);
MemoryContextReset(data->context);
OutputPluginWrite(ctx, true);
}
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->commit_cb = pg_decode_commit_txn;
cb->shutdown_cb = pg_decode_shutdown;
cb->message_cb = pg_decode_message;
cb->truncate_cb = pg_decode_truncate;
}
void _PG_init(void) {
}