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logicalfuncs.c
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1 /*-------------------------------------------------------------------------
2  *
3  * logicalfuncs.c
4  *
5  * Support functions for using logical decoding and management of
6  * logical replication slots via SQL.
7  *
8  *
9  * Copyright (c) 2012-2024, PostgreSQL Global Development Group
10  *
11  * IDENTIFICATION
12  * src/backend/replication/logical/logicalfuncs.c
13  *-------------------------------------------------------------------------
14  */
15 
16 #include "postgres.h"
17 
18 #include <unistd.h>
19 
20 #include "access/xact.h"
21 #include "access/xlog_internal.h"
22 #include "access/xlogrecovery.h"
23 #include "access/xlogutils.h"
24 #include "catalog/pg_type.h"
25 #include "fmgr.h"
26 #include "funcapi.h"
27 #include "mb/pg_wchar.h"
28 #include "miscadmin.h"
29 #include "nodes/makefuncs.h"
30 #include "replication/decode.h"
31 #include "replication/logical.h"
32 #include "replication/message.h"
33 #include "storage/fd.h"
34 #include "utils/array.h"
35 #include "utils/builtins.h"
36 #include "utils/inval.h"
37 #include "utils/lsyscache.h"
38 #include "utils/memutils.h"
39 #include "utils/pg_lsn.h"
40 #include "utils/regproc.h"
41 #include "utils/resowner.h"
42 
43 /* Private data for writing out data */
44 typedef struct DecodingOutputState
45 {
51 
52 /*
53  * Prepare for an output plugin write.
54  */
55 static void
57  bool last_write)
58 {
59  resetStringInfo(ctx->out);
60 }
61 
62 /*
63  * Perform output plugin write into tuplestore.
64  */
65 static void
67  bool last_write)
68 {
69  Datum values[3];
70  bool nulls[3];
72 
73  /* SQL Datums can only be of a limited length... */
74  if (ctx->out->len > MaxAllocSize - VARHDRSZ)
75  elog(ERROR, "too much output for sql interface");
76 
78 
79  memset(nulls, 0, sizeof(nulls));
80  values[0] = LSNGetDatum(lsn);
81  values[1] = TransactionIdGetDatum(xid);
82 
83  /*
84  * Assert ctx->out is in database encoding when we're writing textual
85  * output.
86  */
87  if (!p->binary_output)
89  ctx->out->data, ctx->out->len,
90  false));
91 
92  /* ick, but cstring_to_text_with_len works for bytea perfectly fine */
94 
96  p->returned_rows++;
97 }
98 
99 /*
100  * Helper function for the various SQL callable logical decoding functions.
101  */
102 static Datum
103 pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool binary)
104 {
105  Name name;
106  XLogRecPtr upto_lsn;
107  int32 upto_nchanges;
108  ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
109  MemoryContext per_query_ctx;
110  MemoryContext oldcontext;
111  XLogRecPtr end_of_wal;
113  ResourceOwner old_resowner = CurrentResourceOwner;
114  ArrayType *arr;
115  Size ndim;
116  List *options = NIL;
118 
120 
122 
123  if (PG_ARGISNULL(0))
124  ereport(ERROR,
125  (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
126  errmsg("slot name must not be null")));
127  name = PG_GETARG_NAME(0);
128 
129  if (PG_ARGISNULL(1))
130  upto_lsn = InvalidXLogRecPtr;
131  else
132  upto_lsn = PG_GETARG_LSN(1);
133 
134  if (PG_ARGISNULL(2))
135  upto_nchanges = InvalidXLogRecPtr;
136  else
137  upto_nchanges = PG_GETARG_INT32(2);
138 
139  if (PG_ARGISNULL(3))
140  ereport(ERROR,
141  (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
142  errmsg("options array must not be null")));
143  arr = PG_GETARG_ARRAYTYPE_P(3);
144 
145  /* state to write output to */
146  p = palloc0(sizeof(DecodingOutputState));
147 
148  p->binary_output = binary;
149 
150  per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
151  oldcontext = MemoryContextSwitchTo(per_query_ctx);
152 
153  /* Deconstruct options array */
154  ndim = ARR_NDIM(arr);
155  if (ndim > 1)
156  {
157  ereport(ERROR,
158  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
159  errmsg("array must be one-dimensional")));
160  }
161  else if (array_contains_nulls(arr))
162  {
163  ereport(ERROR,
164  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
165  errmsg("array must not contain nulls")));
166  }
167  else if (ndim == 1)
168  {
169  int nelems;
170  Datum *datum_opts;
171  int i;
172 
173  Assert(ARR_ELEMTYPE(arr) == TEXTOID);
174 
175  deconstruct_array_builtin(arr, TEXTOID, &datum_opts, NULL, &nelems);
176 
177  if (nelems % 2 != 0)
178  ereport(ERROR,
179  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
180  errmsg("array must have even number of elements")));
181 
182  for (i = 0; i < nelems; i += 2)
183  {
184  char *optname = TextDatumGetCString(datum_opts[i]);
185  char *opt = TextDatumGetCString(datum_opts[i + 1]);
186 
187  options = lappend(options, makeDefElem(optname, (Node *) makeString(opt), -1));
188  }
189  }
190 
191  InitMaterializedSRF(fcinfo, 0);
192  p->tupstore = rsinfo->setResult;
193  p->tupdesc = rsinfo->setDesc;
194 
195  /*
196  * Compute the current end-of-wal.
197  */
198  if (!RecoveryInProgress())
199  end_of_wal = GetFlushRecPtr(NULL);
200  else
201  end_of_wal = GetXLogReplayRecPtr(NULL);
202 
204 
205  PG_TRY();
206  {
207  /* restart at slot's confirmed_flush */
209  options,
210  false,
211  XL_ROUTINE(.page_read = read_local_xlog_page,
212  .segment_open = wal_segment_open,
213  .segment_close = wal_segment_close),
215  LogicalOutputWrite, NULL);
216 
217  MemoryContextSwitchTo(oldcontext);
218 
219  /*
220  * Check whether the output plugin writes textual output if that's
221  * what we need.
222  */
223  if (!binary &&
224  ctx->options.output_type !=OUTPUT_PLUGIN_TEXTUAL_OUTPUT)
225  ereport(ERROR,
226  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
227  errmsg("logical decoding output plugin \"%s\" produces binary output, but function \"%s\" expects textual data",
229  format_procedure(fcinfo->flinfo->fn_oid))));
230 
231  ctx->output_writer_private = p;
232 
233  /*
234  * Decoding of WAL must start at restart_lsn so that the entirety of
235  * xacts that committed after the slot's confirmed_flush can be
236  * accumulated into reorder buffers.
237  */
239 
240  /* invalidate non-timetravel entries */
242 
243  /* Decode until we run out of records */
244  while (ctx->reader->EndRecPtr < end_of_wal)
245  {
246  XLogRecord *record;
247  char *errm = NULL;
248 
249  record = XLogReadRecord(ctx->reader, &errm);
250  if (errm)
251  elog(ERROR, "could not find record for logical decoding: %s", errm);
252 
253  /*
254  * The {begin_txn,change,commit_txn}_wrapper callbacks above will
255  * store the description into our tuplestore.
256  */
257  if (record != NULL)
258  LogicalDecodingProcessRecord(ctx, ctx->reader);
259 
260  /* check limits */
261  if (upto_lsn != InvalidXLogRecPtr &&
262  upto_lsn <= ctx->reader->EndRecPtr)
263  break;
264  if (upto_nchanges != 0 &&
265  upto_nchanges <= p->returned_rows)
266  break;
268  }
269 
270  /*
271  * Logical decoding could have clobbered CurrentResourceOwner during
272  * transaction management, so restore the executor's value. (This is
273  * a kluge, but it's not worth cleaning up right now.)
274  */
275  CurrentResourceOwner = old_resowner;
276 
277  /*
278  * Next time, start where we left off. (Hunting things, the family
279  * business..)
280  */
281  if (ctx->reader->EndRecPtr != InvalidXLogRecPtr && confirm)
282  {
283  LogicalConfirmReceivedLocation(ctx->reader->EndRecPtr);
284 
285  /*
286  * If only the confirmed_flush_lsn has changed the slot won't get
287  * marked as dirty by the above. Callers on the walsender
288  * interface are expected to keep track of their own progress and
289  * don't need it written out. But SQL-interface users cannot
290  * specify their own start positions and it's harder for them to
291  * keep track of their progress, so we should make more of an
292  * effort to save it for them.
293  *
294  * Dirty the slot so it's written out at the next checkpoint.
295  * We'll still lose its position on crash, as documented, but it's
296  * better than always losing the position even on clean restart.
297  */
299  }
300 
301  /* free context, call shutdown callback */
302  FreeDecodingContext(ctx);
303 
306  }
307  PG_CATCH();
308  {
309  /* clear all timetravel entries */
311 
312  PG_RE_THROW();
313  }
314  PG_END_TRY();
315 
316  return (Datum) 0;
317 }
318 
319 /*
320  * SQL function returning the changestream as text, consuming the data.
321  */
322 Datum
324 {
325  return pg_logical_slot_get_changes_guts(fcinfo, true, false);
326 }
327 
328 /*
329  * SQL function returning the changestream as text, only peeking ahead.
330  */
331 Datum
333 {
334  return pg_logical_slot_get_changes_guts(fcinfo, false, false);
335 }
336 
337 /*
338  * SQL function returning the changestream in binary, consuming the data.
339  */
340 Datum
342 {
343  return pg_logical_slot_get_changes_guts(fcinfo, true, true);
344 }
345 
346 /*
347  * SQL function returning the changestream in binary, only peeking ahead.
348  */
349 Datum
351 {
352  return pg_logical_slot_get_changes_guts(fcinfo, false, true);
353 }
354 
355 
356 /*
357  * SQL function for writing logical decoding message into WAL.
358  */
359 Datum
361 {
362  bool transactional = PG_GETARG_BOOL(0);
363  char *prefix = text_to_cstring(PG_GETARG_TEXT_PP(1));
365  bool flush = PG_GETARG_BOOL(3);
366  XLogRecPtr lsn;
367 
369  transactional, flush);
370  PG_RETURN_LSN(lsn);
371 }
372 
373 Datum
375 {
376  /* bytea and text are compatible */
377  return pg_logical_emit_message_bytea(fcinfo);
378 }
#define ARR_NDIM(a)
Definition: array.h:290
#define PG_GETARG_ARRAYTYPE_P(n)
Definition: array.h:263
#define ARR_ELEMTYPE(a)
Definition: array.h:292
bool array_contains_nulls(ArrayType *array)
Definition: arrayfuncs.c:3749
void deconstruct_array_builtin(ArrayType *array, Oid elmtype, Datum **elemsp, bool **nullsp, int *nelemsp)
Definition: arrayfuncs.c:3679
static Datum values[MAXATTR]
Definition: bootstrap.c:156
#define TextDatumGetCString(d)
Definition: builtins.h:98
#define NameStr(name)
Definition: c.h:735
signed int int32
Definition: c.h:483
#define VARHDRSZ
Definition: c.h:681
uint32 TransactionId
Definition: c.h:641
size_t Size
Definition: c.h:594
void LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *record)
Definition: decode.c:91
int errcode(int sqlerrcode)
Definition: elog.c:860
int errmsg(const char *fmt,...)
Definition: elog.c:1075
#define PG_RE_THROW()
Definition: elog.h:411
#define PG_TRY(...)
Definition: elog.h:370
#define PG_END_TRY(...)
Definition: elog.h:395
#define ERROR
Definition: elog.h:39
#define PG_CATCH(...)
Definition: elog.h:380
#define ereport(elevel,...)
Definition: elog.h:149
#define PG_GETARG_BYTEA_PP(n)
Definition: fmgr.h:308
#define PG_GETARG_TEXT_PP(n)
Definition: fmgr.h:309
#define PG_ARGISNULL(n)
Definition: fmgr.h:209
#define PG_GETARG_NAME(n)
Definition: fmgr.h:278
#define PG_GETARG_INT32(n)
Definition: fmgr.h:269
#define PG_GETARG_BOOL(n)
Definition: fmgr.h:274
#define PG_FUNCTION_ARGS
Definition: fmgr.h:193
void InitMaterializedSRF(FunctionCallInfo fcinfo, bits32 flags)
Definition: funcapi.c:76
void InvalidateSystemCaches(void)
Definition: inval.c:793
int i
Definition: isn.c:73
Assert(fmt[strlen(fmt) - 1] !='\n')
List * lappend(List *list, void *datum)
Definition: list.c:339
void LogicalConfirmReceivedLocation(XLogRecPtr lsn)
Definition: logical.c:1829
void FreeDecodingContext(LogicalDecodingContext *ctx)
Definition: logical.c:688
void CheckLogicalDecodingRequirements(void)
Definition: logical.c:110
LogicalDecodingContext * CreateDecodingContext(XLogRecPtr start_lsn, List *output_plugin_options, bool fast_forward, XLogReaderRoutine *xl_routine, LogicalOutputPluginWriterPrepareWrite prepare_write, LogicalOutputPluginWriterWrite do_write, LogicalOutputPluginWriterUpdateProgress update_progress)
Definition: logical.c:496
static void LogicalOutputPrepareWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write)
Definition: logicalfuncs.c:56
Datum pg_logical_slot_get_changes(PG_FUNCTION_ARGS)
Definition: logicalfuncs.c:323
static void LogicalOutputWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write)
Definition: logicalfuncs.c:66
Datum pg_logical_emit_message_bytea(PG_FUNCTION_ARGS)
Definition: logicalfuncs.c:360
Datum pg_logical_slot_get_binary_changes(PG_FUNCTION_ARGS)
Definition: logicalfuncs.c:341
Datum pg_logical_emit_message_text(PG_FUNCTION_ARGS)
Definition: logicalfuncs.c:374
Datum pg_logical_slot_peek_binary_changes(PG_FUNCTION_ARGS)
Definition: logicalfuncs.c:350
Datum pg_logical_slot_peek_changes(PG_FUNCTION_ARGS)
Definition: logicalfuncs.c:332
struct DecodingOutputState DecodingOutputState
static Datum pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool binary)
Definition: logicalfuncs.c:103
DefElem * makeDefElem(char *name, Node *arg, int location)
Definition: makefuncs.c:549
int GetDatabaseEncoding(void)
Definition: mbutils.c:1268
bool pg_verify_mbstr(int encoding, const char *mbstr, int len, bool noError)
Definition: mbutils.c:1573
void * palloc0(Size size)
Definition: mcxt.c:1232
#define MaxAllocSize
Definition: memutils.h:40
XLogRecPtr LogLogicalMessage(const char *prefix, const char *message, size_t size, bool transactional, bool flush)
Definition: message.c:46
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:122
@ OUTPUT_PLUGIN_TEXTUAL_OUTPUT
Definition: output_plugin.h:20
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
Definition: palloc.h:124
const void * data
#define NIL
Definition: pg_list.h:68
#define PG_GETARG_LSN(n)
Definition: pg_lsn.h:33
static Datum LSNGetDatum(XLogRecPtr X)
Definition: pg_lsn.h:28
#define PG_RETURN_LSN(x)
Definition: pg_lsn.h:34
static Datum PointerGetDatum(const void *X)
Definition: postgres.h:322
static Datum TransactionIdGetDatum(TransactionId X)
Definition: postgres.h:272
uintptr_t Datum
Definition: postgres.h:64
char * format_procedure(Oid procedure_oid)
Definition: regproc.c:299
ResourceOwner CurrentResourceOwner
Definition: resowner.c:165
void ReplicationSlotMarkDirty(void)
Definition: slot.c:946
void ReplicationSlotAcquire(const char *name, bool nowait)
Definition: slot.c:502
ReplicationSlot * MyReplicationSlot
Definition: slot.c:116
void CheckSlotPermissions(void)
Definition: slot.c:1320
void ReplicationSlotRelease(void)
Definition: slot.c:606
void resetStringInfo(StringInfo str)
Definition: stringinfo.c:78
Tuplestorestate * tupstore
Definition: logicalfuncs.c:46
MemoryContext ecxt_per_query_memory
Definition: execnodes.h:262
Oid fn_oid
Definition: fmgr.h:59
fmNodePtr resultinfo
Definition: fmgr.h:89
FmgrInfo * flinfo
Definition: fmgr.h:87
Definition: pg_list.h:54
void * output_writer_private
Definition: logical.h:81
StringInfo out
Definition: logical.h:71
Definition: nodes.h:129
XLogRecPtr restart_lsn
Definition: slot.h:93
ReplicationSlotPersistentData data
Definition: slot.h:178
ExprContext * econtext
Definition: execnodes.h:332
TupleDesc setDesc
Definition: execnodes.h:340
Tuplestorestate * setResult
Definition: execnodes.h:339
Definition: c.h:730
Definition: c.h:676
void tuplestore_putvalues(Tuplestorestate *state, TupleDesc tdesc, const Datum *values, const bool *isnull)
Definition: tuplestore.c:750
String * makeString(char *str)
Definition: value.c:63
#define VARDATA_ANY(PTR)
Definition: varatt.h:324
#define VARSIZE_ANY_EXHDR(PTR)
Definition: varatt.h:317
char * text_to_cstring(const text *t)
Definition: varlena.c:217
text * cstring_to_text_with_len(const char *s, int len)
Definition: varlena.c:196
const char * name
bool RecoveryInProgress(void)
Definition: xlog.c:6211
XLogRecPtr GetFlushRecPtr(TimeLineID *insertTLI)
Definition: xlog.c:6376
uint64 XLogRecPtr
Definition: xlogdefs.h:21
#define InvalidXLogRecPtr
Definition: xlogdefs.h:28
XLogRecord * XLogReadRecord(XLogReaderState *state, char **errormsg)
Definition: xlogreader.c:391
void XLogBeginRead(XLogReaderState *state, XLogRecPtr RecPtr)
Definition: xlogreader.c:233
#define XL_ROUTINE(...)
Definition: xlogreader.h:117
XLogRecPtr GetXLogReplayRecPtr(TimeLineID *replayTLI)
void wal_segment_close(XLogReaderState *state)
Definition: xlogutils.c:845
void wal_segment_open(XLogReaderState *state, XLogSegNo nextSegNo, TimeLineID *tli_p)
Definition: xlogutils.c:820
int read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetRecPtr, char *cur_page)
Definition: xlogutils.c:864