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plpy_main.c
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1 /*
2  * PL/Python main entry points
3  *
4  * src/pl/plpython/plpy_main.c
5  */
6 
7 #include "postgres.h"
8 
9 #include "access/htup_details.h"
10 #include "catalog/pg_proc.h"
11 #include "catalog/pg_type.h"
12 #include "commands/trigger.h"
13 #include "executor/spi.h"
14 #include "miscadmin.h"
15 #include "plpy_elog.h"
16 #include "plpy_exec.h"
17 #include "plpy_main.h"
18 #include "plpy_plpymodule.h"
19 #include "plpy_procedure.h"
20 #include "plpy_subxactobject.h"
21 #include "plpython.h"
22 #include "utils/guc.h"
23 #include "utils/memutils.h"
24 #include "utils/rel.h"
25 #include "utils/syscache.h"
26 
27 /*
28  * exported functions
29  */
30 
32 
36 
37 
38 static bool PLy_procedure_is_trigger(Form_pg_proc procStruct);
39 static void plpython_error_callback(void *arg);
40 static void plpython_inline_error_callback(void *arg);
41 static void PLy_init_interp(void);
42 
43 static PLyExecutionContext *PLy_push_execution_context(bool atomic_context);
44 static void PLy_pop_execution_context(void);
45 
46 /* static state for Python library conflict detection */
47 static int *plpython_version_bitmask_ptr = NULL;
48 static int plpython_version_bitmask = 0;
49 
50 /* initialize global variables */
51 PyObject *PLy_interp_globals = NULL;
52 
53 /* this doesn't need to be global; use PLy_current_execution_context() */
55 
56 
57 void
58 _PG_init(void)
59 {
60  int **bitmask_ptr;
61 
62  /*
63  * Set up a shared bitmask variable telling which Python version(s) are
64  * loaded into this process's address space. If there's more than one, we
65  * cannot call into libpython for fear of causing crashes. But postpone
66  * the actual failure for later, so that operations like pg_restore can
67  * load more than one plpython library so long as they don't try to do
68  * anything much with the language.
69  *
70  * While we only support Python 3 these days, somebody might create an
71  * out-of-tree version adding back support for Python 2. Conflicts with
72  * such an extension should be detected.
73  */
74  bitmask_ptr = (int **) find_rendezvous_variable("plpython_version_bitmask");
75  if (!(*bitmask_ptr)) /* am I the first? */
76  *bitmask_ptr = &plpython_version_bitmask;
77  /* Retain pointer to the agreed-on shared variable ... */
78  plpython_version_bitmask_ptr = *bitmask_ptr;
79  /* ... and announce my presence */
80  *plpython_version_bitmask_ptr |= (1 << PY_MAJOR_VERSION);
81 
82  /*
83  * This should be safe even in the presence of conflicting plpythons, and
84  * it's necessary to do it before possibly throwing a conflict error, or
85  * the error message won't get localized.
86  */
88 }
89 
90 /*
91  * Perform one-time setup of PL/Python, after checking for a conflict
92  * with other versions of Python.
93  */
94 static void
96 {
97  static bool inited = false;
98 
99  /*
100  * Check for multiple Python libraries before actively doing anything with
101  * libpython. This must be repeated on each entry to PL/Python, in case a
102  * conflicting library got loaded since we last looked.
103  *
104  * It is attractive to weaken this error from FATAL to ERROR, but there
105  * would be corner cases, so it seems best to be conservative.
106  */
107  if (*plpython_version_bitmask_ptr != (1 << PY_MAJOR_VERSION))
108  ereport(FATAL,
109  (errmsg("multiple Python libraries are present in session"),
110  errdetail("Only one Python major version can be used in one session.")));
111 
112  /* The rest should only be done once per session */
113  if (inited)
114  return;
115 
116  PyImport_AppendInittab("plpy", PyInit_plpy);
117  Py_Initialize();
118  PyImport_ImportModule("plpy");
119  PLy_init_interp();
120  PLy_init_plpy();
121  if (PyErr_Occurred())
122  PLy_elog(FATAL, "untrapped error in initialization");
123 
125 
127 
128  PLy_execution_contexts = NULL;
129 
130  inited = true;
131 }
132 
133 /*
134  * This should be called only once, from PLy_initialize. Initialize the Python
135  * interpreter and global data.
136  */
137 static void
139 {
140  static PyObject *PLy_interp_safe_globals = NULL;
141  PyObject *mainmod;
142 
143  mainmod = PyImport_AddModule("__main__");
144  if (mainmod == NULL || PyErr_Occurred())
145  PLy_elog(ERROR, "could not import \"__main__\" module");
146  Py_INCREF(mainmod);
147  PLy_interp_globals = PyModule_GetDict(mainmod);
148  PLy_interp_safe_globals = PyDict_New();
149  if (PLy_interp_safe_globals == NULL)
150  PLy_elog(ERROR, NULL);
151  PyDict_SetItemString(PLy_interp_globals, "GD", PLy_interp_safe_globals);
152  Py_DECREF(mainmod);
153  if (PLy_interp_globals == NULL || PyErr_Occurred())
154  PLy_elog(ERROR, "could not initialize globals");
155 }
156 
157 Datum
159 {
160  Oid funcoid = PG_GETARG_OID(0);
161  HeapTuple tuple;
162  Form_pg_proc procStruct;
163  bool is_trigger;
164 
165  if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
166  PG_RETURN_VOID();
167 
169  PG_RETURN_VOID();
170 
171  /* Do this only after making sure we need to do something */
172  PLy_initialize();
173 
174  /* Get the new function's pg_proc entry */
175  tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcoid));
176  if (!HeapTupleIsValid(tuple))
177  elog(ERROR, "cache lookup failed for function %u", funcoid);
178  procStruct = (Form_pg_proc) GETSTRUCT(tuple);
179 
180  is_trigger = PLy_procedure_is_trigger(procStruct);
181 
182  ReleaseSysCache(tuple);
183 
184  /* We can't validate triggers against any particular table ... */
185  PLy_procedure_get(funcoid, InvalidOid, is_trigger);
186 
187  PG_RETURN_VOID();
188 }
189 
190 Datum
192 {
193  bool nonatomic;
194  Datum retval;
195  PLyExecutionContext *exec_ctx;
196  ErrorContextCallback plerrcontext;
197 
198  PLy_initialize();
199 
200  nonatomic = fcinfo->context &&
201  IsA(fcinfo->context, CallContext) &&
202  !castNode(CallContext, fcinfo->context)->atomic;
203 
204  /* Note: SPI_finish() happens in plpy_exec.c, which is dubious design */
205  SPI_connect_ext(nonatomic ? SPI_OPT_NONATOMIC : 0);
206 
207  /*
208  * Push execution context onto stack. It is important that this get
209  * popped again, so avoid putting anything that could throw error between
210  * here and the PG_TRY.
211  */
212  exec_ctx = PLy_push_execution_context(!nonatomic);
213 
214  PG_TRY();
215  {
216  Oid funcoid = fcinfo->flinfo->fn_oid;
217  PLyProcedure *proc;
218 
219  /*
220  * Setup error traceback support for ereport(). Note that the PG_TRY
221  * structure pops this for us again at exit, so we needn't do that
222  * explicitly, nor do we risk the callback getting called after we've
223  * destroyed the exec_ctx.
224  */
225  plerrcontext.callback = plpython_error_callback;
226  plerrcontext.arg = exec_ctx;
227  plerrcontext.previous = error_context_stack;
228  error_context_stack = &plerrcontext;
229 
230  if (CALLED_AS_TRIGGER(fcinfo))
231  {
232  Relation tgrel = ((TriggerData *) fcinfo->context)->tg_relation;
233  HeapTuple trv;
234 
235  proc = PLy_procedure_get(funcoid, RelationGetRelid(tgrel), true);
236  exec_ctx->curr_proc = proc;
237  trv = PLy_exec_trigger(fcinfo, proc);
238  retval = PointerGetDatum(trv);
239  }
240  else
241  {
242  proc = PLy_procedure_get(funcoid, InvalidOid, false);
243  exec_ctx->curr_proc = proc;
244  retval = PLy_exec_function(fcinfo, proc);
245  }
246  }
247  PG_CATCH();
248  {
250  PyErr_Clear();
251  PG_RE_THROW();
252  }
253  PG_END_TRY();
254 
255  /* Destroy the execution context */
257 
258  return retval;
259 }
260 
261 Datum
263 {
264  LOCAL_FCINFO(fake_fcinfo, 0);
266  FmgrInfo flinfo;
267  PLyProcedure proc;
268  PLyExecutionContext *exec_ctx;
269  ErrorContextCallback plerrcontext;
270 
271  PLy_initialize();
272 
273  /* Note: SPI_finish() happens in plpy_exec.c, which is dubious design */
274  SPI_connect_ext(codeblock->atomic ? 0 : SPI_OPT_NONATOMIC);
275 
276  MemSet(fcinfo, 0, SizeForFunctionCallInfo(0));
277  MemSet(&flinfo, 0, sizeof(flinfo));
278  fake_fcinfo->flinfo = &flinfo;
279  flinfo.fn_oid = InvalidOid;
280  flinfo.fn_mcxt = CurrentMemoryContext;
281 
282  MemSet(&proc, 0, sizeof(PLyProcedure));
284  "__plpython_inline_block",
286  proc.pyname = MemoryContextStrdup(proc.mcxt, "__plpython_inline_block");
287  proc.langid = codeblock->langOid;
288 
289  /*
290  * This is currently sufficient to get PLy_exec_function to work, but
291  * someday we might need to be honest and use PLy_output_setup_func.
292  */
293  proc.result.typoid = VOIDOID;
294 
295  /*
296  * Push execution context onto stack. It is important that this get
297  * popped again, so avoid putting anything that could throw error between
298  * here and the PG_TRY.
299  */
300  exec_ctx = PLy_push_execution_context(codeblock->atomic);
301 
302  PG_TRY();
303  {
304  /*
305  * Setup error traceback support for ereport().
306  * plpython_inline_error_callback doesn't currently need exec_ctx, but
307  * for consistency with plpython3_call_handler we do it the same way.
308  */
310  plerrcontext.arg = exec_ctx;
311  plerrcontext.previous = error_context_stack;
312  error_context_stack = &plerrcontext;
313 
314  PLy_procedure_compile(&proc, codeblock->source_text);
315  exec_ctx->curr_proc = &proc;
316  PLy_exec_function(fake_fcinfo, &proc);
317  }
318  PG_CATCH();
319  {
321  PLy_procedure_delete(&proc);
322  PyErr_Clear();
323  PG_RE_THROW();
324  }
325  PG_END_TRY();
326 
327  /* Destroy the execution context */
329 
330  /* Now clean up the transient procedure we made */
331  PLy_procedure_delete(&proc);
332 
333  PG_RETURN_VOID();
334 }
335 
336 static bool
338 {
339  return (procStruct->prorettype == TRIGGEROID);
340 }
341 
342 static void
344 {
346 
347  if (exec_ctx->curr_proc)
348  {
349  if (exec_ctx->curr_proc->is_procedure)
350  errcontext("PL/Python procedure \"%s\"",
351  PLy_procedure_name(exec_ctx->curr_proc));
352  else
353  errcontext("PL/Python function \"%s\"",
354  PLy_procedure_name(exec_ctx->curr_proc));
355  }
356 }
357 
358 static void
360 {
361  errcontext("PL/Python anonymous code block");
362 }
363 
366 {
367  if (PLy_execution_contexts == NULL)
368  elog(ERROR, "no Python function is currently executing");
369 
370  return PLy_execution_contexts;
371 }
372 
375 {
376  /*
377  * A scratch context might never be needed in a given plpython procedure,
378  * so allocate it on first request.
379  */
380  if (context->scratch_ctx == NULL)
381  context->scratch_ctx =
383  "PL/Python scratch context",
385  return context->scratch_ctx;
386 }
387 
388 static PLyExecutionContext *
389 PLy_push_execution_context(bool atomic_context)
390 {
392 
393  /* Pick a memory context similar to what SPI uses. */
396  sizeof(PLyExecutionContext));
397  context->curr_proc = NULL;
398  context->scratch_ctx = NULL;
401  return context;
402 }
403 
404 static void
406 {
408 
409  if (context == NULL)
410  elog(ERROR, "no Python function is currently executing");
411 
413 
414  if (context->scratch_ctx)
415  MemoryContextDelete(context->scratch_ctx);
416  pfree(context);
417 }
#define MemSet(start, val, len)
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Definition: plpy_exec.c:55
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Definition: plpy_main.c:48
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