TLA Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * toast_helper.c
4 : * Helper functions for table AMs implementing compressed or
5 : * out-of-line storage of varlena attributes.
6 : *
7 : * Copyright (c) 2000-2023, PostgreSQL Global Development Group
8 : *
9 : * IDENTIFICATION
10 : * src/backend/access/table/toast_helper.c
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 :
15 : #include "postgres.h"
16 :
17 : #include "access/detoast.h"
18 : #include "access/table.h"
19 : #include "access/toast_helper.h"
20 : #include "access/toast_internals.h"
21 : #include "catalog/pg_type_d.h"
22 : #include "varatt.h"
23 :
24 :
25 : /*
26 : * Prepare to TOAST a tuple.
27 : *
28 : * tupleDesc, toast_values, and toast_isnull are required parameters; they
29 : * provide the necessary details about the tuple to be toasted.
30 : *
31 : * toast_oldvalues and toast_oldisnull should be NULL for a newly-inserted
32 : * tuple; for an update, they should describe the existing tuple.
33 : *
34 : * All of these arrays should have a length equal to tupleDesc->natts.
35 : *
36 : * On return, toast_flags and toast_attr will have been initialized.
37 : * toast_flags is just a single uint8, but toast_attr is a caller-provided
38 : * array with a length equal to tupleDesc->natts. The caller need not
39 : * perform any initialization of the array before calling this function.
40 : */
41 : void
42 GIC 63963 : toast_tuple_init(ToastTupleContext *ttc)
43 ECB : {
44 GIC 63963 : TupleDesc tupleDesc = ttc->ttc_rel->rd_att;
45 CBC 63963 : int numAttrs = tupleDesc->natts;
46 ECB : int i;
47 :
48 GIC 63963 : ttc->ttc_flags = 0;
49 ECB :
50 GIC 796506 : for (i = 0; i < numAttrs; i++)
51 ECB : {
52 GIC 732543 : Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
53 ECB : struct varlena *old_value;
54 : struct varlena *new_value;
55 :
56 GIC 732543 : ttc->ttc_attr[i].tai_colflags = 0;
57 CBC 732543 : ttc->ttc_attr[i].tai_oldexternal = NULL;
58 732543 : ttc->ttc_attr[i].tai_compression = att->attcompression;
59 ECB :
60 GIC 732543 : if (ttc->ttc_oldvalues != NULL)
61 ECB : {
62 : /*
63 : * For UPDATE get the old and new values of this attribute
64 : */
65 : old_value =
66 GIC 87351 : (struct varlena *) DatumGetPointer(ttc->ttc_oldvalues[i]);
67 ECB : new_value =
68 GIC 87351 : (struct varlena *) DatumGetPointer(ttc->ttc_values[i]);
69 ECB :
70 : /*
71 : * If the old value is stored on disk, check if it has changed so
72 : * we have to delete it later.
73 : */
74 GIC 87351 : if (att->attlen == -1 && !ttc->ttc_oldisnull[i] &&
75 CBC 8838 : VARATT_IS_EXTERNAL_ONDISK(old_value))
76 ECB : {
77 GIC 261 : if (ttc->ttc_isnull[i] ||
78 CBC 252 : !VARATT_IS_EXTERNAL_ONDISK(new_value) ||
79 48 : memcmp((char *) old_value, (char *) new_value,
80 48 : VARSIZE_EXTERNAL(old_value)) != 0)
81 ECB : {
82 : /*
83 : * The old external stored value isn't needed any more
84 : * after the update
85 : */
86 GIC 214 : ttc->ttc_attr[i].tai_colflags |= TOASTCOL_NEEDS_DELETE_OLD;
87 CBC 214 : ttc->ttc_flags |= TOAST_NEEDS_DELETE_OLD;
88 ECB : }
89 : else
90 : {
91 : /*
92 : * This attribute isn't changed by this update so we reuse
93 : * the original reference to the old value in the new
94 : * tuple.
95 : */
96 GIC 47 : ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
97 CBC 47 : continue;
98 ECB : }
99 : }
100 : }
101 : else
102 : {
103 : /*
104 : * For INSERT simply get the new value
105 : */
106 GIC 645192 : new_value = (struct varlena *) DatumGetPointer(ttc->ttc_values[i]);
107 ECB : }
108 :
109 : /*
110 : * Handle NULL attributes
111 : */
112 GIC 732496 : if (ttc->ttc_isnull[i])
113 ECB : {
114 GIC 75910 : ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
115 CBC 75910 : ttc->ttc_flags |= TOAST_HAS_NULLS;
116 75910 : continue;
117 ECB : }
118 :
119 : /*
120 : * Now look at varlena attributes
121 : */
122 GIC 656586 : if (att->attlen == -1)
123 ECB : {
124 : /*
125 : * If the table's attribute says PLAIN always, force it so.
126 : */
127 GIC 143621 : if (att->attstorage == TYPSTORAGE_PLAIN)
128 CBC 4902 : ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
129 ECB :
130 : /*
131 : * We took care of UPDATE above, so any external value we find
132 : * still in the tuple must be someone else's that we cannot reuse
133 : * (this includes the case of an out-of-line in-memory datum).
134 : * Fetch it back (without decompression, unless we are forcing
135 : * PLAIN storage). If necessary, we'll push it out as a new
136 : * external value below.
137 : */
138 GIC 143621 : if (VARATT_IS_EXTERNAL(new_value))
139 ECB : {
140 GIC 472 : ttc->ttc_attr[i].tai_oldexternal = new_value;
141 CBC 472 : if (att->attstorage == TYPSTORAGE_PLAIN)
142 LBC 0 : new_value = detoast_attr(new_value);
143 EUB : else
144 GIC 472 : new_value = detoast_external_attr(new_value);
145 CBC 472 : ttc->ttc_values[i] = PointerGetDatum(new_value);
146 472 : ttc->ttc_attr[i].tai_colflags |= TOASTCOL_NEEDS_FREE;
147 472 : ttc->ttc_flags |= (TOAST_NEEDS_CHANGE | TOAST_NEEDS_FREE);
148 ECB : }
149 :
150 : /*
151 : * Remember the size of this attribute
152 : */
153 GIC 143621 : ttc->ttc_attr[i].tai_size = VARSIZE_ANY(new_value);
154 ECB : }
155 : else
156 : {
157 : /*
158 : * Not a varlena attribute, plain storage always
159 : */
160 GIC 512965 : ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
161 ECB : }
162 : }
163 GIC 63963 : }
164 ECB :
165 : /*
166 : * Find the largest varlena attribute that satisfies certain criteria.
167 : *
168 : * The relevant column must not be marked TOASTCOL_IGNORE, and if the
169 : * for_compression flag is passed as true, it must also not be marked
170 : * TOASTCOL_INCOMPRESSIBLE.
171 : *
172 : * The column must have attstorage EXTERNAL or EXTENDED if check_main is
173 : * false, and must have attstorage MAIN if check_main is true.
174 : *
175 : * The column must have a minimum size of MAXALIGN(TOAST_POINTER_SIZE);
176 : * if not, no benefit is to be expected by compressing it.
177 : *
178 : * The return value is the index of the biggest suitable column, or
179 : * -1 if there is none.
180 : */
181 : int
182 GIC 77710 : toast_tuple_find_biggest_attribute(ToastTupleContext *ttc,
183 ECB : bool for_compression, bool check_main)
184 : {
185 GIC 77710 : TupleDesc tupleDesc = ttc->ttc_rel->rd_att;
186 CBC 77710 : int numAttrs = tupleDesc->natts;
187 77710 : int biggest_attno = -1;
188 77710 : int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE);
189 77710 : int32 skip_colflags = TOASTCOL_IGNORE;
190 ECB : int i;
191 :
192 GIC 77710 : if (for_compression)
193 CBC 74679 : skip_colflags |= TOASTCOL_INCOMPRESSIBLE;
194 ECB :
195 GIC 1158953 : for (i = 0; i < numAttrs; i++)
196 ECB : {
197 GIC 1081243 : Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
198 ECB :
199 GIC 1081243 : if ((ttc->ttc_attr[i].tai_colflags & skip_colflags) != 0)
200 CBC 893371 : continue;
201 187872 : if (VARATT_IS_EXTERNAL(DatumGetPointer(ttc->ttc_values[i])))
202 LBC 0 : continue; /* can't happen, toast_action would be PLAIN */
203 GBC 187872 : if (for_compression &&
204 CBC 179483 : VARATT_IS_COMPRESSED(DatumGetPointer(ttc->ttc_values[i])))
205 15612 : continue;
206 172260 : if (check_main && att->attstorage != TYPSTORAGE_MAIN)
207 LBC 0 : continue;
208 GBC 172260 : if (!check_main && att->attstorage != TYPSTORAGE_EXTENDED &&
209 CBC 2956 : att->attstorage != TYPSTORAGE_EXTERNAL)
210 56 : continue;
211 ECB :
212 GIC 172204 : if (ttc->ttc_attr[i].tai_size > biggest_size)
213 ECB : {
214 GIC 100285 : biggest_attno = i;
215 CBC 100285 : biggest_size = ttc->ttc_attr[i].tai_size;
216 ECB : }
217 : }
218 :
219 GIC 77710 : return biggest_attno;
220 ECB : }
221 :
222 : /*
223 : * Try compression for an attribute.
224 : *
225 : * If we find that the attribute is not compressible, mark it so.
226 : */
227 : void
228 GIC 68769 : toast_tuple_try_compression(ToastTupleContext *ttc, int attribute)
229 ECB : {
230 GIC 68769 : Datum *value = &ttc->ttc_values[attribute];
231 ECB : Datum new_value;
232 GIC 68769 : ToastAttrInfo *attr = &ttc->ttc_attr[attribute];
233 ECB :
234 GIC 68769 : new_value = toast_compress_datum(*value, attr->tai_compression);
235 ECB :
236 GIC 68769 : if (DatumGetPointer(new_value) != NULL)
237 ECB : {
238 : /* successful compression */
239 GIC 67221 : if ((attr->tai_colflags & TOASTCOL_NEEDS_FREE) != 0)
240 CBC 61 : pfree(DatumGetPointer(*value));
241 67221 : *value = new_value;
242 67221 : attr->tai_colflags |= TOASTCOL_NEEDS_FREE;
243 67221 : attr->tai_size = VARSIZE(DatumGetPointer(*value));
244 67221 : ttc->ttc_flags |= (TOAST_NEEDS_CHANGE | TOAST_NEEDS_FREE);
245 ECB : }
246 : else
247 : {
248 : /* incompressible, ignore on subsequent compression passes */
249 GIC 1548 : attr->tai_colflags |= TOASTCOL_INCOMPRESSIBLE;
250 ECB : }
251 GIC 68769 : }
252 ECB :
253 : /*
254 : * Move an attribute to external storage.
255 : */
256 : void
257 GIC 32344 : toast_tuple_externalize(ToastTupleContext *ttc, int attribute, int options)
258 ECB : {
259 GIC 32344 : Datum *value = &ttc->ttc_values[attribute];
260 CBC 32344 : Datum old_value = *value;
261 32344 : ToastAttrInfo *attr = &ttc->ttc_attr[attribute];
262 ECB :
263 GIC 32344 : attr->tai_colflags |= TOASTCOL_IGNORE;
264 CBC 32344 : *value = toast_save_datum(ttc->ttc_rel, old_value, attr->tai_oldexternal,
265 ECB : options);
266 GIC 32344 : if ((attr->tai_colflags & TOASTCOL_NEEDS_FREE) != 0)
267 CBC 29430 : pfree(DatumGetPointer(old_value));
268 32344 : attr->tai_colflags |= TOASTCOL_NEEDS_FREE;
269 32344 : ttc->ttc_flags |= (TOAST_NEEDS_CHANGE | TOAST_NEEDS_FREE);
270 32344 : }
271 ECB :
272 : /*
273 : * Perform appropriate cleanup after one tuple has been subjected to TOAST.
274 : */
275 : void
276 GIC 63963 : toast_tuple_cleanup(ToastTupleContext *ttc)
277 ECB : {
278 GIC 63963 : TupleDesc tupleDesc = ttc->ttc_rel->rd_att;
279 CBC 63963 : int numAttrs = tupleDesc->natts;
280 ECB :
281 : /*
282 : * Free allocated temp values
283 : */
284 GIC 63963 : if ((ttc->ttc_flags & TOAST_NEEDS_FREE) != 0)
285 ECB : {
286 : int i;
287 :
288 GIC 795670 : for (i = 0; i < numAttrs; i++)
289 ECB : {
290 GIC 731772 : ToastAttrInfo *attr = &ttc->ttc_attr[i];
291 ECB :
292 GIC 731772 : if ((attr->tai_colflags & TOASTCOL_NEEDS_FREE) != 0)
293 CBC 70546 : pfree(DatumGetPointer(ttc->ttc_values[i]));
294 ECB : }
295 : }
296 :
297 : /*
298 : * Delete external values from the old tuple
299 : */
300 GIC 63963 : if ((ttc->ttc_flags & TOAST_NEEDS_DELETE_OLD) != 0)
301 ECB : {
302 : int i;
303 :
304 GIC 4506 : for (i = 0; i < numAttrs; i++)
305 ECB : {
306 GIC 4321 : ToastAttrInfo *attr = &ttc->ttc_attr[i];
307 ECB :
308 GIC 4321 : if ((attr->tai_colflags & TOASTCOL_NEEDS_DELETE_OLD) != 0)
309 CBC 214 : toast_delete_datum(ttc->ttc_rel, ttc->ttc_oldvalues[i], false);
310 ECB : }
311 : }
312 GIC 63963 : }
313 ECB :
314 : /*
315 : * Check for external stored attributes and delete them from the secondary
316 : * relation.
317 : */
318 : void
319 GIC 234 : toast_delete_external(Relation rel, Datum *values, bool *isnull,
320 ECB : bool is_speculative)
321 : {
322 GIC 234 : TupleDesc tupleDesc = rel->rd_att;
323 CBC 234 : int numAttrs = tupleDesc->natts;
324 ECB : int i;
325 :
326 GIC 1540 : for (i = 0; i < numAttrs; i++)
327 ECB : {
328 GIC 1306 : if (TupleDescAttr(tupleDesc, i)->attlen == -1)
329 ECB : {
330 GIC 472 : Datum value = values[i];
331 ECB :
332 GIC 472 : if (isnull[i])
333 CBC 126 : continue;
334 GNC 346 : else if (VARATT_IS_EXTERNAL_ONDISK(value))
335 CBC 244 : toast_delete_datum(rel, value, is_speculative);
336 ECB : }
337 : }
338 GIC 234 : }
|
