PostgreSQL Source Code: src/backend/optimizer/geqo/geqo_main.c Source File

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geqo_main.c
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1/*------------------------------------------------------------------------
2 *
3 * geqo_main.c
4 * solution to the query optimization problem
5 * by means of a Genetic Algorithm (GA)
6 *
7 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
9 *
10 * src/backend/optimizer/geqo/geqo_main.c
11 *
12 *-------------------------------------------------------------------------
13 */
14
15/* contributed by:
16 =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
17 * Martin Utesch * Institute of Automatic Control *
18 = = University of Mining and Technology =
19 * utesch@aut.tu-freiberg.de * Freiberg, Germany *
20 =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
21 */
22
23/* -- parts of this are adapted from D. Whitley's Genitor algorithm -- */
24
25#include "postgres.h"
26
27#include <math.h>
28
29#include "optimizer/geqo.h"
30
31#include "optimizer/geqo_misc.h"
32#if defined(CX)
33#include "optimizer/geqo_mutation.h"
34#endif
35#include "optimizer/geqo_pool.h"
36#include "optimizer/geqo_random.h"
37#include "optimizer/geqo_recombination.h"
38#include "optimizer/geqo_selection.h"
39
40
41/*
42 * Configuration options
43 */
44 int Geqo_effort;
45 int Geqo_pool_size;
46 int Geqo_generations;
47 double Geqo_selection_bias;
48 double Geqo_seed;
49
50
51static int gimme_pool_size(int nr_rel);
52static int gimme_number_generations(int pool_size);
53
54/* complain if no recombination mechanism is #define'd */
55#if !defined(ERX) && \
56 !defined(PMX) && \
57 !defined(CX) && \
58 !defined(PX) && \
59 !defined(OX1) && \
60 !defined(OX2)
61#error "must choose one GEQO recombination mechanism in geqo.h"
62#endif
63
64
65/*
66 * geqo
67 * solution of the query optimization problem
68 * similar to a constrained Traveling Salesman Problem (TSP)
69 */
70
71RelOptInfo *
72 geqo(PlannerInfo *root, int number_of_rels, List *initial_rels)
73{
74 GeqoPrivateData private;
75 int generation;
76 Chromosome *momma;
77 Chromosome *daddy;
78 Chromosome *kid;
79 Pool *pool;
80 int pool_size,
81 number_generations;
82
83#ifdef GEQO_DEBUG
84 int status_interval;
85#endif
86 Gene *best_tour;
87 RelOptInfo *best_rel;
88
89#if defined(ERX)
90 Edge *edge_table; /* list of edges */
91 int edge_failures = 0;
92#endif
93#if defined(CX) || defined(PX) || defined(OX1) || defined(OX2)
94 City *city_table; /* list of cities */
95#endif
96#if defined(CX)
97 int cycle_diffs = 0;
98 int mutations = 0;
99#endif
100
101/* set up private information */
102 root->join_search_private = &private;
103 private.initial_rels = initial_rels;
104
105/* initialize private number generator */
106 geqo_set_seed(root, Geqo_seed);
107
108/* set GA parameters */
109 pool_size = gimme_pool_size(number_of_rels);
110 number_generations = gimme_number_generations(pool_size);
111#ifdef GEQO_DEBUG
112 status_interval = 10;
113#endif
114
115/* allocate genetic pool memory */
116 pool = alloc_pool(root, pool_size, number_of_rels);
117
118/* random initialization of the pool */
119 random_init_pool(root, pool);
120
121/* sort the pool according to cheapest path as fitness */
122 sort_pool(root, pool); /* we have to do it only one time, since all
123 * kids replace the worst individuals in
124 * future (-> geqo_pool.c:spread_chromo ) */
125
126#ifdef GEQO_DEBUG
127 elog(DEBUG1, "GEQO selected %d pool entries, best %.2f, worst %.2f",
128 pool_size,
129 pool->data[0].worth,
130 pool->data[pool_size - 1].worth);
131#endif
132
133/* allocate chromosome momma and daddy memory */
134 momma = alloc_chromo(root, pool->string_length);
135 daddy = alloc_chromo(root, pool->string_length);
136
137#if defined (ERX)
138#ifdef GEQO_DEBUG
139 elog(DEBUG2, "using edge recombination crossover [ERX]");
140#endif
141/* allocate edge table memory */
142 edge_table = alloc_edge_table(root, pool->string_length);
143#elif defined(PMX)
144#ifdef GEQO_DEBUG
145 elog(DEBUG2, "using partially matched crossover [PMX]");
146#endif
147/* allocate chromosome kid memory */
148 kid = alloc_chromo(root, pool->string_length);
149#elif defined(CX)
150#ifdef GEQO_DEBUG
151 elog(DEBUG2, "using cycle crossover [CX]");
152#endif
153/* allocate city table memory */
154 kid = alloc_chromo(root, pool->string_length);
155 city_table = alloc_city_table(root, pool->string_length);
156#elif defined(PX)
157#ifdef GEQO_DEBUG
158 elog(DEBUG2, "using position crossover [PX]");
159#endif
160/* allocate city table memory */
161 kid = alloc_chromo(root, pool->string_length);
162 city_table = alloc_city_table(root, pool->string_length);
163#elif defined(OX1)
164#ifdef GEQO_DEBUG
165 elog(DEBUG2, "using order crossover [OX1]");
166#endif
167/* allocate city table memory */
168 kid = alloc_chromo(root, pool->string_length);
169 city_table = alloc_city_table(root, pool->string_length);
170#elif defined(OX2)
171#ifdef GEQO_DEBUG
172 elog(DEBUG2, "using order crossover [OX2]");
173#endif
174/* allocate city table memory */
175 kid = alloc_chromo(root, pool->string_length);
176 city_table = alloc_city_table(root, pool->string_length);
177#endif
178
179
180/* my pain main part: */
181/* iterative optimization */
182
183 for (generation = 0; generation < number_generations; generation++)
184 {
185 /* SELECTION: using linear bias function */
186 geqo_selection(root, momma, daddy, pool, Geqo_selection_bias);
187
188#if defined (ERX)
189 /* EDGE RECOMBINATION CROSSOVER */
190 gimme_edge_table(root, momma->string, daddy->string, pool->string_length, edge_table);
191
192 kid = momma;
193
194 /* are there any edge failures ? */
195 edge_failures += gimme_tour(root, edge_table, kid->string, pool->string_length);
196#elif defined(PMX)
197 /* PARTIALLY MATCHED CROSSOVER */
198 pmx(root, momma->string, daddy->string, kid->string, pool->string_length);
199#elif defined(CX)
200 /* CYCLE CROSSOVER */
201 cycle_diffs = cx(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
202 /* mutate the child */
203 if (cycle_diffs == 0)
204 {
205 mutations++;
206 geqo_mutation(root, kid->string, pool->string_length);
207 }
208#elif defined(PX)
209 /* POSITION CROSSOVER */
210 px(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
211#elif defined(OX1)
212 /* ORDER CROSSOVER */
213 ox1(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
214#elif defined(OX2)
215 /* ORDER CROSSOVER */
216 ox2(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
217#endif
218
219
220 /* EVALUATE FITNESS */
221 kid->worth = geqo_eval(root, kid->string, pool->string_length);
222
223 /* push the kid into the wilderness of life according to its worth */
224 spread_chromo(root, kid, pool);
225
226
227#ifdef GEQO_DEBUG
228 if (status_interval && !(generation % status_interval))
229 print_gen(stdout, pool, generation);
230#endif
231
232 }
233
234
235#if defined(ERX)
236#if defined(GEQO_DEBUG)
237 if (edge_failures != 0)
238 elog(LOG, "[GEQO] failures: %d, average: %d",
239 edge_failures, (int) number_generations / edge_failures);
240 else
241 elog(LOG, "[GEQO] no edge failures detected");
242#else
243 /* suppress variable-set-but-not-used warnings from some compilers */
244 (void) edge_failures;
245#endif
246#endif
247
248#if defined(CX) && defined(GEQO_DEBUG)
249 if (mutations != 0)
250 elog(LOG, "[GEQO] mutations: %d, generations: %d",
251 mutations, number_generations);
252 else
253 elog(LOG, "[GEQO] no mutations processed");
254#endif
255
256#ifdef GEQO_DEBUG
257 print_pool(stdout, pool, 0, pool_size - 1);
258#endif
259
260#ifdef GEQO_DEBUG
261 elog(DEBUG1, "GEQO best is %.2f after %d generations",
262 pool->data[0].worth, number_generations);
263#endif
264
265
266 /*
267 * got the cheapest query tree processed by geqo; first element of the
268 * population indicates the best query tree
269 */
270 best_tour = (Gene *) pool->data[0].string;
271
272 best_rel = gimme_tree(root, best_tour, pool->string_length);
273
274 if (best_rel == NULL)
275 elog(ERROR, "geqo failed to make a valid plan");
276
277 /* DBG: show the query plan */
278#ifdef NOT_USED
279 print_plan(best_plan, root);
280#endif
281
282 /* ... free memory stuff */
283 free_chromo(root, momma);
284 free_chromo(root, daddy);
285
286#if defined (ERX)
287 free_edge_table(root, edge_table);
288#elif defined(PMX)
289 free_chromo(root, kid);
290#elif defined(CX)
291 free_chromo(root, kid);
292 free_city_table(root, city_table);
293#elif defined(PX)
294 free_chromo(root, kid);
295 free_city_table(root, city_table);
296#elif defined(OX1)
297 free_chromo(root, kid);
298 free_city_table(root, city_table);
299#elif defined(OX2)
300 free_chromo(root, kid);
301 free_city_table(root, city_table);
302#endif
303
304 free_pool(root, pool);
305
306 /* ... clear root pointer to our private storage */
307 root->join_search_private = NULL;
308
309 return best_rel;
310}
311
312
313/*
314 * Return either configured pool size or a good default
315 *
316 * The default is based on query size (no. of relations) = 2^(QS+1),
317 * but constrained to a range based on the effort value.
318 */
319static int
320 gimme_pool_size(int nr_rel)
321{
322 double size;
323 int minsize;
324 int maxsize;
325
326 /* Legal pool size *must* be at least 2, so ignore attempt to select 1 */
327 if (Geqo_pool_size >= 2)
328 return Geqo_pool_size;
329
330 size = pow(2.0, nr_rel + 1.0);
331
332 maxsize = 50 * Geqo_effort; /* 50 to 500 individuals */
333 if (size > maxsize)
334 return maxsize;
335
336 minsize = 10 * Geqo_effort; /* 10 to 100 individuals */
337 if (size < minsize)
338 return minsize;
339
340 return (int) ceil(size);
341}
342
343
344/*
345 * Return either configured number of generations or a good default
346 *
347 * The default is the same as the pool size, which allows us to be
348 * sure that less-fit individuals get pushed out of the breeding
349 * population before the run finishes.
350 */
351static int
352 gimme_number_generations(int pool_size)
353{
354 if (Geqo_generations > 0)
355 return Geqo_generations;
356
357 return pool_size;
358}
#define LOG
Definition: elog.h:31
#define DEBUG2
Definition: elog.h:29
#define DEBUG1
Definition: elog.h:30
#define ERROR
Definition: elog.h:39
#define elog(elevel,...)
Definition: elog.h:226
Edge * alloc_edge_table(PlannerInfo *root, int num_gene)
Definition: geqo_erx.c:56
float gimme_edge_table(PlannerInfo *root, Gene *tour1, Gene *tour2, int num_gene, Edge *edge_table)
Definition: geqo_erx.c:95
void free_edge_table(PlannerInfo *root, Edge *edge_table)
Definition: geqo_erx.c:76
int gimme_tour(PlannerInfo *root, Edge *edge_table, Gene *new_gene, int num_gene)
Definition: geqo_erx.c:196
Cost geqo_eval(PlannerInfo *root, Gene *tour, int num_gene)
Definition: geqo_eval.c:57
RelOptInfo * gimme_tree(PlannerInfo *root, Gene *tour, int num_gene)
Definition: geqo_eval.c:163
int Gene
Definition: geqo_gene.h:30
int Geqo_pool_size
Definition: geqo_main.c:45
double Geqo_seed
Definition: geqo_main.c:48
int Geqo_generations
Definition: geqo_main.c:46
RelOptInfo * geqo(PlannerInfo *root, int number_of_rels, List *initial_rels)
Definition: geqo_main.c:72
static int gimme_number_generations(int pool_size)
Definition: geqo_main.c:352
static int gimme_pool_size(int nr_rel)
Definition: geqo_main.c:320
int Geqo_effort
Definition: geqo_main.c:44
double Geqo_selection_bias
Definition: geqo_main.c:47
void geqo_mutation(PlannerInfo *root, Gene *tour, int num_gene)
Pool * alloc_pool(PlannerInfo *root, int pool_size, int string_length)
Definition: geqo_pool.c:42
void sort_pool(PlannerInfo *root, Pool *pool)
Definition: geqo_pool.c:135
void free_chromo(PlannerInfo *root, Chromosome *chromo)
Definition: geqo_pool.c:176
void free_pool(PlannerInfo *root, Pool *pool)
Definition: geqo_pool.c:69
void random_init_pool(PlannerInfo *root, Pool *pool)
Definition: geqo_pool.c:91
void spread_chromo(PlannerInfo *root, Chromosome *chromo, Pool *pool)
Definition: geqo_pool.c:187
Chromosome * alloc_chromo(PlannerInfo *root, int string_length)
Definition: geqo_pool.c:162
void geqo_set_seed(PlannerInfo *root, double seed)
Definition: geqo_random.c:20
void free_city_table(PlannerInfo *root, City *city_table)
void pmx(PlannerInfo *root, Gene *tour1, Gene *tour2, Gene *offspring, int num_gene)
City * alloc_city_table(PlannerInfo *root, int num_gene)
void ox1(PlannerInfo *root, Gene *mom, Gene *dad, Gene *offspring, int num_gene, City *city_table)
int cx(PlannerInfo *root, Gene *tour1, Gene *tour2, Gene *offspring, int num_gene, City *city_table)
void ox2(PlannerInfo *root, Gene *mom, Gene *dad, Gene *offspring, int num_gene, City *city_table)
void px(PlannerInfo *root, Gene *tour1, Gene *tour2, Gene *offspring, int num_gene, City *city_table)
void geqo_selection(PlannerInfo *root, Chromosome *momma, Chromosome *daddy, Pool *pool, double bias)
Definition: geqo_selection.c:54
stdout
tree ctl root
Definition: radixtree.h:1857
Cost worth
Definition: geqo_gene.h:35
Gene * string
Definition: geqo_gene.h:34
Definition: pg_list.h:54
Definition: geqo_gene.h:39
int string_length
Definition: geqo_gene.h:42
Chromosome * data
Definition: geqo_gene.h:40

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