Line data Source code
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) 1996-2017, 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_misc.h"
30 : #include "optimizer/geqo_mutation.h"
31 : #include "optimizer/geqo_pool.h"
32 : #include "optimizer/geqo_random.h"
33 : #include "optimizer/geqo_selection.h"
34 :
35 :
36 : /*
37 : * Configuration options
38 : */
39 : int Geqo_effort;
40 : int Geqo_pool_size;
41 : int Geqo_generations;
42 : double Geqo_selection_bias;
43 : double Geqo_seed;
44 :
45 :
46 : static int gimme_pool_size(int nr_rel);
47 : static int gimme_number_generations(int pool_size);
48 :
49 : /* complain if no recombination mechanism is #define'd */
50 : #if !defined(ERX) && \
51 : !defined(PMX) && \
52 : !defined(CX) && \
53 : !defined(PX) && \
54 : !defined(OX1) && \
55 : !defined(OX2)
56 : #error "must choose one GEQO recombination mechanism in geqo.h"
57 : #endif
58 :
59 :
60 : /*
61 : * geqo
62 : * solution of the query optimization problem
63 : * similar to a constrained Traveling Salesman Problem (TSP)
64 : */
65 :
66 : RelOptInfo *
67 1 : geqo(PlannerInfo *root, int number_of_rels, List *initial_rels)
68 : {
69 : GeqoPrivateData private;
70 : int generation;
71 : Chromosome *momma;
72 : Chromosome *daddy;
73 : Chromosome *kid;
74 : Pool *pool;
75 : int pool_size,
76 : number_generations;
77 :
78 : #ifdef GEQO_DEBUG
79 : int status_interval;
80 : #endif
81 : Gene *best_tour;
82 : RelOptInfo *best_rel;
83 :
84 : #if defined(ERX)
85 : Edge *edge_table; /* list of edges */
86 1 : int edge_failures = 0;
87 : #endif
88 : #if defined(CX) || defined(PX) || defined(OX1) || defined(OX2)
89 : City *city_table; /* list of cities */
90 : #endif
91 : #if defined(CX)
92 : int cycle_diffs = 0;
93 : int mutations = 0;
94 : #endif
95 :
96 : /* set up private information */
97 1 : root->join_search_private = (void *) &private;
98 1 : private.initial_rels = initial_rels;
99 :
100 : /* initialize private number generator */
101 1 : geqo_set_seed(root, Geqo_seed);
102 :
103 : /* set GA parameters */
104 1 : pool_size = gimme_pool_size(number_of_rels);
105 1 : number_generations = gimme_number_generations(pool_size);
106 : #ifdef GEQO_DEBUG
107 : status_interval = 10;
108 : #endif
109 :
110 : /* allocate genetic pool memory */
111 1 : pool = alloc_pool(root, pool_size, number_of_rels);
112 :
113 : /* random initialization of the pool */
114 1 : random_init_pool(root, pool);
115 :
116 : /* sort the pool according to cheapest path as fitness */
117 1 : sort_pool(root, pool); /* we have to do it only one time, since all
118 : * kids replace the worst individuals in
119 : * future (-> geqo_pool.c:spread_chromo ) */
120 :
121 : #ifdef GEQO_DEBUG
122 : elog(DEBUG1, "GEQO selected %d pool entries, best %.2f, worst %.2f",
123 : pool_size,
124 : pool->data[0].worth,
125 : pool->data[pool_size - 1].worth);
126 : #endif
127 :
128 : /* allocate chromosome momma and daddy memory */
129 1 : momma = alloc_chromo(root, pool->string_length);
130 1 : daddy = alloc_chromo(root, pool->string_length);
131 :
132 : #if defined (ERX)
133 : #ifdef GEQO_DEBUG
134 : elog(DEBUG2, "using edge recombination crossover [ERX]");
135 : #endif
136 : /* allocate edge table memory */
137 1 : edge_table = alloc_edge_table(root, pool->string_length);
138 : #elif defined(PMX)
139 : #ifdef GEQO_DEBUG
140 : elog(DEBUG2, "using partially matched crossover [PMX]");
141 : #endif
142 : /* allocate chromosome kid memory */
143 : kid = alloc_chromo(root, pool->string_length);
144 : #elif defined(CX)
145 : #ifdef GEQO_DEBUG
146 : elog(DEBUG2, "using cycle crossover [CX]");
147 : #endif
148 : /* allocate city table memory */
149 : kid = alloc_chromo(root, pool->string_length);
150 : city_table = alloc_city_table(root, pool->string_length);
151 : #elif defined(PX)
152 : #ifdef GEQO_DEBUG
153 : elog(DEBUG2, "using position crossover [PX]");
154 : #endif
155 : /* allocate city table memory */
156 : kid = alloc_chromo(root, pool->string_length);
157 : city_table = alloc_city_table(root, pool->string_length);
158 : #elif defined(OX1)
159 : #ifdef GEQO_DEBUG
160 : elog(DEBUG2, "using order crossover [OX1]");
161 : #endif
162 : /* allocate city table memory */
163 : kid = alloc_chromo(root, pool->string_length);
164 : city_table = alloc_city_table(root, pool->string_length);
165 : #elif defined(OX2)
166 : #ifdef GEQO_DEBUG
167 : elog(DEBUG2, "using order crossover [OX2]");
168 : #endif
169 : /* allocate city table memory */
170 : kid = alloc_chromo(root, pool->string_length);
171 : city_table = alloc_city_table(root, pool->string_length);
172 : #endif
173 :
174 :
175 : /* my pain main part: */
176 : /* iterative optimization */
177 :
178 65 : for (generation = 0; generation < number_generations; generation++)
179 : {
180 : /* SELECTION: using linear bias function */
181 64 : geqo_selection(root, momma, daddy, pool, Geqo_selection_bias);
182 :
183 : #if defined (ERX)
184 : /* EDGE RECOMBINATION CROSSOVER */
185 64 : gimme_edge_table(root, momma->string, daddy->string, pool->string_length, edge_table);
186 :
187 64 : kid = momma;
188 :
189 : /* are there any edge failures ? */
190 64 : edge_failures += gimme_tour(root, edge_table, kid->string, pool->string_length);
191 : #elif defined(PMX)
192 : /* PARTIALLY MATCHED CROSSOVER */
193 : pmx(root, momma->string, daddy->string, kid->string, pool->string_length);
194 : #elif defined(CX)
195 : /* CYCLE CROSSOVER */
196 : cycle_diffs = cx(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
197 : /* mutate the child */
198 : if (cycle_diffs == 0)
199 : {
200 : mutations++;
201 : geqo_mutation(root, kid->string, pool->string_length);
202 : }
203 : #elif defined(PX)
204 : /* POSITION CROSSOVER */
205 : px(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
206 : #elif defined(OX1)
207 : /* ORDER CROSSOVER */
208 : ox1(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
209 : #elif defined(OX2)
210 : /* ORDER CROSSOVER */
211 : ox2(root, momma->string, daddy->string, kid->string, pool->string_length, city_table);
212 : #endif
213 :
214 :
215 : /* EVALUATE FITNESS */
216 64 : kid->worth = geqo_eval(root, kid->string, pool->string_length);
217 :
218 : /* push the kid into the wilderness of life according to its worth */
219 64 : spread_chromo(root, kid, pool);
220 :
221 :
222 : #ifdef GEQO_DEBUG
223 : if (status_interval && !(generation % status_interval))
224 : print_gen(stdout, pool, generation);
225 : #endif
226 :
227 : }
228 :
229 :
230 : #if defined(ERX) && defined(GEQO_DEBUG)
231 : if (edge_failures != 0)
232 : elog(LOG, "[GEQO] failures: %d, average: %d",
233 : edge_failures, (int) number_generations / edge_failures);
234 : else
235 : elog(LOG, "[GEQO] no edge failures detected");
236 : #endif
237 :
238 : #if defined(CX) && defined(GEQO_DEBUG)
239 : if (mutations != 0)
240 : elog(LOG, "[GEQO] mutations: %d, generations: %d",
241 : mutations, number_generations);
242 : else
243 : elog(LOG, "[GEQO] no mutations processed");
244 : #endif
245 :
246 : #ifdef GEQO_DEBUG
247 : print_pool(stdout, pool, 0, pool_size - 1);
248 : #endif
249 :
250 : #ifdef GEQO_DEBUG
251 : elog(DEBUG1, "GEQO best is %.2f after %d generations",
252 : pool->data[0].worth, number_generations);
253 : #endif
254 :
255 :
256 : /*
257 : * got the cheapest query tree processed by geqo; first element of the
258 : * population indicates the best query tree
259 : */
260 1 : best_tour = (Gene *) pool->data[0].string;
261 :
262 1 : best_rel = gimme_tree(root, best_tour, pool->string_length);
263 :
264 1 : if (best_rel == NULL)
265 0 : elog(ERROR, "geqo failed to make a valid plan");
266 :
267 : /* DBG: show the query plan */
268 : #ifdef NOT_USED
269 : print_plan(best_plan, root);
270 : #endif
271 :
272 : /* ... free memory stuff */
273 1 : free_chromo(root, momma);
274 1 : free_chromo(root, daddy);
275 :
276 : #if defined (ERX)
277 1 : free_edge_table(root, edge_table);
278 : #elif defined(PMX)
279 : free_chromo(root, kid);
280 : #elif defined(CX)
281 : free_chromo(root, kid);
282 : free_city_table(root, city_table);
283 : #elif defined(PX)
284 : free_chromo(root, kid);
285 : free_city_table(root, city_table);
286 : #elif defined(OX1)
287 : free_chromo(root, kid);
288 : free_city_table(root, city_table);
289 : #elif defined(OX2)
290 : free_chromo(root, kid);
291 : free_city_table(root, city_table);
292 : #endif
293 :
294 1 : free_pool(root, pool);
295 :
296 : /* ... clear root pointer to our private storage */
297 1 : root->join_search_private = NULL;
298 :
299 1 : return best_rel;
300 : }
301 :
302 :
303 : /*
304 : * Return either configured pool size or a good default
305 : *
306 : * The default is based on query size (no. of relations) = 2^(QS+1),
307 : * but constrained to a range based on the effort value.
308 : */
309 : static int
310 1 : gimme_pool_size(int nr_rel)
311 : {
312 : double size;
313 : int minsize;
314 : int maxsize;
315 :
316 : /* Legal pool size *must* be at least 2, so ignore attempt to select 1 */
317 1 : if (Geqo_pool_size >= 2)
318 0 : return Geqo_pool_size;
319 :
320 1 : size = pow(2.0, nr_rel + 1.0);
321 :
322 1 : maxsize = 50 * Geqo_effort; /* 50 to 500 individuals */
323 1 : if (size > maxsize)
324 0 : return maxsize;
325 :
326 1 : minsize = 10 * Geqo_effort; /* 10 to 100 individuals */
327 1 : if (size < minsize)
328 0 : return minsize;
329 :
330 1 : return (int) ceil(size);
331 : }
332 :
333 :
334 : /*
335 : * Return either configured number of generations or a good default
336 : *
337 : * The default is the same as the pool size, which allows us to be
338 : * sure that less-fit individuals get pushed out of the breeding
339 : * population before the run finishes.
340 : */
341 : static int
342 1 : gimme_number_generations(int pool_size)
343 : {
344 1 : if (Geqo_generations > 0)
345 0 : return Geqo_generations;
346 :
347 1 : return pool_size;
348 : }
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