1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
|
# frozen_string_literal: true
module Gitlab
module Database
module Migrations
module ConstraintsHelpers
include LockRetriesHelpers
include TimeoutHelpers
# https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
MAX_IDENTIFIER_NAME_LENGTH = 63
# Returns the name for a check constraint
#
# type:
# - Any value, as long as it is unique
# - Constraint names are unique per table in Postgres, and, additionally,
# we can have multiple check constraints over a column
# So we use the (table, column, type) triplet as a unique name
# - e.g. we use 'max_length' when adding checks for text limits
# or 'not_null' when adding a NOT NULL constraint
#
def check_constraint_name(table, column, type)
identifier = "#{table}_#{column}_check_#{type}"
# Check concurrent_foreign_key_name() for info on why we use a hash
hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10)
"check_#{hashed_identifier}"
end
def check_constraint_exists?(table, constraint_name)
# Constraint names are unique per table in Postgres, not per schema
# Two tables can have constraints with the same name, so we filter by
# the table name in addition to using the constraint_name
check_sql = <<~SQL
SELECT COUNT(*)
FROM pg_catalog.pg_constraint con
INNER JOIN pg_catalog.pg_class rel
ON rel.oid = con.conrelid
INNER JOIN pg_catalog.pg_namespace nsp
ON nsp.oid = con.connamespace
WHERE con.contype = 'c'
AND con.conname = #{connection.quote(constraint_name)}
AND nsp.nspname = #{connection.quote(current_schema)}
AND rel.relname = #{connection.quote(table)}
SQL
connection.select_value(check_sql) > 0
end
# Adds a check constraint to a table
#
# This method is the generic helper for adding any check constraint
# More specialized helpers may use it (e.g. add_text_limit or add_not_null)
#
# This method only requires minimal locking:
# - The constraint is added using NOT VALID
# This allows us to add the check constraint without validating it
# - The check will be enforced for new data (inserts) coming in
# - If `validate: true` the constraint is also validated
# Otherwise, validate_check_constraint() can be used at a later stage
# - Check comments on add_concurrent_foreign_key for more info
#
# table - The table the constraint will be added to
# check - The check clause to add
# e.g. 'char_length(name) <= 5' or 'store IS NOT NULL'
# constraint_name - The name of the check constraint (otherwise auto-generated)
# Should be unique per table (not per column)
# validate - Whether to validate the constraint in this call
#
def add_check_constraint(table, check, constraint_name, validate: true)
# Transactions would result in ALTER TABLE locks being held for the
# duration of the transaction, defeating the purpose of this method.
validate_not_in_transaction!(:add_check_constraint)
validate_check_constraint_name!(constraint_name)
if check_constraint_exists?(table, constraint_name)
warning_message = <<~MESSAGE
Check constraint was not created because it exists already
(this may be due to an aborted migration or similar)
table: #{table}, check: #{check}, constraint name: #{constraint_name}
MESSAGE
Gitlab::AppLogger.warn warning_message
else
# Only add the constraint without validating it
# Even though it is fast, ADD CONSTRAINT requires an EXCLUSIVE lock
# Use with_lock_retries to make sure that this operation
# will not timeout on tables accessed by many processes
with_lock_retries do
execute <<~SQL
ALTER TABLE #{table}
ADD CONSTRAINT #{constraint_name}
CHECK ( #{check} )
NOT VALID;
SQL
end
end
validate_check_constraint(table, constraint_name) if validate
end
def validate_check_constraint(table, constraint_name)
validate_check_constraint_name!(constraint_name)
unless check_constraint_exists?(table, constraint_name)
raise missing_schema_object_message(table, "check constraint", constraint_name)
end
disable_statement_timeout do
# VALIDATE CONSTRAINT only requires a SHARE UPDATE EXCLUSIVE LOCK
# It only conflicts with other validations and creating indexes
execute("ALTER TABLE #{table} VALIDATE CONSTRAINT #{constraint_name};")
end
end
def remove_check_constraint(table, constraint_name)
# This is technically not necessary, but aligned with add_check_constraint
# and allows us to continue use with_lock_retries here
validate_not_in_transaction!(:remove_check_constraint)
validate_check_constraint_name!(constraint_name)
# DROP CONSTRAINT requires an EXCLUSIVE lock
# Use with_lock_retries to make sure that this will not timeout
with_lock_retries do
execute <<-SQL
ALTER TABLE #{table}
DROP CONSTRAINT IF EXISTS #{constraint_name}
SQL
end
end
# Copies all check constraints for the old column to the new column.
#
# table - The table containing the columns.
# old - The old column.
# new - The new column.
# schema - The schema the table is defined for
# If it is not provided, then the current_schema is used
def copy_check_constraints(table, old, new, schema: nil)
raise 'copy_check_constraints can not be run inside a transaction' if transaction_open?
raise "Column #{old} does not exist on #{table}" unless column_exists?(table, old)
raise "Column #{new} does not exist on #{table}" unless column_exists?(table, new)
table_with_schema = schema.present? ? "#{schema}.#{table}" : table
check_constraints_for(table, old, schema: schema).each do |check_c|
validate = !(check_c["constraint_def"].end_with? "NOT VALID")
# Normalize:
# - Old constraint definitions:
# '(char_length(entity_path) <= 5500)'
# - Definitionss from pg_get_constraintdef(oid):
# 'CHECK ((char_length(entity_path) <= 5500))'
# - Definitions from pg_get_constraintdef(oid, pretty_bool):
# 'CHECK (char_length(entity_path) <= 5500)'
# - Not valid constraints: 'CHECK (...) NOT VALID'
# to a single format that we can use:
# '(char_length(entity_path) <= 5500)'
check_definition = check_c["constraint_def"]
.sub(/^\s*(CHECK)?\s*\({0,2}/, '(')
.sub(/\){0,2}\s*(NOT VALID)?\s*$/, ')')
constraint_name = if check_definition == "(#{old} IS NOT NULL)"
not_null_constraint_name(table_with_schema, new)
elsif check_definition.start_with? "(char_length(#{old}) <="
text_limit_name(table_with_schema, new)
else
check_constraint_name(table_with_schema, new, 'copy_check_constraint')
end
add_check_constraint(
table_with_schema,
check_definition.gsub(old.to_s, new.to_s),
constraint_name,
validate: validate
)
end
end
# Migration Helpers for adding limit to text columns
def add_text_limit(table, column, limit, constraint_name: nil, validate: true)
add_check_constraint(
table,
"char_length(#{column}) <= #{limit}",
text_limit_name(table, column, name: constraint_name),
validate: validate
)
end
def validate_text_limit(table, column, constraint_name: nil)
validate_check_constraint(table, text_limit_name(table, column, name: constraint_name))
end
def remove_text_limit(table, column, constraint_name: nil)
remove_check_constraint(table, text_limit_name(table, column, name: constraint_name))
end
def check_text_limit_exists?(table, column, constraint_name: nil)
check_constraint_exists?(table, text_limit_name(table, column, name: constraint_name))
end
# Migration Helpers for managing not null constraints
def add_not_null_constraint(table, column, constraint_name: nil, validate: true)
if column_is_nullable?(table, column)
add_check_constraint(
table,
"#{column} IS NOT NULL",
not_null_constraint_name(table, column, name: constraint_name),
validate: validate
)
else
warning_message = <<~MESSAGE
NOT NULL check constraint was not created:
column #{table}.#{column} is already defined as `NOT NULL`
MESSAGE
Gitlab::AppLogger.warn warning_message
end
end
def validate_not_null_constraint(table, column, constraint_name: nil)
validate_check_constraint(
table,
not_null_constraint_name(table, column, name: constraint_name)
)
end
def remove_not_null_constraint(table, column, constraint_name: nil)
remove_check_constraint(
table,
not_null_constraint_name(table, column, name: constraint_name)
)
end
def check_not_null_constraint_exists?(table, column, constraint_name: nil)
check_constraint_exists?(
table,
not_null_constraint_name(table, column, name: constraint_name)
)
end
def rename_constraint(table_name, old_name, new_name)
execute <<~SQL
ALTER TABLE #{quote_table_name(table_name)}
RENAME CONSTRAINT #{quote_column_name(old_name)} TO #{quote_column_name(new_name)}
SQL
end
def drop_constraint(table_name, constraint_name, cascade: false)
execute <<~SQL
ALTER TABLE #{quote_table_name(table_name)} DROP CONSTRAINT #{quote_column_name(constraint_name)} #{cascade_statement(cascade)}
SQL
end
def validate_check_constraint_name!(constraint_name)
return unless constraint_name.to_s.length > MAX_IDENTIFIER_NAME_LENGTH
raise "The maximum allowed constraint name is #{MAX_IDENTIFIER_NAME_LENGTH} characters"
end
def text_limit_name(table, column, name: nil)
name.presence || check_constraint_name(table, column, 'max_length')
end
private
def validate_not_in_transaction!(method_name, modifier = nil)
return unless transaction_open?
raise <<~ERROR
#{["`#{method_name}`", modifier].compact.join(' ')} cannot be run inside a transaction.
You can disable transactions by calling `disable_ddl_transaction!` in the body of
your migration class
ERROR
end
# Returns an ActiveRecord::Result containing the check constraints
# defined for the given column.
#
# If the schema is not provided, then the current_schema is used
def check_constraints_for(table, column, schema: nil)
check_sql = <<~SQL
SELECT
ccu.table_schema as schema_name,
ccu.table_name as table_name,
ccu.column_name as column_name,
con.conname as constraint_name,
pg_get_constraintdef(con.oid) as constraint_def
FROM pg_catalog.pg_constraint con
INNER JOIN pg_catalog.pg_class rel
ON rel.oid = con.conrelid
INNER JOIN pg_catalog.pg_namespace nsp
ON nsp.oid = con.connamespace
INNER JOIN information_schema.constraint_column_usage ccu
ON con.conname = ccu.constraint_name
AND nsp.nspname = ccu.constraint_schema
AND rel.relname = ccu.table_name
WHERE nsp.nspname = #{connection.quote(schema.presence || current_schema)}
AND rel.relname = #{connection.quote(table)}
AND ccu.column_name = #{connection.quote(column)}
AND con.contype = 'c'
ORDER BY constraint_name
SQL
connection.exec_query(check_sql)
end
def cascade_statement(cascade)
cascade ? 'CASCADE' : ''
end
def not_null_constraint_name(table, column, name: nil)
name.presence || check_constraint_name(table, column, 'not_null')
end
def missing_schema_object_message(table, type, name)
<<~MESSAGE
Could not find #{type} "#{name}" on table "#{table}" which was referenced during the migration.
This issue could be caused by the database schema straying from the expected state.
To resolve this issue, please verify:
1. all previous migrations have completed
2. the database objects used in this migration match the Rails definition in schema.rb or structure.sql
MESSAGE
end
end
end
end
end
|