MXS-1299: Fix CREATE TABLE t1 LIKE t2 processing

The creation of tables from other tables was not working even though the
information was available inside the avrorouter.

server/modules/routing/avrorouter/avro_schema.c

@@ -771,6 +771,227 @@ TABLE_CREATE* table_create_alloc(const char* sql, const char* event_db)
     return rval;
 }
 
+static const char* TOK_CREATE[] =
+{
+    "CREATE",
+    NULL
+};
+
+static const char* TOK_TABLE[] =
+{
+    "TABLE",
+    NULL
+};
+
+static const char* TOK_GROUP_REPLACE[] =
+{
+    "OR",
+    "REPLACE",
+    NULL
+};
+
+static const char* TOK_GROUP_EXISTS[] =
+{
+    "IF",
+    "NOT",
+    "EXISTS",
+    NULL
+};
+
+/**
+ * Read one token (i.e. SQL keyword)
+ */
+static const char* get_token(const char* ptr, const char* end, char* dest)
+{
+    while (ptr < end && isspace(*ptr))
+    {
+        ptr++;
+    }
+
+    const char* start = ptr;
+
+    while (ptr < end && !isspace(*ptr))
+    {
+        ptr++;
+    }
+
+    size_t len = ptr - start;
+    memcpy(dest, start, len);
+    dest[len] = '\0';
+
+    return ptr;
+}
+
+/**
+ * Consume one token
+ */
+static bool chomp_one_token(const char* expected, const char** ptr, const char* end, char* buf)
+{
+    bool rval = false;
+    const char* next = get_token(*ptr, end, buf);
+
+    if (strcasecmp(buf, expected) == 0)
+    {
+        rval = true;
+        *ptr = next;
+    }
+
+    return rval;
+}
+
+/**
+ * Consume all tokens in a group
+ */
+static bool chomp_tokens(const char** tokens, const char** ptr, const char* end, char* buf)
+{
+    bool next = true;
+    bool rval = false;
+
+    do
+    {
+        next = false;
+
+        for (int i = 0; tokens[i]; i++)
+        {
+            if (chomp_one_token(tokens[i], ptr, end, buf))
+            {
+                rval = true;
+                next = true;
+                break;
+            }
+        }
+    }
+    while (next);
+
+    return rval;
+}
+
+/**
+ * Remove any extra characters from a string
+ */
+static void remove_extras(char* str)
+{
+    char* end = strchr(str, '\0') - 1;
+
+    while (end > str && (*end == '`' || *end == ')' || *end == '('))
+    {
+        *end-- = '\0';
+    }
+
+    char* start = str;
+
+    while (start < end && (*start == '`' || *start == ')' || *start == '('))
+    {
+        start++;
+    }
+
+    size_t len = strlen(start);
+
+    memmove(str, start, len);
+    str[len] = '\0';
+
+    ss_dassert(strlen(str) == len);
+}
+
+/**
+ * Extract both tables from a `CREATE TABLE t1 LIKE t2` statement
+ */
+static bool extract_create_like_identifier(const char* sql, size_t len, char* target, char* source)
+{
+    bool rval = false;
+    char buffer[len + 1];
+    buffer[0] = '\0';
+    const char* ptr = sql;
+    const char* end = ptr + sizeof(buffer);
+
+    if (chomp_tokens(TOK_CREATE, &ptr, end, buffer))
+    {
+        chomp_tokens(TOK_GROUP_REPLACE, &ptr, end, buffer);
+
+        if (chomp_tokens(TOK_TABLE, &ptr, end, buffer))
+        {
+            chomp_tokens(TOK_GROUP_EXISTS, &ptr, end, buffer);
+
+            // Read the target table name
+            ptr = get_token(ptr, end, buffer);
+            strcpy(target, buffer);
+
+            // Skip the LIKE token
+            ptr = get_token(ptr, end, buffer);
+
+            // Read the source table name
+            ptr = get_token(ptr, end, buffer);
+            remove_extras(buffer);
+            strcpy(source, buffer);
+            rval = true;
+        }
+    }
+
+    return rval;
+}
+
+/**
+ * Create a table from another table
+ */
+TABLE_CREATE* table_create_copy(AVRO_INSTANCE *router, const char* sql, size_t len, const char* db)
+{
+    TABLE_CREATE* rval = NULL;
+    char target[MYSQL_TABLE_MAXLEN + 1] = "";
+    char source[MYSQL_TABLE_MAXLEN + 1] = "";
+
+    if (extract_create_like_identifier(sql, len, target, source))
+    {
+        char table_ident[MYSQL_TABLE_MAXLEN + MYSQL_DATABASE_MAXLEN + 2] = "";
+
+        if (strchr(source, '.') == NULL)
+        {
+            strcpy(table_ident, db);
+            strcat(table_ident, ".");
+        }
+
+        strcat(table_ident, source);
+
+        TABLE_CREATE *old = hashtable_fetch(router->created_tables, table_ident);
+
+        if (old)
+        {
+            int n = old->columns;
+            char** names = MXS_MALLOC(sizeof(char*) * n);
+            char** types = MXS_MALLOC(sizeof(char*) * n);
+            int* lengths = MXS_MALLOC(sizeof(int) * n);
+            rval = MXS_MALLOC(sizeof(TABLE_CREATE));
+
+            MXS_ABORT_IF_FALSE(names && types && lengths && rval);
+
+            for (uint64_t i = 0; i < old->columns; i++)
+            {
+                names[i] = MXS_STRDUP_A(old->column_names[i]);
+                types[i] = MXS_STRDUP_A(old->column_types[i]);
+                lengths[i] = old->column_lengths[i];
+            }
+
+            rval->version = 1;
+            rval->was_used = false;
+            rval->column_names = names;
+            rval->column_lengths = lengths;
+            rval->column_types = types;
+            rval->columns = old->columns;
+            rval->database = MXS_STRDUP_A(db);
+
+            char* table = strchr(target, '.');
+            table = table ? table + 1 : target;
+            rval->table = MXS_STRDUP_A(table);
+        }
+        else
+        {
+            MXS_ERROR("Could not find table '%s' that '%s' is being created from: %.*s",
+                      table_ident, target, (int)len, sql);
+        }
+    }
+
+    return rval;
+}
+
 /**
  * Free a TABLE_CREATE structure
  * @param value Value to free